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Monday, December 29, 2014

What Causes Brown Leaves on Yucca?

Q. Why are the tips of my yucca leaves turning brown? 
Brown leaf tips on yucca. Can be from soil or irrigation problems.
A. This is pretty common on yucca in our climate and soils unless they are grown in filtered sunlight and the soil has been prepared well before planting. They always tend to have brown tips. In the case of your plant, judging from your picture, it does seem excessive.
When we see brown tips on the foliage of desert plants it usually means a watering problem, a soil salt problem or lack of drainage.
This particular yucca is native to the Chihuahuan desert so infrequent irrigation is critical to its health. Most of the soils in the Chihuahuan desert are better than our landscape soils created by the builders of our homes.
Regarding your irrigations, compare your watering with how these plants might be watered in their natural habitat. This is a guideline for how you should water. They won’t need watering that often so if you are watering more frequently than every two or three weeks in midsummer, I would suggest this is too often.
If this plant is on the same irrigation circuit as other landscape plants, and these other plants are not a desert plants, then I would suggest the plant is being watered too often.
The volume of water you give the plant is not as critical as the frequency it receives water. In other words, you can give it a large volume of water and not hurt the plant as long as you wait long enough before the next irrigation. Giving large volumes of water may waste water but it seldom keeps the soil too moist for the plant between irrigations.
If this plant is watered too often, remove it from that irrigation circuit and water it by hand every few weeks. It will like a couple of deep winter irrigations, a spring irrigation, a couple of midsummer irrigations and a fall irrigation and that's about it.
If the applied water is close to the trunk, then the trunk could be rotting. Keep frequent irrigations away from the trunk. However, it is okay to water in a large basin beneath the plant if it is done infrequently.

If there are other plants around it, it is probably getting enough water from its neighbors. But I would still give it an occasional drink to be on the safe side.

Can I Apply Iron in the Winter?

Q. I have a dwarf lemon tree with many yellow leaves. Can I add iron at this time of year (December)?
This is not citrus but it is iron chlorosis. You can tell from the yellowing of the leaf while the veins remain green and appearing on the newest growth. It is possible to confuse it with manganese deficiency easily.

A. If you apply iron this time of year (December) it is best applied as a foliar spray rather than to the soil. If the leaf yellowing is not extensive you could wait until spring. Leaf yellowing reduces a plant’s ability to capture sunlight and produce energy to maintain its growth and health.
Iron chelate made for applying mixed with water. 

If you want to correct it now, you must apply iron to the leaves as a liquid or foliar spray. It is best to use an iron chelate mixed with water and add about 1 tablespoon of white vinegar if you use tap water to reduce the alkalinity. If you use distilled water, you will not need the vinegar.  To this water add the appropriate amount of iron chelate listed on the label. You should add a wetting agent to help the spray penetrate the leaves.
You can make your own wetting agent by using a liquid detergent like Dawn or Ivory Liquid at a rate of about 2 teaspoons per gallon added to the finished spray mix. It is not as refined as a commercial wetting agent but it will do the job.
A very safe wetting agent for better leaf penetration

You would apply this mixture of water, chelate and wetting agent to the leaves immediately after mixing it until the spray runs off the leaf surface. Let the leaves dry and repeat it a few days apart or until you see the leaf color change from yellow to a darker green.
Foliar sprays like these may require several applications to get the results you desire.  Citrus leaves have a very waxy surface and are difficult to penetrate with just plain water. If you use tap water then each time you prepare a new spray you should adjust the alkalinity of the water with vinegar and add a wetting agent.
Foliar sprays should always be freshly made, applied immediately and not stored for any length of time. Unfortunately homemade iron liquids, unlike commercial sprays, do not store very well. It might be cheaper in the long run to buy the liquid iron spray already made and make the application.
It is also possible citrus leaf yellowing could be a magnesium or manganese problem. Liquid iron sprays will not correct problems due to magnesium or manganese.

Radishes Are the Perfect Winter Vegetable for Beginner Gardeners

Radishes are the perfect winter crop for the beginner gardener in the ground, raised beds or containers. They are easy to grow, will germinate at very low soil temperatures and will mature for harvesting in as little as 30 days. Don't plant them too deeply and to speed germination cover with some clear plastic to keep the soil warm. Remove the plastic after you've seen them germinate.

Space the seed in rows or in blocks so that the seed is about 1 to 2 inches apart from each other. In our Las Vegas climate you should be able to get 5 to 6 crops during the fall, winter and spring seasons when they are the sweetest.

Find some hybrid varieties which will reduce the heat or spiciness if you don't like that. The tops can be eaten in a salad or cooked as greens just like mustard greens. The oil that you use in cooking greens has a big impact on the flavor of cooked greens.

French breakfast radish after 30 days

Spacing of radish seeds. If radishes are too close together they will not produce large bottoms.

Brown Ugly Space Alien in the Garden

Recently I found this brown space alien into one of our raised beds. This is the pupa, or resting phase, of the tomato hornworm. This is the stage of development between the worm or larva and the adult hummingbird or sphinx moth. This insect is a voracious feeder of all garden plants but particularly tomatoes, peppers, eggplant and even grapes!

This insect will overwinter in this stage and emerge again in the spring as the adult hummingbird moth. It will find a mate by flying at dusk and lay eggs on plants that it likes to eat. The eggs will hatch into a miniature hornworm and voraciously grow into the much larger version.
Hummingbird or Sphinx moth
Right now you can dispose of them. But later in the spring after planting you will want to protect your plants with either Bt or Spinosad.
Bt can be found under the names of Dipel or Thuricide as well.
One of the names for Spinosad. Check the ingredients

Delay Pruning Grapes Until Very Cold is Past

Q. I usually prune my grapes when I do the roses but would like to get a jump on it this year. Will I do them any harm if I prune them now (December)?

A. You can do it but I worry a little bit about possible freezing damage if these are winter tender grapes and desiccation. Some grapes are less cold hardy than others. For instance, Thompson seedless has some wine grape heritage (vinifera) and tends to be less cold hardy than some other table types.

I have noticed in our desert climate that we can also get winter desiccation (drying out) in windy locations. Those grapes which are pruned to spurs usually leave only one or two buds which means the spur may only be one half inch long after pruning. If we lose this half inch of growth from winter cold or desiccation, then we have lost our crop for the season.

I usually delay it until almost the first week in March when buds are starting to swell. By delaying it I can prune out the dead wood that occurs during the cold winter months and focus on the stuff that is still alive. I would wait.

Swarming Bugs; Ants or Termites?

Q.  We were out in our yard last weekend putting up decorations when we noticed small bugs flying up out of our yard. They were thick groups of them coming out of small holes that looked like grains of rice clumped together in bunches. There had to be thousands of them. The "exodus" lasted for about an hour and then it was done with no sign they had been there.  Can you tell what they are?  Are they harmful?  Do we need to do something to get rid of them?
Flying ants or termites. The length of the wings suggests termites but a visual check of the bodies and antennae need to be done.
A. These look like winged ants or possibly winged termites. It was difficult to tell from your picture. They both swarm in identical fashions. The ants are just a nuisance. If these are termites then you may have a problem.
You need to catch some of these insects and look at their body shape, antennae and length of their wings. Ants have a constricted waist or segmented body parts. Termites do not have these segmented body parts and body parts are not as easy to distinguish. 
I have provided a link on my blog for you to follow or you can type the following into your search engine that will help you identify the difference between the two different insects. 
If you believe these are termites contact a reliable pest control company and schedule a follow-up.

Follow the link below or on my blog to read information about flying ants from Colorado State University. More about flying ants

When Should I Winter Prune Flowering Plants?

Q. I have some bushes and shrubs in my backyard that still seem to be blooming. How do I know when they are ready to be trimmed back?

A. Sometimes we have to prune them back to make way for new growth in the spring. For small plants that get a lot of woody growth at the base, let them go through the winter and trim them back after all of the very cold weather has passed this winter. That is usually by mid-February.
Lantana after winter pruning. This was actually left too long. Prune closer to the ground. After pruning, this is what you will look at until February.

Pruning of ornamentals is all about appearance. If it looks bad to you, go ahead and prune it back. You will not hurt the plant. My major concern about pruning too early is the possibility of freezing damage and creating more work for yourself. If you prune now and we get more freezing weather then you will have to prune a second time.

Waiting until the end of the coldest part of the winter avoids pruning a second time. But if you like to go out in the yard and tinker, prune when you need to. It won't bother the plant.

Saturday, December 27, 2014

Harvest Oranges Before a Hard Freeze

Q. After 6 years, I am finally getting  oranges. They are turning orange and I have been told not to pick them until mid January. Is this right or can I pick them now (mid-December)?

A. Different varieties ripen at different times. I would sample one now and if it tastes good to you then harvest the others at the same maturity. If it is not yet to your liking then wait a bit but if temperatures drop to the mid-20’s then the fruit might freeze. In the Las Vegas area we get our coldest weather NORMALLY from mid-December to the end of January.

Play it by ear a bit right now but normally they would be ready right about now. You do not want to wait too long because fruit remaining on the tree can interfere with new flower production.

I copied and pasted this citrus calendar from the University of Arizona pdf document you can download from HERE. These are the approximate harvest dates (this is for Maricopa County, aka Phoenix area). We are a bit colder so harvest times can be a bit later. However for areas like Laughlin and Bullhead City they would be on the mark.

Note: I am recommending citrus in the Las Vegas area in only warm microclimates or protected from winter cold and winds.

The chart below I copied and pasted from the University of California Riverside pdf document you can download HERE.  This tells you the critical temperatures where you might lose different parts of the tree (flower buds, blossoms, green fruit, ripe fruit).

Monday, December 22, 2014

Will Buffalograss Grow in the Mojave Desert?

Q. Will Buffalograss grow in the desert?

A. Buffalograss grows perfectly well in the Mojave desert. The major problem is finding a source for it. I would not start it from seed if you want a good quality lawn. The best method would be to use sod but without a source of sod locally, you could have plugs shipped in from a reputable supplier.
Buffalograss can make a good quality lawn if you started from sod or plugs but not from seed..
Buffalograss is native to our dry grasslands and prairies of the United States. Like Bermudagrass and zoysia grass, it is a warm season grass which means it will become dormant or go to sleep during the winter months. It is best planted when soil temperatures have begun to warm in the spring or very early summer.

Preparation of the soil is very important for good establishment. Plugs are normally at least 2 inches in diameter and spaced 12 to 24 inches apart in the lawn area. Because Buffalo grass is a sod forming grass it fills the bare soil between plugs with stolons or surface runners. With good management the lawn area should be completely filled before it gets cold in the fall.

This is a bit controversial but research in Arizona has demonstrated Buffalo grass to use about the same amount of water as Bermuda grass but it does not require the fertilizer or the same level of management.

A reputable supplier out of Nebraska is Todd Valley Farms. Give them a call and talk to them if you are thinking about Buffalo grass.

Can I Grow Persimmon From Seed?

Q. I had a couple of persimmons from a friend's tree in California. Can I plant these seeds from this fruit and if so do the trees thrive here?

A. Yes, persimmons will grow in the desert with a little bit of extra care. Our desert soils must be amended with compost before planting. After planting, persimmons will perform best with a surface mulch of 3 to 4 inches of wood chips. Persimmons perform very well if you fertilize with compost once a year.
Persimmon leaf size with organic fertilizers like compost applied to our desert soils.
You can grow persimmon from seed easily but these trees will not be exactly the same plant as your friend’s. A tree from these seeds might have better fruit or the fruit might be worse.

To germinate, persimmon seed must go through about two months of cold, wet conditions,Similar to the conditions it would find in nature. In nature the fruit matures in late fall or early winter and drops to the ground in a layer of natural surface mulch or debris. In this surface mulch it spends the cold winter. In its native environment this surface mulch would stay relatively moist compared to our dry desert winters. 
Hachiya persimmon grown in the desert that is nearly mature. At this stage the seeds can be harvested but the fruit will not be quite at its peak of ripeness and will still be astringent.

You can simulate this by using a refrigerator. Refrigerator temperature is fine but the seed should be kept moist but not wet. These conditions remove inhibitors in the seed coat that may keep it from germinating. Make sure the seed is clean and pack them in ever-so moist sand before putting them in the fridge. This should not be in plastic bags but something that can "breathe" while in storage. You need to moisten the seed's environment periodically.

After the two months and freezing temperatures have passed, you can plant these seeds directly into amended soil in the garden area or in a container.

Alternatively, plant them directly into amended soil in the garden or container, moisten the soil, mulch it with 2 inches of wood mulch and water about once every 3 weeks during the winter. They should germinate in the spring in the spot where you planted them when the weather warms.

Sunday, December 21, 2014

Saving Bougainvillea From Freeze Damage

Bougainvillea summer time
Q. While most of our bougainvillea are in large pots which we bring indoors for the winter, this year we planted one in an above ground planter built around the Jacuzzi. What should I do to help it survive the winter without having to dig it up and transplant it again in the spring?

A. Your bougainvillea will have a better chance of surviving the winter planted in the ground than it will planted in a container. However, expect it to be damaged this winter unless you are willing to apply heat to the area where it is planted and cover the plant all the way to the ground.
Bougainvillea that has frozen back during winter
If left unprotected, your bougainvillea will freeze to the ground as soon as temperatures drop below freezing. If temperatures dip quickly below freezing and rise above freezing in a short period of time, damage will be light. If temperatures dip below freezing and stay there for a while, the entire top of the plant above ground is likely to freeze and die.
The death of the top of the plant is not necessarily a big problem. The dead parts can be pruned back close to the ground and encouraged to regrow in the spring. My major concern is protecting the base of the bougainvillea, near the soil, so it can regrow.
Some inexpensive insurance is to pile several inches of mulch around the base of the plant just before it freezes. This wood mulch acts as an insulator which protects wood at the base of the plant from dying. Of course if temperatures get unusually cold for long periods, it is possible to lose the entire plant. But in most winters this will not happen if mulch is used.

In mid-March prune out any damaged plant parts back to healthy wood. Fertilize the plant with a high nitrogen fertilizer and water deeply. After it has re-grown significantly, apply a phosphorus fertilizer either to the soil or spray and liquid on to the foliage.

Thursday, December 18, 2014

What to Do Before the Freeze Comes

We already had a taste of freezing weather back in November in some parts of the Valley. Unless this is a very unusual winter, more is coming. In Las Vegas we can expect nighttime temperatures to drop into the mid to high teens degrees F (-10C).

  • Rarely does the soil freeze more than a couple of inches deep. 
  • The coldest time is just before sunrise. 
  • Clear, cloudless nights will be more likely to give us freezing weather. 
  • If you think it might freeze, go outside at night and see if the night sky is clear (cloudless).
  • If you cover plants at night, uncover them the next day as soon as the temperatures are no longer freezing.
  • Water the day it may freeze or make sure the soil is wet going into freezing temperatures.

Check weather forecasts. Look for future minimum temperatures AND WIND!!!

I like Weather Underground for the wind reason and you can see it here and bookmark it.

Protect from the wind. Remember, cold is bad enough but when it is combined with wind it will be much more damaging. Protect anything of value or that can freeze and cause damage by first blocking the wind. This can be as simple as throwing a light blanket over a tender plant or a thick blanket around pipes that could freeze.

Wrap pipes totally. Remember that metal freezes quicker than plastic. Plastic pipes will freeze but any metal fittings exposed to the wind will freeze more quickly and be more expensive to replace. It is always best to wrap exposed pipes with insulation starting a couple of inches below ground. Wrap ALL exposed metal parts above ground. Leave nothing exposed to the wind.

Drain pipes. If the pipe and metal components don't contain any water, they are less likely to be damaged when there is a freeze. Drain pipes by opening irrigation valves after you shut off the water to your irrigation system. Shut off the water to the valves and loosen the bleed screw on top of the valve or loosen the solenoid 1 1/2  turns (not all the way!), enough so water squirts out from the solenoid or bleed screw.

Protect Tender Plants. A good resource on protecting plants from winter cold was published by the University of Arizona. You can find it here.

Plants that you should consider protecting at the first sign of a freeze include: limes, lemons (not Meyers), and citron, bougainvillea, many hibiscus, pygmy date palm, plants that are flowering. Don't cover plants with plastic. The cold plastic touching the leaves can damage them.

Mulch. Put a 3 to 4 inch layer on top of the soil surrounding the plants during the day when the soil is warm. Mulch helps trap soil heat and keep it from freezing. Plants that might freeze to the ground (Lantana) will have a couple of inches of stems protected from the cold and wind with a mulch.

Container Plants. Container plants should be moved into the garage or the plant+container should be covered all the way to the ground. Remove the cover when temperatures are no longer freezing.

Lawns. If the lawn has frost or is frozen, DON'T WALK ON IT. Walking on frozen grass will damage the blades and leave footrpints due to the damage.

If damage does occur..... do not prune out the damage until all cold weather has passed.

Damaged Cactus Edges Probably Rabbits

Q. I have a cactus that has small flat paddles with no visible needles. The problem it has is that all of the paddles seem like they are chewed around the edges. Every time a new paddle grows, the edge soon becomes brown around the edges.

A. This is most likely rabbit damage. Just because you don't see any needles doesn't mean they are not there. There are plenty of cacti that seem to have no needles at all. But they are small and even more of a problem for humans and other animals than cacti with large needles simply because you are not as cautious around these types.
Rabbit damage to nopal cactus with very tiny spines
One primary reason for having needles, and particularly large needles, is to prevent animals from eating the pads. The spines, or needles, on cacti are at locations on the plant which are not random. If you look at them closely they follow a spiral pattern with spaces between them.
Nopal Cactus with large spines
When a plant has large spines or needles it helps prevent the animal from getting close enough to take nibbles. The smaller the spines, the closer animals can get and chow down.

Rabbits love cacti with very small spines. They will eat between the spines being very careful not to let their mouth come in contact with them. Of course the easiest place for them to chow down is on the margins of the pads, between the spines.

You most likely have rabbit damage and you will have to exclude them from the plant if you want to keep them from getting damaged. Chicken wire in 24 inch widths with 1 inch hexagon openings will keep rabbits away from these plants if they are put around the perimeter. Make sure the rabbit cannot put its nose under the bottom edge and get under it.

What Are These Weird Growths in My Oleander?

Q. A backyard grouping of four, 12-foot high oleanders that are 18 years old have very strange growths sprouting from the branches so I sent you a picture. Some trees have dry branches.  Others show sections of normal-looking leaves. Meanwhile, a dozen other oleanders look normal. My initial thought was that the strange group of four was not getting the proper watering.  So I have been giving those some extra shots.  But haven't noticed much change since the extra watering started about six weeks ago.

Readers witches broom of Oleander
A. Those clusters of strange growth coming from the stems are most likely witches broom of oleander caused by a fungal disease. It is often spread by pruning shears from plant to plant. It can also spread within the same plant or passed on to new plants when propagated from cuttings.
Witches broom also causes leaf tips to die back but it is usually recognized by those clusters of shoots coming from buds below the pruned area. Usually these distorted shoots grow a few inches and then die.

You may not see these symptoms show up for a couple of months after pruning have been done. This disease is also spread by insects and rainy, windy weather.

There are no chemicals that will control this disease. I would recommend that you cut severely infected plants a few inches above the soil this winter and let them regrow from the base. Make sure you sanitize your pruning shears. If you have some plants there are showing some leaf tip burn then cut these back at least 12 inches below the area showing these symptoms.

Do you want to read more about whitches broom? Click on this link.

Where to Plant Pear, Apple, Quince and Citrus

Q. I'm thinking about adding pear, apple, quince, grapefruit and blood oranges to my landscape and I'm wondering if you could give me advice as to the best place I can put these guys. I would like to espalier or trellis the quince.

A. The major limitation for all of these fruit trees is going to be winter cold temperatures for the citrus and summer high temperatures and reflected heat and light. In this part of the Mojave desert at a 2000 foot elevation most citrus trees, if not all of them, should be grown with care. This is not citrus country but if they are placed in the right microclimate they can be productive and healthy for many years to come.

East is a good exposure for quince because it tends to sunburn and get borers in full sun all day or hot locations. 
Pineapple quince with fruit in Las Vegas
Any of these fruit trees can be trellised or espaliered and suitable for side yards.
Apples and pears can handle full sun in open areas such as backyards if the soil is amended at planting and a four to six inch layer of surface mulch is applied to the soil beneath the canopy.

Apple trellised or espaliered in Las Vegas.
As far as citrus goes, you need a warm spot in the yard with little winter wind so they are protected from damaging winter cold and hope for the best. All of the citrus you like are tender to winter weather here but you will have the best luck with the most cold tolerant types of citrus such as kumquat, Myers lemon and grapefruit. 

Go to this website to learn about citrus varieties for the desert Southwest

White Fuzzies on Cactus Probably Cochineal Scale

Q. I planted a "cows tongue" or sometimes called "angel wing" cactus last spring and over the summer it began to develop some white cottony looking growth around each of the spines on the lower pads.  The white growth has continued and now covers much of the pads and some of the lower pads have actually fallen off. What is this white growth?  Is this a common problem with the cows tongue or is it common to all padded cacti and if so what can be done to rid the plant of the growth.  Someone had mentioned that it could be because of my watering schedule.  What do you think?
A. I don't have a picture of this problem on your cactus so I am following the KISS (Keep It Simple Stupid) diagnosis technique. The stupid part is to remind me that nine times out of 10 it is a common problem, not a rare event.

This is most likely problem is Cochineal scale, a common problems on cacti.
Heavy infestation of cochineal scale on Opuntia cactus.
If you touch it and it leaves a blood red liquid on your finger it is Cochineal scale. Both are scale insects hiding under that cottony growth and feeding on plant juices. When they reproduce and their populations increase, the feeding damage is so great it causes the plant or parts of the plant to collapse and ultimately die.
The red dye produced by cochineal scale when it is damaged. Notice how cochineal scale is commonly found close to the spines.
For either of these insects the control measures are the same. You can take a cotton swab and dab each of the cottony growths with alcohol or apply a systemic insecticide to the soil such as those containing imidicloprid so the poison will be taken up by the roots and moved to where this scale insect is feeding thus killing the insect.

The cochineal scale has an interesting history in Central America where this red extract was valued by Spanish colonizers as a dye until it was replaced by synthetic dyes. The actual insect was a very close relative of the Cochineal scale we see in our landscapes now. 

Tuesday, December 16, 2014

Remove Bottom Leaves in Cabbage to Reduce Pest Problems

Q. What can I use for bugs on my cabbage now?

A. The usual bugs on cabbage are aphids, whiteflies or cabbage looper. First off, remove the bottom leaves on the plants near the ground. They are nearly in full shade and no longer contribute much to the plant.
Cabbage leaves too close to the ground and cannot be sprayed on the underside. Most bugs will collect on the undersides of the leaves.
Once the lower leaves are removed it is easier to spray the bottom of the leaves, pointing the nozzle upwards.
These leaves are close to the ground, the underside is a great place for bugs to hide from predators and impossible to spray. In older plants they are tough so you will need to cut them off.
These insects also like to gather between leaves at the base. This is where you find cabbage looper eggs deposited. This is the white butterfly that likes to hang around cabbage and cabbage related vegetables, lay eggs that hatch into green worms that chew holes in the leaves.
A sure sign of insect problems are holes in the leaves. The plants should be sprayed at the first sign. Cabbage butterfly lays its eggs deep inside the crevices of the leaves. This area needs Bt or Spinosad sprays or dust.
You should have on hand at three to five of these organic sprays; insecticidal soap, Neem oil, Bt, pyrethrin and Spinosad and a good pump sprayer. Soap sprays will be used most often; twice a week. The others are applied less often, usually as needed.
Spray on top of the leaves as well as the undersides where most insects will hide and feed. Bt sprays like Dipel or Thuricide are used against pests whose adult forms are moths such as the cabbage looper. This spray or dust is applied between the leaves and left undisturbed for a few days so it can work.
Some insecticides say Bt right on the label while others may say Dipel, Thuricide or worm or caterpillar killer.

Whiteflies are controlled with insecticidal soap, pyrethrum or Spinosad sprayed alternately, a few days apart. Sprays need to be directed at the pests so it must be applied to tops and bottoms of leaves.
A popular brand of insecticidal soap

After harvest you will still have bugs in the cabbage and other leafy greens. A rinse in a clean sink with water containing 1 tablespoon of household bleach per gallon will kill any bugs remaining. Rinse all vegetables with clean water before preparing them.

Monday, December 15, 2014

Pyracantha Good Choice for Moderate Water Use Landscape

My only comments are that this can be fairly prone to borer problems if put into full, intense desert sunlight so that the sun damages its thin bark. There are definitely some varieties that birds like more (fruit) than others. Some varieties birds (Mockingbirds in particular) just won't touch. There are some varieties where the fruit can be made into pyracantha jelly. Google it. Other varieties have no flavor at all or sweetness and hence birds don't like them. Make sure you get pyracantha that have sweet berries if you want to fight with the birds over who gets them. Try them to see if they are sweet or not.

The colloquial name "firethorn" refers to the stinging sensation you can get when the thorns puncture your skin. It is not poisonous.

The fruit is closer to an apple anatomically (of course a very tiny apple) than a berry.

It can get aphids, spider mites, iron chlorosis and cotton cushion scale. It is in the rose family so it is not a desert plant and does best with wood surface mulches. It will get root rot if the soil is kept too went or the soil does not drain easily.

Creosote Bush, Mojave Native, for Desert Landscapes

Be very careful in watering these plants. They will die easily if they are watered too often or fertilized too much. They have a tendency to be a "nurse" plant for others in their shadow.
Creosote in the front and back. The difference? The ones in the front were along a desert road and were cut off by a road grader. The ones in the back were not and got woody. That's the secret if you want them small and bushy. Cut them to the ground when they are established and let them regrow.

Moringa Symposium in Manila Philippines Next November

International Symposium on Moringa

Manila, Philippines, 15-18 November 2015

Date of the symposium has been changed to 15-18 November 2015 (instead of 19-22 November 2015)!

For more information please go to http://www.ishs.org/symposium/488

Further details can be found in the brochure as well at http://avrdc.org/download/workshops/moringa%20brochure_REV7_FINAL.pdf

International Society for Horticultural Science PO Box 500 - 3001 Leuven 1 - Belgium
Phone: +32 16229427 Fax: +32 16229450

check out http://www.ishs.org/calendar for a comprehensive list of ISHS meetings

Harvesting the Sun - A Profile of World Horticulture by ISHS http://www.harvestingthesun.org

Get in touch:
If you'd like more information on a particular meeting, get in touch with the convener of the symposium.
For a specific query, to check out our FAQs or to contact ISHS go to www.ishs.org/contact

Why did I post this? I LOVE moringa (mulungay). It has a wonderful flavor for shrimp and meat dishes particularly cooked with coconut milk and hot peppers!

Sunday, December 7, 2014

Pruning Oleander Correctly Is Very Simple

Q. I purchased dwarf oleanders two years ago in five gallon containers. They are doing fine but are about four feet high. It is my understanding the plants can be pruned. I need to know the best time to do so and how far down to go without harming them.

A. Pruning oleander is very simple, much simpler than many other plants. You can prune them any time of the year without any problems. Having said that, they are usually pruned during the winter, late winter or very early spring.

Prune them with a loppers; the one that has two handles and you have to use both hands. Count the number of main stems coming from the base of the plant. Identify the two or three that are the oldest. They will be the largest in diameter.

 Remove these oldest ones within a couple of inches above the soil. You are done for this year! It takes about ten minutes and no mess to clean up! If there are some unusually long ones remove them from the base as well.

Repeat this about two or three years later. Continue this cycle of removing the largest diameter every three years or so.

Please do not use any hedge shears unless you don’t like the flowers. Having said all this, the absolute best time to do this in southern Nevada is February but you can do it any time without damaging the plant!

Euonymus Plants Have White Spots and Dying

Q.My euonymus plants are dying. These are all plants that have been in the ground 8-10 years. Now, they are getting a white spot on their leaves and shortly afterwards the plants die. The plants in my backyard did this last year, and now plants in the front have the same symptoms. Some people said they needed more water. That didn't do anything for the white spot. I tried cutting off the spotted leaves. That might help, but I am not sure. Is there anything I can spray or dust the plants with to stop the fungus?

Powdery mildew and leaf death. Powdery mildew is deeper inside the canopy were it is shady.
A. I am not sure what you mean by a white spot, whether this white spot can be rubbed off or whether it is permanent. These plants do get powdery mildew which looks like leaves have been dusted with white flour in some locations.This disease occurs on plants in shady locations.

If it is powdery mildew it usually means they are not getting enough sun or the canopy of the plant is not open enough for air movement. Powdery mildew, unlike other fungal diseases, requires very little humidity to become a problem. It is spread by splashing water from overhead irrigation hitting the leaves and splashing on others carrying the disease to these leaves and so it spreads.
You can buy a dust or spray to control powdery mildew but that just circumvents the problem and it will come back. The long term way to control it is to get more sun on the plants (move or prune them to open the canopy up), improve their health with fertilizers and appropriate watering. If the plant is under watered the canopy will be very open and I doubt you would have powdery mildew unless it is in shade or partial shade.
A white spot can also mean scorching of the leaves due to direct intense sunlight. This type of damage cannot be rubbed off with your fingers. It is permanent damage to the leaf. If this is the case then the plant may be in the wrong spot (intense sunlight or lots of reflected heat and/or light from windows and a west or southwest exposure and planted in rock.
 If this is the case then you need to move it away from this intense location into one that is more cooling with less intense sunlight. This is not a desert plant and cannot handle this kind of exposure. It does not like rock mulch very much so put it in organic mulch on the soil surface.
If it has only one drip emitter, put two or three depending on its size. If you are watering every day then water deeply every other day or every third day now. Make sure you fertilize this plant in the spring with a good tree shrub fertilizer.

If you want to move this plant, you can move it to a new location in October, moving as much of the soil with it as possible, and mulch it. Predig the hole and move it and plant it in less than 30 seconds once the roots are exposed.
Euonymus does much better with a wood surface mulch.Neem oil is a pretty good organic control for powdery mildew.

Why Does My Orange Tree Have No Fruit?

Q. I have a dwarf orange tree planted a little over a year ago. There have been no oranges on the tree. I have fertilized and I think I've been watering it correctly. The tree appears to be healthy just no fruit. Any suggestions?

A. Dwarf orange is not much help to me. The subject of oranges is huge. I need to know what type of orange it is, whether it has produced flowers or not and no fruit, or no flowers and no fruit. Varieties vary from early ripening - about 8 months from bloom - to late - up to 16 months from bloom.
There are three main groups: The normal fruited, without navels and with light orange colored flesh; the navel oranges, with a distinct navel development at the end; and blood oranges, with red flesh and juice.

There are about 73 varieties but US production focuses on Valencia, Washington Navel, Hamlin, Parson Brown, Pineapple and Temple. For home gardening there are many more than these six available from nurseries.

Remember, in southern Nevada growing citrus is marginal. Our winters or just too cold. That is the major limiting factor. The usual reason for not producing fruit are winter freezes.

Citrus should be planted in protected areas out of winter wind. They should be protected in the wintertime from cold. There is an excellent publication from Arizona on protecting citrus from cold weather.

Discouraging Root Growth Around Irrigation Pipes

Q. Having had several somewhat expensive repairs because of root damage to my sprinkler system, I am wonder if you have any suggestions for preventing/lessening such damage. I was told by one sprinkler technician that putting copper (he suggested pennies) in the ground would discourage root growth in the area. Is there any truth to this?

A. I am guessing the root damage was lifting the pipe out of the ground because roots were growing under the pipes. Roots will not grow into pipes unless there is existing damage to them, allowing for their entry but then there would be water everywhere. The other type of intrusive growth would be in drip irrigation emitters.

The best ways to avoid damage are to bury pipe deep, plant woody plants far enough from irrigation pipe so that it does not become a problem (preferably outside the irrigated zone of the plant) and use the appropriate type of irrigation pipe.

The best way to keep roots from lifting pipe and damaging them is to bury the pipe deep, as it should be. Irrigation laterals (pipe coming from irrigation valves directly to a sprinkler or other type of emitter) should be a minimum of twelve inches deep (0.3m).

Irrigation lines that are under constant pressure (pipes before the valves) should be a minimum of 18 inches deep (0.5m). All plastic pipe used for irrigation should be a minimum of Class 200 PVC when installed after or downstream of the valve. All pipe under constant pressure (before the valves) should be Schedule 40 PVC.

Class and Schedule refer to the internal pressures that these pipes can withstand which is related to the thickness of the walls of the pipe. All pipe installed should be "fresh" pipe, undamaged by the sun.
Class 200 PVC pipe on the left and Schedule 40 on the right
The PVC in most irrigation pipe is rapidly damaged by the sun if left exposed to it. You will see this damage by discoloration of the pipe. In extreme cases it will turn the PVC black from discoloration due to damage. Once this damage from the sun occurs, the pipe becomes very brittle and has no capacity for bending. It will shatter easily if bent.
Sun damage to white PVC irrigation pipe

Do not use, or do not let a professional use, PVC pipe which is discolored. Pipe exposed to the sun should be painted or wrapped. Paint will protect PVC from the sun's damaging ultraviolet radiation.
As far as pennies are concerned. This idea comes from the fact that copper is very toxic to plants.

Copper sprays are used to control some fungal diseases (Bordeaux sprays), copper is used to control mildew which are plants, copper is used to control algae and mosses which are plants, copper will kill plant roots when used as an appropriate pesticide (yes, it is considered a pesticide if it kills plant roots!) and copper nails will kill trees if pounded into the trunk a few inches apart.

The copper that kills is called elemental copper and must be available to react with plant roots. Perhaps plant roots in direct contact with pennies will be killed but plant roots just a few inches away probably will not. This would mean that if you were to protect the pipe you would have to line the pipe with pennies.

Just a side note. Whenever we pound anything into a tree we need to make sure the damage is minimal. Of course pounding anything into a tree damages it but some things are more damaging than others. Zinc galvanized nails will damage a tree more so than stainless steel. Whenever anything is put into a tree it is always best to make sure it is stainless steel if it has to be done at all. 

Oleanders In Containers Not Blooming

Q. I have two pink dwarf oleanders planted in 18 inch clay pots which are healthy looking but very few blossoms. One of my “expert” friends says simply that "oleanders don't like pots". Another "expert" says that I'm watering too much. Are either of these guys right or do you have any suggestions that might get some some blossoms?

Oleander flowers
A. We have dwarf oleanders at the Research Center in containers and they bloom just fine. The usual reasons for a lack of flowering are not enough light and pruning them incorrectly. Oleanders use a lot of water when it’s present.

There might be a couple of things you could try. Oleanders should be in full sun. They love the heat, and they love water and fertilizer to perform their best.

If the container is smaller you might have to water more often. 18 inch containers are not that large and don’t contain a lot of soil. If the soil volume is not large, the plant may not have enough water in the soil to last between irrigations.

Oleanders that are not getting enough water will look normal but have a very open canopy and not bloom well. Containers are not very forgiving when it comes to water. The water in that soil can be used up fairly quickly.

You can try using a soil moisture meter that you can buy from the nursery for about $7 and check the soil moisture before you water. Water when the meter is about half way between wet and dry, do not let the soil go totally dry.

Next, use a fertilizer like Miracle Gro or Peters and water it into the soil about once every six to eight weeks. Oleanders growing in the ground do not need to be fertilized as often.

Next, cover the soil in the container with mulch to help keep the soil moist. About three inches would be enough.

If oleanders are young or if they are pruned with a hedge shears they will not produce any flowers or very few. Don't prune it with a hedge shears if you want flowers, contrary to how you see it done around town. 

Will Eggplant Produce Through Fall and Winter?

Q. Will my eggplant plant continue to produce through the fall and winter?

Thai purple eggplant

A. They are warm season vegetables so they slow down considerably as temperatures drop.
Although eggplants will keep growing and flowering, they are more productive if cut back and allowed to regrow during late summer. Cut plants to about 6 to 8 inches in early August, cut at a crotch, fertilize and allow them to regrow.
Fertilize and keep soils moist to force them to regrow. The second crop will be ready to harvest in about six weeks after cutting them back. In Louisiana, eggplants are sometimes trellised and sheared late in the season for increased yield and quality.
The ideal temperatures for eggplant is 70 to 80 degrees F in the day and 65 to 70 F at night. Very few places, outside of a greenhouse, gives those types of temperatures consistently. Obviously, they do well in temperatures higher and lower than this. Fruit abortion can begin around 95 F even though the plant itself can handle heat.
Eggplant flower

As temperatures drop in the fall, eggplant still sets fruit but fruit set is not as reliable and fruit development is slower. Eggplant is generally more sensitive to cooler temperatures than its cousins, tomatoes and peppers.
Flowers consistently set fruit down to 60 F nighttime temperatures. Eggplants begin to get chilling injury at temperatures below 50 F.
Staking may be necessary if plants get big and full of fruit. Fruit touching the ground will spoil. Harvest fruit when they are one third full size and shiny. Over mature fruit will be spongy, the seeds begin to harden and the fruit surface becomes dull rather than shiny.

Snap fruit off of the plant but they will keep longer if they are cut from the spiny stem. Mulching helps fruit to set and improves fruit quality.