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?

Click here to see cows tongue cactus

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. 

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.

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

http://www.ishs.org  

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!