How to Get Rid of Unnamed Weed in Lawn

Q. My front and back lawn were taken over by what I call small, nettle-head weeds. Walking on them barefoot remind me of sand spurs that I saw in the South. I have been told it was Bermudagrass weed and chickweed but it doesn’t look like the pictures of chickweed I’ve seen.  Could you please identify them and tell me how to get rid of them?

Pictures of the weed sent to me.

A. I could not recognize the weed from the pictures you sent. Maybe one of the readers will recognize it. It has been cut back severely. This weed appears to have a long taproot like dandelion so it could be one of the local thistles like Bull or Desert thistle. Whatever it is, it has a strong central taproot. This tells me it grows for more than one growing season and is probably a very poor competitor for space in your lawn.

Mechanical Weed Control

            Not the easiest, perhaps, but the best way to rid the lawn of this weed is to cut through the central taproot with a sharp knife, or forked asparagus knife, just below the soil surface. Regrowth of this weed is from the “crown” located at the top of the taproot so cutting the taproot below this prevents it from regrowing and eventually kills it. After an irrigation, perform the coup d’état.

Cultural Weed Control

            Thistles of all sorts are difficult to control with weed killers. But nearly all weeds can be kept out of lawns by increasing the grass density. This is done by mowing high at two and a half to 3 inches, or the top setting of the mower, and fertilizing the lawn regularly. Fertilize lawns at least four times each year with a good quality lawn fertilizer. If the lawn is tall fescue, fertilize on Valentine’s Day, Memorial Day, Labor Day and Thanksgiving. High quality compost can be substituted and gives better results and needs applications less frequently.

Chemical Weed Control

Triclopyrere to guess on the herbicide chemistry that might work on this weed, I would guess something okay to use in lawns but has some woody broadleaf weed control in it. This would be a mixture but I would look for either triclopyr (Garlon) or Dicamba (Banvel) in its list of active ingredients.

Spring Slow Growth of Tomato

Q. I planted Roma, Better Boy and Early Girl tomato varieties this spring. Over 45 days later they've not gotten much bigger than when I brought them home from the nursery. 

A. Be careful when mixing woodchips or other woody soil amendments in the soil. These woodchips require a lot of extra nitrogen as they decompose, a.k.a., rot. They will slow growth and cause yellowing if mixed in the soil without any follow-up nitrogen fertilizer applications. It is very important to add extra nitrogen fertilizer to the soil if you decide to mix anything in the soil made from wood products.

            The weather has been colder and wetter than normal. This has also slowed down the growth of warm season vegetables like tomatoes, peppers, eggplant and the like. Be patient.

Wall o water has been around for a long time and it works a little better than hot caps but more expensive. Be sure to warm the soil before putting transplants out in wall of water or cold soils will slow them down.

            Hot caps aren’t used much anymore but those along with Wall-o-water plant sleeves were made to speed up the growth of plants during cool weather. Rediscover these nifty little garden additions. They keep plants warmer and speed the growth of warm season vegetables when weather is cool.

            On the remote chance something else might be going on, inspect some roots of these plants and see if there are any small “balls” growing on them. 

Root knot nematode on tomato

If found this might indicate nematodes are in the soil and a problem. Nematodes infesting plant roots can slow them down as well. Not much you can do if they are present except replace the soil and plants. This is one reason container gardening can be worthwhile. The containers can be sanitized and the soil replaced more easily than in a garden bed.

Reattaching Vines to Painted House

Q. Last week I pulled the vines growing up the sides of my house in order to paint the exterior. These vines included hacienda creeper, Mexican creeper, Senecio, and creeping fig. Is there anything I might do to encourage them to reattach themselves up the wall or must I cut them back to the ground and wait for them to start over? 

Vines for the desert Southwest

If you're looking for some vines for our hot desert climate, take a look at this pamphlet from the University of Arizona for suggestions. Pay attention to the exposure they recommend, north south east or west, shade or no shade, and the temperature they can tolerate. You are playing with fire if you select anything over 25°F for its cold, winter temperature tolerance.

A. Cut them back and they will grow back quickly to their original size. This is because they are already established. Hacienda Creeper and climbing fig should climb up the painted wall again and reattach to the house on their own. These plants have established roots so they should grow up the sides of the house quickly. Creeping fig is perhaps the slowest grower of the group, but it will reestablish itself over time.

            Pull some of the stems toward the wall as they reemerge and they should start climbing. Cut off stems that don’t reattach and those that do will climb faster. Senecio and Mexican creeper are twining vines so they will need some help climbing again. Adequate water, small amounts of compost once a year and regular fertilizer applications will push them to climb faster.

Neglected Peach Tree on Purchased Property – What to Do?

Q. We bought a property in Redding, California, and it has a pretty sad looking peach tree on the property. Many of the limbs are dead and the live ones are dripping sap. Do we need to get rid of this tree? Is there any way to prevent this from happening again?

Not the peach tree in the question but this peach had borers in the trunk and tried to heal the damage. Note the "rolling" of growth over the damaged area.

A. Peach trees are magnets for wood boring insects, a.k.a. borers, in our climate. This is the main reason most peach trees are not as long-lived as other fruit trees. This insect never enters the soil, so the soil is usually not a problem. Only the tree. If the damage to the tree is severe, remove and replace it.

This is borer damage on a young Bramley Apple tree. Frequently the first 2 to 3 years are critical times for tree establishment and prevention of borers. Damage like this is usually on the West or South sides of the tree because of intense sunlight from those directions. Painting the tree trunk with dilute white latex paint is one option for decreasing borer problems during the first few years. It keeps the trunk a little bit cooler.

The Death Spiral

            Once trees are attacked by these types of borers, the tree frequently enter a death spiral and there is not much you can do without using insecticides. Even applying an insecticide is not a guarantee the tree will be cured. Applying a systemic insecticide containing Imidacloprid as a soil drench soon after flowering may kill borers still inside the tree and give the tree some protection for a few months.

Another indicator of borers in fruit trees is the death of a limb or limbs beginning in about July. Death of a limb due to borers opens the tree for more sun damage followed by borers and can lead to the death spiral I mentioned earlier.

Limbs Die during Summer Months

            Limbs dying because of this insect are normally seen during the summer but the damage they cause inside the tree starts in the spring. These insects are attracted to trees damaged by intense sunlight, but sometimes they infest trees that appear not to be damaged at all. As added protection, make sure the tree is pruned, watered and fertilized so that it has a full canopy which protects its limbs and trunk from intense sunlight. It also helps to shade the trunk or paint it with diluted white latex paint.

Sometimes this damage can be scraped or cut away with a sharp, sanitized knife and the area allowed to heal. It's worth a shot.

Irrigation

            Make sure the tree is getting enough water by irrigating it with at least four drip emitters spaced under the canopy. With newly planted trees, these emitters should be about 12 inches from the trunk in a square pattern and more emitters added as the tree gets larger.

Vegetable Seed Germination Temperatures

Vegetables – for Every Season There Are Vegetables

Q. I planted two rows of corn, separated by some peas, but one row closest to the fence never came up. I replanted that row and now one row of corn is really struggling while the other, closest to the peas, is doing well.

Corn is pollinated by the wind, not insects. A lot of corn plants close together will increase the amount of pollen in the area and improve the chances of having ears that are full rather than spotty.

A. Amend the garden soil with compost to improve drainage. Poor drainage can cause a lack of germination. Lightly dust the seed with Captan fungicide to improve seed germination when planted in cold or wet soils. Tear a corner of the seed packet and place a small amount of fungicide inside and shake it. Always wear gloves when planting seed treated with a fungicide.

My staff in Afghanistan treating wheat seed for better germination. Protect your hands and your mouth when handling fungicides used for seed treatment.

            I strongly encourage you to not plant the same type of crops in the same area as previous years. Instead, plant in new locations in the garden bed and rotate them back to this spot only after 3 to 5 years. This technique helps keep plant diseases minimized.

Planting sweetcorn in raised beds requires the right time of year, a good plant density for pollination. Here sweetcorn is planted 12 inches apart in blocks.

            Mixing woodchips into the soil before planting can also cause poor seed germination. Corn needs lots of nitrogen fertilizer when it’s growing. The rotting of woodchips in the soil also requires a lot of nitrogen fertilizer so make sure enough nitrogen fertilizer has been added to the soil to fuel both growing corn and rotting wood chips.

Corn is more closely allied to grasses than other vegetables. Like grasses, corn is a heavy feeder of nitrogen fertilizer. A slight change in the color green in the leaves will tell you if nitrogen fertilizer should be applied. Let the plant tell you.

            Peas are a winter crop while corn is a summer crop and they should not be planted at the same time in the spring unless you are prepared for a short harvest of peas. Also, sweet corn needs more than two rows planted for for its kernels to fill out the ears properly because it is wind pollinated. Plant at least four rows of corn rather than only two. Plant corn in small blocks rather than rows if the area your planting is small so the ears fill out better.

Cornsilk receives the pollen shed by the top of the plant. If temperatures are too high, poor pollination results. This is seen by missing kernels in the ears. Each kernel is connected to a silk. Every silk must receive pollen for a full ear of corn.

            Both corn and peas have large seeds so try presoaking large seeds, sometimes called pre-germinating, before planting to get faster germination. They should soak long enough for the seeds to swell with water. Soak large seed in tepid water for several hours before planting. This allows the seed to start the germination process without planting. But it’s important to plant them at the right time of year; peas in the fall through winter months for a winter crop and corn in mid spring or late summer for an early summer or fall crop.

This is where the pollen comes from at the top of the plant called a tassel.

            When pre-germinating seed, mix a small amount of your favorite water-soluble fertilizer into the fresh water, along with a tiny amount of liquid soap. This speeds up germination. When seed absorbs water at the very beginning, called imbibition, the fertilizer will be taken inside the seed with the water and early growth is more rapid.

This is what everybody hopes for, a full ear of corn. This is a variety called Silver Queen. It's a lot of work to get here.

Woodchip Epidemic

But Woodchips Are Good!

I think there is an epidemic going on of people adding woodchips to the soil as a amendment. Woodchips applied to the soil surface as a mulch is okay but mixing these into the soil can lead to problems if you aren’t careful. 

Part of this trend is fueled by social media like YouTube and Internet discussion groups and experimentation by gardeners with concepts such as Hugelkulture. It works but it must be done correctly.

Tomato failure. Why? Woodchips.I would not add woodchips to an area that has to be dug up every year.

Everything in Moderation

Adding wood debris to the soil for its improvement requires a balance between the carbon load added to the soil in the form of woodchips, water and nitrogen added to the soil at the same time to help it rot. 

Add Nitrogen

These sources of nitrogen help woodchips to decompose and rot without affecting other plants growing in the same area. Without this additional nitrogen, plants growing in the area yellow and may die. Seeds planted in these types of amended soils fail to germinate.

            Additional nitrogen can be added by chopping up kitchen scraps, green waste from the yard such as leaves and grass clippings and even mixing in commercial fertilizers high in nitrogen such as 21-0-0. Rotting is sped up by turning it and keeping it moist.

More Leaf Drop in Apricot - Its Hot, Check Irrigation!

Q.  We have an apricot tree about 5 years old.  It’s always seemed happy but this year it leafed out beautifully then last week started losing it’s healthy green leaves on one side.  Apricots are on the tree, but not developed yet. Now half the branches on that one side are leafless.

A. I looked at the picture and it looks like a watering problem; not enough water getting to the upper limbs and causing drought and leaf drop. Drought occurs first on the hottest side, the sides facing the sun. If you remember, we had a hot spell just before the weather cooled off again.

See if the tree is still alive

            Go to your tree and bend the smallest branches to see if they are still supple. For most fruit trees, if this problem is temporary they will be supple and bend easily without breaking. If this is the case, expect the tree to produce more leaves and branches after a couple of weeks if it is given water.

            Following the KISS rationale, we can eliminate the less likely disease problems, a weed killer spray drifting toward the tree, fertilizer misapplications and the like.

            Now, the cause of the drought. Water shortage to these limbs could result from not enough water applied to the tree or in the right areas, or damage to the trunk or limbs by boring insects tunneling through the trunk and limbs and interrupting the flow of water. If sap is not seen on the trunk or branches or the bark is not peeling off, then we can also probably eliminate borers.

Q. When is the best time 

to check fruit trees for borers?

A. The day after it rains.

            Leaf browning and dropping from borer damage usually happens around June or July when it gets hot. But inspect the trunk and limbs anyway for signs of borers.

Water, Water Everywhere

            That leaves us with irrigation, which is the most likely reason particularly because of the unusual weather. A five-year old tree should be pretty big so its water needs are also large unless you have purposely kept it smaller through pruning. A five-year old tree probably needs around 25 to 30 gallons of water each time it is irrigated. This water should be applied to as much area under the canopy as possible.

How Many Emitters?

            The minimum number of emitters needed for a five-year old tree is four; each located about 12 to 18 inches from the trunk in a square pattern surrounding it. Six emitters arranged in a circle 18 inches from the trunk would be even better. Apply the water long enough so it penetrates to about 18 inches deep. I don’t know how many minutes this would be because each irrigation system is different. But keep the number of minutes the same as before and increase the size of the drip emitters instead if the water is not deep enough.

Giving the Tree the Shaft

            To judge if you applied enough water, use a long steel rod, like a three-foot length of rebar, and push it into the wet soil after an irrigation. Do this in about three or four locations to get an average irrigation depth.

            This time of year, water about Three times a week if the soil is covered in woodchips. A thick layer of mulch on top of the wet soil usually saves one or possibly two days between irrigations. In June, water three times a week when it starts to get hot. If you aren’t sure when to irrigate, use a soil moisture meter like those for houseplants, to measure if the soil is dry enough to water again. Don’t trust the surface of the soil to tell you. Push the tip in the soil about 4 to 6 inches deep to get a measurement.

Black Spots on Tomato and Lettuce

Q. I have six tomato plants grown from seed, all indeterminate. They were growing in two-year-old, rich soil mix containing compost that produced a lot of tomatoes last year. The leaves of the tomato plants developed okay but then they got spotty and dried up. No blossoms at all. The leafy vegetables grew well but the older leaves at the bottom of lettuce also developed black spots, became yellow and died.

This gardener has been growing tomatoes this gardener has been growing tomatoes for over 30 years in the Las Vegas Valley. He seems to favor Celebrity but he grows them in the same spot year after year. We've got to learn to rotate vegetables so they are not grown in the same spot year after year.

A. I looked at the pictures you sent. Tomato diseases are tough to diagnose with pictures but I think this might be bacterial leaf spot. I first got suspicious when you said you started these plants from seed. Then I considered the wet, cool weather, which is perfect for this disease to develop, and concluded it was probably bacterial leaf spot. 

Bacterial leaf spot in North Carolina

Tomato disorders from Iowa

Google some pictures of this disease on tomato and lettuce and see if you think it looks like the same and let me know. Leaf spot diseases such as bacterial leaf spot can occur on lettuce as well.

Google pictures of bacterial leaf Spot

            Leaf spot diseases can infect the plant from seed contaminated with this disease agent. Most seed will have this disease present so applying a hot water or chlorine seed disinfection helps reduce this disease possibility. Methods for doing this at home can be found on the Internet or I can forward instructions to you.

            Cool and wet weather, perfect weather for this disease, promotes bacterial leaf spot if it’s present. This disease can become a problem if the growing area has not been cleaned up and old fruit and fines are present. 

Also, don’t grow vegetables in the same location year after year (implement crop rotation) to reduce the possibility of this disease, and several others, from occurring. Crop rotation can be as simple as not growing the same vegetable in the same location in a raised bed year after year.

            Indeterminate tomatoes have vines that keep getting longer and longer while determinate tomatoes produce short vines and flower sooner. For earlier production of tomatoes, choose determinate tomatoes rather than indeterminate ones. 

Determinate tomatoes are better for most home gardens in the hot desert anyway because you want to produce tomatoes as quickly as possible. Hot weather can come quickly and air temperatures above 95F can stop tomatoes from forming from the flowers.

            If you select indeterminate tomatoes, and then fertilize them with high nitrogen fertilizers, the plants will grow beautifully but produce few flowers until they get older. When growing indeterminate tomatoes, don’t fertilize plants after planting until they begin to bear fruit.

Rotating Vegetable Crops to Prevent Diseases

By Robert Morris

Prepared for ACDI/VOCA on March 10, 2009

Rotating fields to different crops each year is one of the most important and easily implemented disease control strategies for farmers. This practice avoids the buildup of many plant diseases in the soil. The longer the rotation before coming back to the crop, the less likely a disease will occur. 

Because diseases usually attack members of the same plant family, it is best to avoid planting crops after each other that belong to the same family. Insect damage may increase when the same crop is planted in the same area over several years as well. Here are some common vegetables and the families they belong to.

• Tomato Family: Tomato, potato, eggplant, peppers
• Cucumber Family: Cucumber, melons, squash, pumpkin, gourd
• Lettuce Family: Lettuce, endive, salsify, Jerusalem artichoke
• Onion Family: Onion, garlic, leek, shallot, chive
• Carrot Family: Carrot, parsnip, parsley, celery
• Cabbage Family: Cabbage, broccoli, cauliflower, Brussels sprouts, kohlrabi, turnip, radish, Chinese cabbage, kale, collards, rhutabaga
• Beet Family: Beet, Swiss chard, spinach
• Pea Family: Peas, snap bean, lima bean, soybean
• Okra Family: Okra
• Corn Family: Sweet corn, field corn, wheat, barley, oats

Some choices of crop rotations include Pea Family to Corn Family, Lettuce Family to Cucumber Family, Cucumber Family to Cabbage Family, and Cucumber Family to Corn Family. Rotating beans with a grain crop such as barley, oats, rye, wheat, or field corn or with a forage crop is very beneficial for root-rot control. One or two years in a grain crop is often long enough to prevent severe root rot when the field is not heavily infested with this disease.

Some diseases that come from the soil are not easily controlled by rotation. Such diseases can live a long time in the soil and are not affected by rotation. Examples include clubroot that attacks the Cucumber Family, Phytophthora blight, and Fusarium wilt of several crops. Other diseases attack so many vegetables that they can survive indefinitely on many different plants including weeds. These diseases include Sclerotinia, Rhizoctonia, Verticillium and root-knot nematodes. 

Many diseases can survive successfully because they can live on plants and plant parts left in the field after harvest. However they are unable to survive once the plants left in the field decompose. Destruction of plants and parts of plants left in the field after harvest can eliminate this problem. Plowing the field after harvest and before letting the soil rest can reduce the amount of disease that will survive.

Rotate Plants to New Locations Regardless of Area

            A YouTube video of a home gardener caught my attention recently who said that crop rotation (putting vegetables in different spots each time you plant to reduce disease and insect problems) wasn’t important for home gardeners. He said it was meant for commercial growers.

https://www.youtube.com/watch?v=ki2Xc8s44sI

            I could not disagree more! Crop rotation has been around for over 150 years as a good management technique for reducing disease and fertilizer problems, whether you grow a small number of plants or large numbers. I have seen this technique violated by small-scale growers in other countries with total disease devastation to tomatoes, peppers and cucumbers.

Some vegetable families to keep in mind include:

• Tomato Family: Tomato, potato, eggplant, peppers
• Cucumber Family: Cucumber, melons, squash, pumpkin, gourd
• Lettuce Family: Lettuce, endive, salsify, Jerusalem artichoke
• Onion Family: Onion, garlic, leek, shallot, chive
• Carrot Family: Carrot, parsnip, parsley, celery
• Cabbage Family: Cabbage, broccoli, cauliflower, Brussels sprouts, kohlrabi, turnip, radish, Chinese cabbage, kale, collards, rhutabaga
• Beet Family: Beet, Swiss chard, spinach
• Pea Family: Peas, snap bean, lima bean, soybean
• Corn Family: Sweet corn, field corn, wheat, barley, oats

            This technique switches the growth of vegetables to new locations every 3 to 5 years. It’s best to understand the families that vegetables belong to but if you don’t, then always grow vegetables that produce root crops (carrots, beets) in spots that previously had vegetables from flowers (tomato, pepper, eggplant) and follow that by growing leafy vegetables (lettuce, spinach, chard).

            If you are using a single raised bed, then simply grow these vegetables in new locations in the raised bed so they aren’t grown in the same location. Don’t grow vegetables in the same location for 3 to 5 years.

            An alternative method is to loosen the soil, lightly water it and then cover it tightly with clear plastic for three or four hot days in full sun, letting it bake. This method, called soil solarization, controls several plant diseases inhabiting the soil, as well as many insect pests and weed seeds.
              In the Mojave Desert we see dry soil surface temperatures reach 170F routinely in the middle of summer. We need that temperature to about 8 inches deep so cultivate and water the soil before covering it in plastic.

             This YouTube gardener may have success now without using crop rotation but he will learn this lesson the hard way in future years. Let’s not “throw the baby out with the bathwater.” Probably the worst part is that this propaganda will circulate on YouTube for many years to come and will lead home gardeners down a very dangerous and uneducated horticultural path.

Uses of Gibberellic Acid

 I put this on my blog in response to a question I recently received

https://xtremehorticulture.blogspot.com/2015/07/gibberellic-acid-on-grapes-can-make.html

Uses of Gibberellic Acid

Robert L. Morris

March 10, 2009

Gibberellic acid (also called Gibberellin A3, GA, and (GA3) is a hormone found in plants. Gibberellic acid is a very potent hormone whose natural occurrence in plants controls their development. Gibberellic acid promotes growth and elongation of cells. It affects decomposition of plants and helps plants grow if used in small amounts, but eventually plants develop tolerance for it. Gibberellic acid stimulates the cells of germinating seeds. Since GA regulates growth, applications of very low concentrations can have a profound effect while too much will have the opposite effect. It is usually used in concentrations between 0.01-10mg/L.

Gibberellins have a number of effects on plant development including rapid stem and root growth and increase seed germination rate.

Gibberellins are used in agriculture for various purposes. GA-3 is sprayed on seedless grapes to increase grape size and yield, and it is used on navel oranges, lemons, blueberries, sweet and tart cherries, artichokes and other crops to decrease or increase fruit set, delay rind aging, etc. These effects are highly dependent on concentration and stage of plant growth. GA is used to trigger flowering of sweet potatoes in breeding programs, to help tomatoes set fruit at high temperatures in the tropics, overcomes the need for chilling or long days to trigger flowering, and so is used in the tropics for breeding.

Developing seeds are active sites of containing GA and studies have found increases in GA levels in seeds during germination. The germination of old seeds has been improved with use of GA. Applied GA-3 may trigger dormant seed germination, in many cases overcoming the need for special or prolonged dormancy-breaking conditions such as cold treatment, light, after-ripening, etc.

1. Overcoming dormancy. Treatment with high concentrations of GA is effective in overcoming dormancy and causing rapid germination of seed.

1. Premature flowering. If a plant is sufficiently developed, premature flowering may be induced by direct application of GA to young plants.

1. Increased fruit set. When there is difficulty with fruit set because of incomplete pollination, GA may be effectively used to increase fruit set. The resulting fruit maybe partially or entirely seedless. GA has increased the total yield in greenhouse tomato crops both as a result of increased fruit set and more rapid growth of the fruit.

1. Hybridizing. Pollination within self-incompatible clones and between closely related species may sometimes be forced by the application of GA and cytokinin to the blooms at the time of hand pollination.

1. Increased growth. GA applied near the terminal bud of trees may increase the rate of growth by stimulating more or less constant growth during the season.

1. Frost protection. Spraying fruit trees at full-blossom or when the blossoms begin to wither can offset the detrimental effects of frost.

1. Root formation. GA inhibits the formation of roots in cuttings.

Recipes

Concentration parts/million	GA mg	Water ml (cup)	Purpose
50	125	2400 (10 1/2)	Early flowering
200	125	600 (2 1/2)	Early flowering
800	125	160 (2/3)	Blossom set
2000	125	60 (1/4)	Seed germination
1% paste	125	5 ml (1 tsp.) lanolin	Growth promoter

Table 1. Preparation of bloom or sizing sprays of gibberellic acid for use on various table grape varieties

Gibberellic acid is sometimes used in laboratory and greenhouse settings to stimulate germination in seeds that would otherwise remain dormant. It is also widely used in the grape-growing industry as a hormone to induce the production of larger bundles and bigger grapes, especially Thompson seedless grapes. In the Okanagan and Creston Valleys of Canada it is used in the cherry industry as a growth regulator.

Effects of Gibberellic Acid

Although GA is not listed as a "poison", the following precautions should be observed: Flush with water any GA that may get into the eye. Avoid skin contact if possible. If skin contact is suspected, wash with soap and water. Do not re-enter an area after spraying until the GA spray is fully dry. Avoid ingestion of GA. The powder may be dissolved as specified below to give the desired concentration.

Thinning and Increasing the Size of Table Grapes

In varieties like Thompson Seedless, Flame Seedless, Perlette and a few other varieties (seedless grapes primarily) GA3 (gibberellic acid) is used for either thinning out the number of flowers which set fruit, a bloom thinning spray, or for increasing the size of the berries (referred to as a sizing spray which is applied about one week following bloom). 

In some varieties both a bloom spray and one or two sizing sprays are generally applied. Not all varieties respond to bloom sprays for thinning. These varieties may use a gibberellin spray only for increasing the size of the berry. Grapes which produce seeds are generally larger than seedless grapes because seeds produce natural gibberellins which increase the size of the berries.

One must be extremely careful when using GA3 on grapes. Each variety has a different tolerance level and one should not ‘experiment” or use more of the material than is recommended for any given variety.

The gibberellin produced for commercial use in grapes is manufactured by Abbott Laboratories, Merck, and Agtrol. It is produced in both a powder formulation and a liquid formulation. For most home owners, the 4% liquid formulation (containing 1.0 gram/fluid ounce of formulated product) is the easiest to use. Before applying gibberellin to your vines, refer to the gibberellin product label and the variety write-up for levels which each variety will tolerate. Do not exceed the recommended dosages. Higher than recommended levels can severely injure the plant. Do not apply gibberellic acid to grape varieties not listed on the product label.

The spraying guide put out by the companies for the use of 4% liquid on grapes refers to actual grams of gibberellic acid applied in the finished spray per acre. Conversion for only a few grapevines is often difficult; so, refer to Table I below in which the values have been converted to parts per million (ppm) in a one gallon water solution. One gallon of solution is enough to treat two mature grapevines.

The rate of gibberellin used increases as the season progresses. Bloom sprays are generally much lower than sizing sprays which are applied about one week later.

References

J. L. Hudson Seeds website. http://www.jlhudsonseeds.net/GibberellicAcid.htm

Norton, Maxwell. 2007. Presentation at the University of Nevada Cooperative Extension Orchard Workshop.

Riley, John M. Gibberellic Acid for Fruit Set and Seed Germination. 1987 CRFG Journal (vol. 19, pp. 10-12). And can be found at http://www.crfg.org/tidbits/gibberellic.html

Wikipedia. Gibberellic Acid. Found at http://en.wikipedia.org/wiki/Gibberellic_acid

Leaf Color in African Sumac Speaks Volumes

Differences in trees can be because of their genetics and how they were propagated in the nursery, differences in soil in very small areas and management.

Q. We had 3 African sumac trees planted in our backyard 1½ years ago. We treated them the same during this time but the tree the farthest away has large dark green, healthy leaves and the other 2 trees have lighter color leaves and they are curled. 

A. African sumac is propagated from seed so there is a lot of variation among trees. They also come in male and female trees so let’s remember that as well.

Seeing seed pods in African sumac is a good indicator the tree is female.

            Lighter leaf color can mean the trees are not getting enough nitrogen fertilizer, they are watered too frequently, or the soil does not drain water quickly enough. Because these trees were not planted by you, it’s not known if the soil where these trees are growing drains water similarly or not.

            Let’s tackle the fertilizer issue first. Apply a high nitrogen fertilizer in the basin of the trees just before an irrigation. Let the irrigation water transport this high nitrogen fertilizer to tree roots. If nitrogen fertilizer is the culprit, you should see a change in the leaf color before one week.

Moisture sensors like this inexpensive type used for houseplants can tell you the approximate time to water. Push the probe into loose soil in several places to get a rough idea when the soil is wet or dry.

            Inexpensive soil moisture meters, such as they use for house plants, can give you a rough approximation if the soil is wet or dry and when to irrigate again. Water these trees only when the soil is beginning to dry, never while the soil is still wet. If trees are watered too soon and the soil is still wet, leaves can discolor and become yellow rather than dark green. But the differences in leaf density between the trees indicate a difference in the amount of water they are receiving.

Leaf Drop on Apricot Reasons Why

Leaf drop on any tree can happen if the flow of water from roots to the top is interrupted.

Q. We have a five-year-old apricot tree. Previously, it’s always seemed happy but this year it leafed out beautifully, then it started dropping its leaves. Apricots are still on the tree but not developed yet. Then this week ½ of the branches on one side are leafless.

Another angle of the same tree.

A. Pictures were sent to me of this tree so let me explain what I saw. The apricot tree is 6 to 8 feet tall with a similar spread but leaning strongly toward the light but away from some taller shrubs on one side. Leaves are on the ground and have dropped from the side away from the light. The week it dropped its leaves was a hot week and then it got cool again.

Apricot sap dripping from limbs or the trunk can be a sign of borers particularly if you see it when it gets hot.

            Trees drop their leaves because they are not getting enough water. They also drop leaves if it’s too dark, but I think in this case it’s a water issue. A lack of water can be from not enough water applied to the soil under the tree, borer damage in the trunk or several large limbs or a disease problem.

Sap dripping from the trunk can indicate wet soils. Add lots of water and then hold off watering until the soil has begun drying.

            I’m going to rule out the disease possibility because it is highly unlikely in the desert. Borer damage is a possibility except the leaves are dropping at the wrong time of the year and from half the tree instead of a branch. Borers cause leaf drop during the heat of the summer, June or July, frequently affecting an isolated branch or two. So, let’s rule out borer damage.

Wood chip mulch applied several inches think is good for fruit trees planted in desert soils but keep the wood chips a foot from the trunk for the first few years to prevent collar rot. Collar rot on fruit trees looks alot like drought.

            It is possible this tree had gotten larger and was not getting enough water. Along with a shortage of water, the distribution was not over a large enough area under the canopy to satisfy its roots. As trees get larger, they require more water distributed to a larger area under the canopy.

            To test this idea, use an inexpensive sprinkler on the end of a hose, connected to a mechanical timer at the hose bib or faucet. Put the sprinkler about 2 feet from the trunk of the tree and turn on the mechanical timer for two hours so it wets the soil deeply in an area about 5 feet in diameter. Do the same thing to the other side of the tree. Do this twice a week for the next two weeks and let’s see if the tree responds.

            If I’m right, you will see new growth coming from the limbs that are bare and where there are leaves, you will see new growth. If this is the case, increase the number and size of the emitters. Place one drip emitter scattered about every 2 feet under the canopy of the tree. The water should penetrate the soil about 18 inches deep after an irrigation.

Magnolias Need Special Locations and Management

Q. I have two dwarf magnolia trees in my courtyard in front of the house. They started dropping leaves and they’re kind of scarecrow looking. What do I do?

The Mojave Desert is not the easiest place to grow magnolias. Magnolias, Southern Magnolias in particular, will have difficulty growing in a desert climate.

A. Let’s get something out of the way early. This is not magnolia country so they will require extra care and attention here. I hate to sound like a broken record, but it is either water or soil improvement or both.

            Is it planted in rock? That’s a mistake if they are. These are not desert plants so they will not like rock. The soil around them should be covered with a 4-inch layer of woodchips instead.

Find the perfect spot, like planted in a lawn, and they may flourish for a few years. But don't plant them in a desert landscape.

            How many emitters do they have? They will need at least four if they are four or five feet tall. These will be placed in a square pattern about 18 inches from the trunk. This will be enough until they get about 10 feet tall and then you will probably have to bump it up to about six or eight emitters spaced evenly under the tree canopy.

            Making sure these trees get more water will stimulate more leaf development and a denser canopy. The water should be on long enough for it to drain to about 18-24 inches deep after each watering. Use a steel rod like a 3-foot long rebar to judge the depth of irrigation.

Asparagus Planting Among Trees

Q. I put in a lot of effort into planting asparagus. I have a large planted area but no asparagus! I planted Mary Washington this year and many times in the past, but I have had no luck. Are the trees nearby this area competing with them too much?   

Asparagus trials in 2008. About 15 varieties of asparagus were trialed in the Mojave Desert and evaluated by chefs for quality. All 15 performed well but those bred for the hot desert could be harvested for a longer period of time.

A. There is a lot to cover regarding asparagus growing here. First, there is no problem planting asparagus among trees if there is room. I will post a primer on growing asparagus in the Mojave Desert in here.

Make Sure There is Room for It

Asparagus gets 5 feet tall after harvesting the spears so make sure it has room to grow to that height. I have had asparagus planted among fruit trees, as well as alone in rows, since 1996. I planted asparagus in 2019 and they are coming up nicely. This is a great climate for asparagus if it’s planted and managed correctly.

Sometimes you will see advice to "snap" the spears off instead of cutting them. I tired it and don't like it. The remaining stubs above ground interferes with operations. I prefer to cut them about one inch below ground with a sharp knife or asparagus knife.

Just make sure the asparagus gets at least 8 hours of sunlight.

Variety Trials

            I have grown about 15 varieties of asparagus for comparison purposes in our Mojave Desert climate. They have all done well but there are some differences among the varieties. Stay away from heirloom varieties such as Mary Washington because they don’t produce enough spears in any climate. There is nothing remarkable about them.

I trialed a purple variety called Purple Passion years back and liked it. The spears were sweeter but the variety didnt produce as many spears as UC157. Choose improved varieties over the old standbys like Mary Washington. I prefer the UC varieties over Rutgers Jersey line.

            Expect an asparagus bed to last about 20 – 25 years if managed correctly. They do well with drip irrigation. I would use drip tubing with emitters spaced about 12 inches apart or plant them in containers for small spaces. In rows using drip tubing, plant in a triangular pattern so that crowns are 12 to 18 inches apart on either side.

Asparagus grows well with drip irrigation. Make sure you find a balance between soil moisture and drainage. If the soil is too wet, the roots will rot. If the soil is too dry, they don't produce well.

Asparagus Loves Manure or Compost Applications

            Asparagus loves rich soil and water but they also like their roots and crowns to “breathe”. Mix with desert soil an equal volume of rich compost at the time of planting about 12 inches deep. Buy two or three-year-old, all-male crowns and plant them 8 to 10 inches deep. Make sure the soil in the asparagus bed is free of any rocks or they will produce crooked spears.

Asparagus spear emergence in early spring after a rich compost application.

Asparagus Must Have Water Drainage

            The soil must drain water easily in a few hours after an irrigation. Irrigate thoroughly after planting but don’t irrigate again until the soil is slightly moist at 6 inches deep. If you’re not sure about when and how much to irrigate, follow my blog, Xtremehorticulture of the Desert, my YouTube video or podcast on how to irrigate. If watered too often, asparagus roots and crowns will suffocate and rot.

Differences in Varieties

            Plant ‘UC 157’ developed by the University of California for the hot desert and plant them from mid-January to early February. Stay away from planting by seed unless you are an experienced gardener. If you want some variation in spear colors, mix in a variety called ‘Purple Passion’ but keep in mind they don’t produce as many spears as UC 157, but they are sweeter to the taste.

Abnormalities do occur like fasciation but they are rare.

Don't Forget to Fertilize

            Each year, before the beginning of the growing season just after the Christmas holidays, apply about 1 inch of rich compost on top of the soil above the crowns and water it in. If the soil has plenty of organics in it already, then use a mineral fertilizer such as 16 – 16 – 16 in early spring.