Late Fall Fertilization Requires Proper Timing and Plant Selection

Q. I have heard you mention applying fertilizer to trees and shrubs in the fall rather than the spring. Is now the right time to do that?

A. The concept is called “late fall fertilization”. I have mentioned it before. It first came to light in the management of lawn grasses. It was found the “effects” from applied nitrogen fertilizers in late fall could be stored over the winter. In the spring, these effects would “kick in” and get the lawn off to an early start without fertilizer applied in the spring.

            This concept was applied to landscape plants. The same seems to hold true. If high nitrogen fertilizers are applied late in the fall the effects from nitrogen fertilizers can be delayed until the following spring. This must be done after growth has stopped in the fall but before leaf drop or even change in leaf color. This concept can be applied fruit trees as well.

Too late for fall fertilization

            Outside of being a novelty, why would this be considered? Why not just apply the fertilizers in the spring? The primary reason, commercially, is labor. Frequently, springtime is a very labor-intensive time of the year for professionals. Late fall months, before pruning begins, is usually a slow time of the year. Taking a spring operation and moving it to the fall redistributes labor. Saves money for landscape companies. Maybe it is a better time for homeowners who do it themselves. Nice cocktail talk. Bragging rights.

The lawn on the right was fertilized in the late fall. The one on the left was not. In Salt Lake City, Utah. Bluegrass mix.

            Timing is critical. Time late fall fertilization to a time when growth has stopped or nearly stopped but before leaves have begun losing their color. Plants should no longer be growing but the leaves should still pull water from the soil to distribute the fertilizer throughout the plant for storage. Avoid late fall fertilizing on winter tender plants that are woody such as citrus, bougainvillea and Cape honeysuckle.

Cut Back Lantana After Leaf Drop

Q. You said trim Lantana in February.  Wouldn't it be OK to cut them back in December, or when they appear to be dormant?  

Lantana cut back in the winter by landscape company. It could be cut back more than this with no problems. See where it is growing from at the base? You could cut it back this much.

Lantana spring growth after cutting back in the winter

A.  Yes, any time after leaf drop. I give people a specific date so they can mark their calendar and get it done. Those of you more involved in your landscape should understand the principles better so you can apply them just as you are doing.

Early Leaf Drop Can Be Dry Soil or Fertilizer

Q. My young fruit tree suddenly lost its leaves. This happened after I changed to the fall watering schedule. A couple of weeks ago I had tree service fertilize all my trees and shrubs including fruit trees.  They said there is nothing in their mixture that could have caused this.

A. Trees and shrubs are normally fertilized in early spring, not in the fall. There is nothing wrong with fall fertilization but it should never be done in the fall to plants that are sensitive to freezing temperatures.

            When fertilizing in the fall, it is best to wait until all growth has stopped with only a few weeks remaining before the leaves change color. The month of November is usually a good time to do this.

            There are typically two reasons for sudden leaf drop if temperatures are still warm; soils are overly dry or improper fertilizer application. I agree with your tree company. There is nothing in their fertilizer mix that would cause leaves to drop BUT if fertilizer is applied incorrectly, or the soil is dry when it is applied, then the tree might experience unexpected rapid leaf drop.

Desert Dawn nectarine leaf drop after drought

            If the soil dries out too much, leaf drop should be gradual in the fall. Leaves wilt, they turn gray because they are drying out and they fall from the tree in about a week’ s time. If fertilizer is applied too close to the tree’s trunk or applied when the soil is dry, leaf drop would be sudden; “overnight”. Always fertilize when soils are wet and at least 2 to 3 feet from the trunk.

            Regardless, I don’t believe the tree has any long-term damage. To be sure, bend small branches from where the leaves dropped. They should bend easily without breaking. Supple branches after unexpected leaf drop in late summer or early fall is a good indicator. This means they will most likely come back.

            The worst time for unexpected leaf drop is in the spring during periods of active growth. Leaf buds for the following year have not yet been initiated. In the fall, when the tree has stopped growing but already formed leaf buds for next year, it would grow new leaves in a couple of weeks if temperatures are warm and the soil moist.

What to do?

            Irrigate the soil above the tree roots with a hose, flooding the areas where fertilizer was applied. Apply 15 to 20 gallons of water slowly to these areas. Do it again in one week. New leaves will emerge in 10 days to two weeks. Enough leaf buds will remain unopened for next spring’s growth.

Germinating Seed in Cold Soils and Winter Protection

            Temperatures turned cold this past week in mid November. Historically, we still have about three or four more weeks of warm weather so it probably will get warm again soon. But if you plant vegetables from seed, these cold soil temperatures should still be warm enough to germinate radish, peas, beets, possibly carrots and turnips.

Fluff up the soil with compost. 

            Raised beds in full sun and “fluffed up” with compost have the best chance of germinating seed during cold weather. If the soil is compacted and difficult to dig, it will stay cold and germination of seed will be slow, difficult and maybe impossible.

Tomato germinating under plastic in January

            If soil temperatures are suspiciously cool, peg the surface of the planting area with clear plastic and cover the edges with soil. After one week, cut a slit in the plastic and plant directly in this warmer soil through the slit.

Use Frost Blankets

            Expect freezing temperatures sometime during the first three weeks of December. Watch for a cold front like we just had and get ready to throw a frost cover or light blanket over tender citrus trees if weather alerts are predicting a freeze. Frost covers or frost blankets are the best.

Floating row crop cover and frost blankets for winter protection of raised beds

What? No citrus fruit again?

          Most important is to keep cold wind from damaging the youngest shoots. Wrapping the tree with Christmas tree lights may help if the lights are not LEDs and if the tree is protected from the wind. If the tree is unprotected, it may not have any flowers or fruit this next year. If temperatures are unusually cold, the tree may not have fruit next year regardless of what you do. A lot depends on where you live in the Valley.

Fertilizing Pecans: When and With What?

Q. When do I feed a 50-year-old pecan tree growing in our front yard and with what?

A. Pecan trees do well in our climate. But they are such a large tree and require so much water you really have to think twice about growing them here in the desert.

            If your pecan tree has been doing well in the past, then don’t change much. However, fertilizing pecan trees can mean an increase in the production of nuts and prevent alternate bearing (producing nuts every other year).

            Fertilize in February. If there is grass under the tree, then use a shovel to apply the fertilizer beneath lawn roots but above tree roots. Fertilizer is applied in “slits” in the grass about 6 to 8 inches deep. Make these slits in two concentric rings around the trunk and a distance equal to the spread of it’s canopy.

            The fertilizer is applied in the slit, watered, and the wet slit closed by stepping on it. Water these slits thoroughly to prevent damaging the grass.

            If there is no grass, then apply fertilizer where water is applied and in a similar manner. Let the water move the fertilizer to the roots of the tree.

            Select a fertilizer with all three numbers the same such as 10-10-10 or 16-16-16 or 20-20-20. If using 10-10-10, then apply four pounds of this fertilizer for every inch of trunk diameter at chest height. If it is 20-20-20, use two pounds; 16-16-16, use three pounds.

            Look for leaf yellowing or leaf growth in bunches at the ends of branches. If you see either of these problems, apply iron or zinc as well as the fertilizer. If not, then don’t worry about it.

            Water deeply during the growing season to make sure you get strong growth and flower production. If there is a late freeze, the tree may not have much, if any, nuts. Both a male and female tree are needed. If there is no pollenizer tree nearby, you won’t see any nuts produced. 

Common and Dwarf Myrtle Make Excellent Landscape Plants in Las Vegas

Suggested by Andrea Meckley at Imn2plants@aol.com

Why in Las Vegas Fruitless Plums are NOT Fruitless and Have Borers

Q. Perhaps you can tell me why in Odessa, Texas, fruitless plum trees are actually fruitless and don’t fall easy prey to borers.

A.  Ornamental plums, we sometimes call purple leaf plums, are actually fruit bearing trees (fruit trees) that are sold for landscaping because of their showy flowers. They are from a group of fruit trees collectively called “cherry plums”. Actually, some cherry plums have purple foliage and some have green.

            Two popular purple varieties are ‘Thundercloud’ and ‘Atropurpurea’. Cherry plums require a pollenizer (another tree similar but distinctly different) to set fruit. If no pollenizer is nearby, then there is little to no fruit.

Purple leaf Plum flowering

            Some cherry plums will set a only few fruit by themselves but many more fruit if a pollenizer tree is closeby. If there is a pollenizer nearby, you might see a lot of fruit produced.

            Fruit set without a pollenizer can depend on the climate as well. Late frosts after flowering can cause any fruit that might set, to fail.

            The types of borers present vary with the climate and geographical location. Also, borers are transported inside nursery plants between states. This is one method they have for getting around…by truck!

A very good indication that this purple leaf Plum has borers working inside the trunk

            If a state like Nevada is dominated with nursery plants grown in California, these plants are much more likely to have pests common to California. If plants are bought from nurseries in Texas (Texas has a booming nursery industry) then the pests are more likely to be pests common to Texas.

            Borers are decomposers. They are attracted to plants that are weakened or damaged. Our intense sunlight is tough on plants and can weaken them. Our soils are poor and can lead to unhealthy plants as well. These all make a nice hunting ground for borers.

Can't Find Yellow Honeysuckle in the Nurseries

Q. I cannot find the white or yellow honeysuckle here that grew in West Texas, Odessa, and smells so wonderful. 

A. The primary reason you can’t find familiar plants here is because of marketing and sales of local nurseries and gardens centers. The temperatures and soils are similar enough between West Texas and southern Nevada where many plants grown there would work here.These are Texas native plants that have become mainstreamed in Texas nurseries. Start asking for them at your local nursery and they will probably bring them in.

            You also have Texas A and M University which is very involved with the Texas nursery industry and, through their Extension Service, is helping homeowners and local nurseries in providing a wider variety of plants that will work there.

            Odessa is a little colder and not quite as hot as Las Vegas and the soils are…believe it or not… Better than ours primarily because there is more organics in the soils and more rainfall. West Texas is considered semi-arid, a part of the High Plains, while Las Vegas is in the eastern Mojave Desert.