Pecan trees grow well in desert but consume considerable water

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 that you really have to think twice about growing them 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 4 pounds of this fertilizer for every inch of trunk diameter at chest height. If it is 20-20-20, use 2 pounds; 16-16-16, use 3 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.

Q: We have a 9-year-old chitalpa tree that has deeply cracked bark. The tree is in the front yard of our south-facing home and provides shade. Is there anything we can do to save it?

A: This tree easily gets sun damage, sunscald, on the trunk on the west and south sides if the trunk is fully exposed to the sun. Sunscald causes deep cracks in the trunk as the trunk dies on that side and begins drying.

The trunk is dead on this side and, as the trunk dries out, it cracks. It is not dead on the north and east sides, and this may be enough to keep the tree alive. It is possible for the tree to recover from this type of damage.

Not much you can do about the damage already done. When growing this tree, it is best to leave lower limbs to help shade the trunk until it gets older. At this point, all you can do is make sure it has enough water and fertilize it in the spring to help it recover.

Fertilize once a year with something like 16-16-16 in late January or early February. This helps push new growth which shades the trunk.

If there is new growth coming from the trunk, don’t remove it. Remove it when this new growth gets larger than pencil diameter. Otherwise, leave it alone.

Q: What causes leaves to yellow and black spots to develop on leaves of my calamondin citrus tree? I had them for seven years and they just now developed these problems. Nursery information desk advised picking off all affected leaves (but there are too many) then spray with copper fungicide.

A: Combined with leaf yellowing, it sounds like either a nutrient or watering problem or both, not a disease problem. Copper sprays are usually recommended for disease control.

If these citrus trees are in rock mulch, then it’s a nutrient and drainage problem. Auger four or five holes into the ground, 2 feet deep and 1 to 2 feet from the trunk, to improve drainage. Fill these holes with soil mixed 50/50 with compost and an iron fertilizer.

Mix iron chelate with the compost before using it to fill the augured holes. Water once a week through the augured holes, filling them with a hose.

Also, try spraying the leaves with an iron chelate solution four or five times, a few days apart. If this is an iron problem, even though it’s caused by poor drainage, the leaves should begin to get darker in color.

Nutrient problems can be caused by poor drainage. That’s why I’m giving a recommendation to improve the drainage using vertically augured holes and combining it with a compost and iron application at the same time.

Q: I’d like to trim my hawthorns because they are too tall. If I do that now in October, will I be removing the blooms that emerge in the spring?

A: The general rule of thumb is if a plant blooms in early spring (January, February, March and even April), then its flower buds developed during the previous late summer and fall months. Pruning with a hedge shears, or cutting off all the new growth with a hand shears, removes flower buds as well as the spring flower show. Think photinia and pyracantha.

If it blooms during the summer, then it produces flowers on its new growth. In this case, winter pruning will not remove the flower show. But summer pruning does. Think oleander.

The key to whether you get a spring flower show is really more about how the pruning is done. Trees or shrubs that bloom in the early spring, if pruned correctly during the winter, will still provide a flower show.

Pruning with a hedge shears, unless the plant is part of a hedge, is never the right way to prune. When pruning shrubs, choose between two different techniques: renewal pruning or rejuvenation pruning.

Renewal pruning is what is done to lantana. It is cut to the ground, leaving 1 or 2 inches sticking above the soil to provide for new growth. This type of pruning is done to overgrown, woody oleanders and many other overgrown shrubs.

Rejuvenation pruning is selectively cutting two to four of the older stems, close to the ground, every three to four years. This is done to plants that don’t grow back as quickly as lantana or oleander.

Rejuvenation pruning selectively removes a few of the oldest stems to make way for younger growth which grows from the base. This pruning technique always leaves a floral display, regardless of the plant and when it blooms.

Prune hawthorns now, and you will not interfere with the spring floral display if you use rejuvenation pruning. Pick three to four of your tallest stems and prune them back to within a few inches of the ground.

Q: I would like to plant some bee attracting plants this fall. I read that bee balm is excellent but that Vegas is not the best climate for it. Do you have some suggestions for plants in Las Vegas?

A: Bee balm, Monarda, will grow fine here. It just isn’t a desert plant, so don’t treat it like one. Bee balm cannot be planted and cared for as you would, for instance, desert marigold, a true desert plant.

Bee balm will need soil improvement at the time of planting, and it needs to be watered more often than plants such as desert marigold. Many herbs, such as rosemary, are great for attracting honeybees. Other herbs favored by honeybees include oregano and marjoram.

During hot weather, honeybees like scavenging for water. They are constantly hauling water back to their hives to help keep it cool. If you have lots of plants flowering in the yard, then providing water that honeybees can haul may be a partial solution.

Provide a shallow reservoir of water with a “landing area” so they won’t drown. Make sure the water is changed regularly so that it’s clean, like a birdbath.

Bob Morris is a horticulture expert living in Las Vegas and professor emeritus for the University of Nevada. Visit his blog at xtremehorticulture.blogspot.com. Send questions to Extremehort@aol.com.