‘Drop-crotching’ a better method of pruning acacia trees

A: You can reduce the height of this tree. There is a pruning technique to lower its height called “drop-crotching,” which is very different from topping. Topping is extremely damaging to trees while “drop-crotching” lowers the height of a tree while maintaining the tree’s form as much as possible.

Very large trees cannot be reduced in size to very small trees. There is a limit how much a tree can be reduced in size by drop-crotching. When lowering the size of very large trees dramatically, reduce their size over several years rather than doing it in one season.

When drop-crotching a tree, you need to find very specific spots to cut where the form of the tree is not totally destroyed.

You’d first identify the vertical branches providing the most height. Trace these vertical branches to lower, less vertical side branches. Remove the vertical branches just above the juncture with the side branches.

You would repeat this at all of the locations that contribute to its unwanted height. By pruning in this fashion, you will retain as much of the trees natural form as possible.

A guide to drop-crotching can be found http://pubs.ext.vt.edu/430/430-458/430-458.html

If drop-crotching is not acceptable then removal is the only other option.

Q: I was going through my garden notes and I found pictures I took a few months ago of my tomato plants. A few of them came up with real gnarly roots. I have never seen anything like it.

A: This is definitely damage to tomato roots from root knot nematode, judging from your photos. There is no good way to totally rid the soil of nematodes. In the past, soil fumigants were used regularly to knock these critters back. Soil fumigants are being eliminated from the pest control arsenal due to environmental concerns.

Your options are to move your growing area to a new location that is not infested, grow in raised beds or containers and use resistant varieties. There are vegetable varieties you can find that are more resistant to nematodes than others.

Find varieties that have a capital “N” after their name. This stands for “nematode resistant.” An example would be the tomato variety Better Boy VFN, which is resistant to verticillium and fusarium diseases as well as nematodes. There are many others.

Build up your organic matter content with lots of compost. Nematodes don’t like soils with high organic matter.

Be very careful of transferring soils contaminated with nematodes to new beds or containers. This includes transferring them by using contaminated gardening utensils. Make sure utensils are sanitized between locations.

It is possible for this pest to migrate from your existing soil to a new raised bed constructed on top of soil contaminated with nematodes. You might consider laying thick plastic underneath the raised bed. Make sure the plastic slopes slightly to drain water and make the bed at least 12 inches deep.

Q: I am new to gardening in the desert and am surprised at my success thus far. That is, until the whiteflies came. They showed up on the grapes and zucchini first, maybe in May or June. Unfortunately, I didn’t think they would become a problem. By August they had attacked everything! I pulled broccoli plants and found I needed a mask to keep from inhaling them. What can I do this season?

A: Whiteflies are a very tough to control once they get established in the numbers you are talking about. They are much easier to control if you’re diligent about controlling them when you first see them.

Females lay a couple of hundred eggs at a time and these become adults that can lay more eggs in about six weeks. This means you can have exponential growth in their numbers if they are left undisturbed in six weeks.

Whiteflies, like so many garden pests, do not show themselves but remain hidden. Unless you turn over leaves and look at their undersides, you won’t know they are there until you see plant damage. Signs of damage are yellowing and scorching of older leaves, sticky residue on upper leaf surfaces of lower leaves and ants.

Ants love the sticky residue that whiteflies and aphids produce. Ants climbing on plants in the garden or on fruit trees is a good sign you have a developing pest problem.

If you buy vegetable transplants, spray the undersides of the leaves and stems with insecticidal soap, neem or horticultural oil. Once the transplants have been placed in the garden and they have grown a little, remove their bottom leaves that are within a couple inches of the soil.

These bottom leaves are the perfect hiding and living quarters for many problem insects. They are close to the soil surface so they can’t be sprayed easily.

Stay away from conventional garden insecticides unless this pest really gets out of control. Whiteflies are resistant to many pesticides and these traditional pesticides knock out whitefly predators that help keep them under control.

Get yourself a decent compressed air garden sprayer such as Solo or Chapin and use soap and oil sprays in rotation with each other. Early in the season when it is still cool, check the undersides of the leaves and look for critters.

Weekly applications are probably enough during cool weather. When it starts to get warm, inspect the bottom sides of the leaves and spray twice a week. Make sure you spray the undersides of the leaves. That’s where these critters are.

Control ants that are getting into the garden. They are buddies with aphids and whiteflies. Ants come from a nest in the ground. Follow their entourage back to the hole in the ground and apply a bait they can carry back to the nest. These are very effective for ant control.

If you see bottom leaves that are starting to yellow, pinch or clip them off. If they are yellowing, they’re not contributing to the plant anymore. Look at the underside. There are probably critters feeding. Remove these leaves and remove pest problems.

Q: I’d like to continue fertilizing my rose bushes right through the spring since the past year’s bloom was not too impressive. Is there any advantage or harm with that strategy?

A: High-quality roses are typically fertilized about every six to eight weeks through the winter, spring and early summer in our climate. Fertilizer applications are usually stopped during the summer months when flowering is the worst and resumes about a week before good flowering resumes.

Fertilizer applications are made to support healthy, vigorous growth and flower production. The timing of these applications varies with the type of rose and variety as well as the microclimate.

Generally speaking, roses perform very well in our climate for about eight to nine months of the year. Microclimates that are warm and protected in the winter may support the flowering of roses through the entire winter. In these microclimates you would fertilize all winter long.

In cooler microclimates you may see an interruption in flowering during the winter but have a longer flowering period in spring and fall. Fertilizer applications would support roses during their flowering periods. Your observations are better than any calendar.

If you are fertilizing roses frequently, then use smaller amounts of fertilizer or use fertilizers that release nitrogen more slowly. Make sure that roses receive an annual application of iron that is applied just before new growth.

Many rosarians like to apply Epsom salts as part of their fertilizer regime for its magnesium. Other fertilizers like SulPoMag and some palm fertilizers also contain magnesium and may be an appropriate substitute if you can’t find Epsom salts.

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.