Damaged tree trunk may recover on its own

Q: I have a beautiful 10-foot-tall oak that has provided privacy with its wonderfully dense light green foliage. I enclosed a picture of a rapidly expanding bark rot-looking area that seems to be circling the trunk and moving upward at the same time. Can this be stopped or cured, or is it life-threatening to the tree?

A: From your picture, which I posted on my blog, this damaged area of the trunk near the ground seems to be on the mend. You can see the bark “rolling” in over the wound. Let the tree trunk heal on its own.

From the looks of the damage, this was a “traumatic” event and not a disease. After damage like this, the living layer of plant tissue around the damage forms a “compartment” that isolates the damage and heals over and around the wound. This reaction is normal to a healthy plant after an injury that is a one-time event and not getting worse.

At first, it looked like collar rot, a disease, that was developing but I don’t think so. Just to be on the safe side, pull any gravel or wood surface mulch away from the trunk a distance of 12 inches and keep the trunk as dry as possible. If there is irrigation water applied close to the trunk, move the water source 18 to 24 inches away from the trunk.

When you’re watering, avoid daily or every-other-day irrigations, which might keep the soil wet. Deliver the water the tree needs for several days all at once, not a little bit every day. Judging from the size of your tree this might be around 20 gallons at a time.

Trees of this size should receive water from drip emitters in at least four different locations under the tree canopy.

In winter, irrigate about once every seven to 10 days, possibly longer if you can determine that the soil still has moisture. In summertime, you might water once or twice a week if you have several inches of mulch laying on the soil surface.

Q: I’d like to plant roses or tree roses or possibly a shrub on my balcony in containers. They will get morning sun and afternoon shade. When should I plant them?

Can the pot rest directly on the plate or should there be a space between the pot and the plate? I want to make sure it drains properly and I don’t want the water staining my white balcony.

A: You have a lot of flexibility in this location because the plants are in container soil and receive late afternoon shade. The limitations would be the total hours of sunlight the plants receive and winter low temperatures.

Flowering or fruiting plants need at least six hours of very bright sunlight to thrive. The best times for planting are in February through April or May. Another great time is in the fall from late September to mid-November. The winter months are OK for winter-hardy plants, but plants don’t establish quickly when container soils are cold.

Roses and other flowering or fruiting plants will do well if they get at least six hours of direct sunlight. Weight is a problem on balconies, so use lightweight soil mixes that contain a large percentage of perlite or vermiculite. These types of soils need water frequently.

Because of weight, stay with containers no larger than 15 gallons. The water-catching plate underneath can be in direct contact with the container without problems. If you’re using tap water, then about 20 percent of the water that you apply should drain out the bottom of the container so salts flush and don’t accumulate.

You might also consider vegetables, herbs and smaller citrus such as kumquat or lime.

Q: I want to plant a crape myrtle tree. Will it survive in the northwest Las Vegas Valley? When is the best time to plant and how should it be done? How do you care for this tree so it still looks good in this climate and soils?

A: Crape myrtle does very well here if the hole is dug wide and the soil is amended with a good-quality compost at the time of planting. This tree is not a difficult tree to grow here, but it does require some extra care.

Crape myrtle does well in full sun but it should not be placed in a total desert landscape surrounded by cactuses and rock mulch. It performs best in wetter parts of the landscape in soils with a higher organic content, surrounded by other plants and the soil covered in wood mulch.

The three biggest issues you must address are modifying the soil enough at the time of planting, mulching the soil surface with wood mulch and using a fertilizer that prevents the yellowing of the plant’s leaves from iron chlorosis.

I wouldn’t trust landscapers to plant this tree without guidance and some quality control. This tree won’t do well in a few years if it’s planted in a cheap hole. The hole has to be dug just deep enough to accommodate the tree. But the hole needs to be dug wide. Make sure the planting hole is dug at least four times the diameter of its container or box.

The soil used when planting and filling the hole around the tree’s roots should have plenty of good compost mixed with it. An equal volume of good compost to native soil would be the right amount.

Fertilize once in the spring, around mid-February, with a fertilizer formulated for flowering woody plants, trees and shrubs. A rose or tomato fertilizer is an example and could be used as a substitute.

When you fertilize this tree in February, give it 2 to 3 ounces of EDDHA iron chelate to supplement the fertilizer. Apply it to the soil beneath the canopy and water it in.

If you want to give it a little extra attention and have it look even better, apply a foliar fertilizer three or four weeks after the leaves come out. Use a product like a Miracle-Gro or Peters that is designed to encourage flowering. Make sure this tree is watered as frequently as your other woody landscape plants and with the same water volume as plants of a similar size. Crape myrtle is nearly pest-free.

Q: I’ve been thinking about growing milkweed plants to help migrating monarch butterflies. Any thoughts?

A: I agree with you wholeheartedly about encouraging our local butterfly and moth populations. They add beauty and grace to our landscape, provide some pollination and act as a food supply for other critters.

To my knowledge, the monarch butterfly does not pass through Southern Nevada in its migration. I understand there are two migration routes: one with the Eastern population and the other with a Western population.

The Eastern population misses us completely in its migration to Mexico. The Western population is restricted for the most part by the Sierra Nevada.

Instead of focusing just on milkweeds, I think a diversity of plant material for attracting these insects might be important. I have posted some reading material on my blog about butterfly gardens, plants that attract butterflies and which butterflies are common to our area.

Reducing or eliminating pesticide use in the butterfly garden area would be wise. There are a number of pesticides that are harmful; two that I recommend frequently to organic gardeners, Bt and Spinosad, can kill butterflies.

Always apply pesticides, if they must be applied, at times when these creatures are not active. This means the very early morning hours. Many of our moths fly at night, so I would avoid applying pesticides at dusk if a major concern are night-flying moths.

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.