Ugly globe willow

My globe willow trees used to be pretty. Now they are forming leaves, but I can tell that this will be another year in which there are many dead branches. It seems that each year more of the tree dies. During the summer the leaves turn yellow and the tree just doesn't look as healthy as in years past. What can I do?

The globe willow, while it can be a beautiful tree, has several liabilities. The first is that it is often a weak tree with a short life. While it grows rapidly, it also declines rapidly. It is subject to several insect and disease problems. It often suffers winter injury which may appear as twig and branch die-back or as patches of dead and peeling bark on the south or southwest side of the tree where it was injured by the winter sun thawing it each day while it re-froze each evening.

The globe willow does not tolerate the high salt levels, especially sodium salt, common in New Mexico soils. It needs more water than most other trees. While the tree is young, the smaller tree needs a lesser quantity of water, but as the tree becomes larger, it becomes difficult to provide adequate water. This is a tree which will perform best if planted in valley soils where it can be flood irrigated with good-quality, non-salty water or otherwise kept well irrigated.

Even when it receives excellent care, it is subject to winter damage. This then predisposes the tree to insect and disease attack.

What should you do? If the tree is still in reasonable health, increased irrigation over a large area (extending to a distance from the trunk equal to the height of the tree) may help. If sufficient damage has been done by winter stress and insects and diseases, increased irrigation may not be able to help the tree. Another solution is to plant another, tougher, better-adapted tree nearby. Chinese pistache, any of several oaks, or ash trees could be planted to provide a longer-lived tree. If you live in a valley location, a native cottonwood, not a hybrid poplar, may also be a good choice. If a smaller tree would be appropriate, there are several flowering and fruiting trees to consider. Contact your local County Extension office or favorite nursery for other suggestions.

Fewer bugs?

I have noticed fewer aphids on my roses and irises this year. What happened?

We finally had a relatively cold winter which killed insects, at least some insects in some parts of New Mexico. This does not mean that we will have no insect problems this year, but in some areas it is delaying the annual explosion of some pests.

The absence of the pest species means we may be able to delay control measures, but it also means a delay in the appearance of the natural predators and parasitoids that prey on the pests. Without the presence of the pest, there is no food for these insect "good guys."

Continue monitoring the condition of your garden plants. In time, some pest species are likely to appear. Also watch for signs that the beneficial species are present. By being vigilant, you will be prepared to apply appropriate control measures if and when they are needed.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!