June 25, 2011

Yard and Garden - June 25, 2011


Many plants died or were severely damaged by the freeze earlier this year. We have cut back many things numerous times. However, I am curious about my rosemary. It is a good size plant and each year I find that I have to cut off some dead branches. This year it was a bit brutal. I probably cut away half of the bush. It looks a little nasty now. I have been watching the plants in the medians and see that a commercial landscape company has done nothing. So I am curious - Did I do the right thing? Will some of this come back? Or, should I just dig it up and replace it?

- Mary B.



Cutting back the dead (dry, brittle) branches of rosemary in the spring is good. As you mention, there are often branches that die back during the winter and need removal in the spring. Often there are branches with green leaves remaining. New growth can also develop at the base of the plant. If you are not seeing new growth on the existing stems or developing at the base of the plants, the whole plant may have died. Confirm that the branch is dead by scratching the stem to see if there is a healthy, bright green cambium layer just under the bark. If you find a bright green cambium layer, there is still a good chance for new growth to develop. If you find only brown or black tissue under the bark when you scratch, the plant is probably dead and replacement is the best option.

2 - Newly planted trees often exhibit some signs of stress the first year, especially if the spring is harsh


We bought and planted two flowering pear trees this spring. All went well the first couple of weeks, than we spotted very small black bugs in the flowering buds causing them to brown on the tips and not develop. Later we discovered the leaves had red & purplish spots on them. We took samples three times to two well-known nurseries and were told we had damage caused by the continuous high winds - which we understood and that we had aphids. So we agreed to wash the tree down with water several times during the week. Not much success, so we sprayed with insecticidal soap, yet the problems remains. We are hoping for an environmentally safe

- Bill & Helen H.

Albuquerque Northeast Heights


It is not unusual to see problems in a newly establishing tree during the first growing season, especially when we experienced a spring such as we experienced this year. Even though the trees did not have to deal with the cold winter, this spring has been alternating cold and warm, often windy, and extremely dry. All of these factors will create problems for new (and old trees - especially old trees recovering from the extreme cold experienced last winter). The wind is a likely culprit for causing brown or black edges on the leaves. Purple spots may be due to bruising as the leaves were blown against the stems and by the aphids. Aphids feeding on the flowers may have caused the damage you described. Even smaller insects (thrips) may also have caused the symptoms you described in the flowers. As the tree develops in subsequent years, this should not be such a problem.

The damage experienced by the leaves will remain as long as the leaves remain. Treatment will not undo the damage already experienced. Washing with water is a good, non-toxic method to limit damage due to the aphids. Insecticidal soap is also effective in managing aphids and other soft-bodied insects, but the soap can remove protective waxy coatings from the leaves resulting in drying of the leaves. As the weather has become hot, this is a very likely result of insecticidal soaps (and many other sprays).

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.


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