In the garden

— Janet Carson is an extension horticulturist with the University of Arkansas Division of Agriculture. Write to her at P.O. Box 391, Little Rock, Ark. 72203, or e-mail her at

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QI was interested in one of your recent columns regarding when to severely prune holly shrubs.

Is the pruning schedule you mentionjust for holly shrubs, or does this also apply to other plants in the garden, such as nandina or gardenia? Is there a reference book you recommend that contains ideal pruning schedules for various plants that grow well in the zone covering Hot Springs Village?

AWe do have some extension publications on pruning that could be helpful. The main questions you wantto ask when it comes to pruning are: When does it flower, how does it grow, and why do I need to prune? In the case of evergreen shrubs that are grown more for foliage than flowering, early spring is great. If you have spring bloomers, prune after they flower. Summer flowering shrubs are typically pruned before newgrowth begins.

Gardenias and big leaf hydrangeas are the exception, as they bloom in the summer but set flower buds in the fall. If pruning is needed, it needs to be done after the first flush of flowers in the summer.

For nandinas, I think they are at their prettiest in the fall and winter, so I would prune in the spring as growth resumes. Since they are cane-producing plants, we typically do rejuvenation pruning and thin out up to one-third of the canes at the soil line.

QWe have a problem with web worms in our pecan tree. It seems that in the last few weeks they have spread to other trees in our yard as well.

What is the cure for them?

AFortunately, fall webworms look worse than they are. The damage is usually more superficial. If you can reach the webs, pull them downand destroy them, or tear the web to allow other predators in. In Arkansas, there are typically three or four generations per year, and if you can catch them at the onset in May and June, it is easier to deal with, versus this late in the season.

QWhat is the best way to decrease the size of pampas grass? When should it be done? We have four large clumps that are probably 25 years old. Once long ago they were burned in the winter and came back well.

AAll ornamental grasses should be cut back annually before new growth begins in the spring. While burning is a practice that can be used, timing and control are critical, and you must live in an area where burning is permitted. When cutting grasses, cut them as close to the ground as you can.

With large pampas grass, that is usually no closer than 12 to 24 inches from the ground. If you don't remove the old growth, over time the old foliage will decay in the center of the plant and lead to the death of the crown.

Ornamental grasses are at their prettiest in fall and winter, so don't cut them too early.

QWhen I put my tropical hibiscus in my greenhouse for the winter, do I trim them back then, or do I wait until I move them back out in the spring? In general, when overwintering plants in agreenhouse, when should they be cut back?

ASince you have a greenhouse, pruning them back is not as much of an issue as it would be if they were moved into a heated home. If we are moving plants inside the house for the winter, we try not to prune them back, because some natural dieback is going to occur because of poor light conditions, low to no humidity and static temperatures inside during the winter. In a greenhouse, space may be more of an issue, since there should be ample light and humidity to keep them growing.

Most tropical flowering plants benefit from annual pruning to encourage more blooming the next season, since they usually bloom on new growth. You can do it now or early next spring before you move them outdoors.

QMy hydrangeas did not do well this year. They had black stuff on the leaves and what looked like insect holes. Should I cut them back or do they need a spray?

AMany hydrangeas looked bedraggled this year. We had so much rain and cooler weather that leaf spots were rampant. Rake up the spent foliage this fall and see how they look when they leaf out next year. No pruning or spraying this late. Pruning would actually hurt their flowering potential next summer, since flower buds are now set.

HomeStyle, Pages 39, 41 on 09/26/2009

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