Issue: January 13, 2001

• Pruning hibiscus in New Mexico
• Reasons for timing of pruning roses, grapes, and lilacs

Pruning hibiscus in New Mexico

Are outdoor hibiscus bushes supposed to be pruned on an annual basis? I would appreciate anything you can tell me in regard to the care of hibiscus. I got one for a gift in mid-May last year. I planted it, and it was beautiful and bloomed until late in the fall. Nancy Vehstedt Las Cruces

Hibiscus varieties that are commonly grown outside in most of New Mexicowill die-back to the ground every winter and should be pruned back before growth begins in the spring. You can do it now, or you can wait.

Since you are in Las Cruces, there is a chance that you have the tropical type of hibiscus seen in Hawaii and other tropical locations. This hibiscus may survive mild winters in New Mexico but will probably be frozen back to the ground or near the ground each winter. Wait until spring after new growth has begun to remove any dead or freeze-damaged branches and twigs.

When very cold weather threatens, you may be able to protect the base of the tropical hibiscus by putting bags of dry leaves around the base of the plant to insulate it. Once the cold weather has passed, you can remove this mulch. They may also be grown as potted plants in much of New Mexico. As potted shrubs, tropical hibiscus will need some pruning to keep their size manageable so that they may be moved indoors to a brightly lighted location in the winter or to a cool (near freezing to slightly below freezing) location where they may go dormant (leaves will fall) and survive the winter. If they are maintained dormant and cool through the winter, they will not need light until new growth begins in the spring. At that time, they will need a brightly lighted location until they can be moved outside after the chance of freezing has passed.

Reasons for timing of pruning roses, grapes, and lilacs

I know the dormant season is the right time to prune most things but have read that I shouldn't prune roses, grapes, and lilacs now. Why?

Roses and grapes may initiate growth too early and be damaged by freezing if they are pruned too early. Many people have pruned early and the roses have done well, but there are a lot of roses in New Mexico growing from only the root stock (once flowering each year) as a result of improper pruning timing. It is best to wait until about a month before the expected last frost to prune roses and grapes to reduce the risk.

Lilacs (as well as forsythia and other early spring blooming shrubs) produce their flower buds in the late summer. These buds will bloom as soon as growth begins in the spring unless we cut them off. Pruning during the dormant season removes the flower buds before blooming. New flower buds will not be produced until the following summer, so you will have a spring without flowers. It won't hurt the plant; it will only prevent flowering.

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!