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September 15, 2012

1 -Roses sometimes sprout from below their graft union forcing you to cut away a very vigorous growth.

2 -If you prune lilacs in the fall, except to remove the seeds, you will remove next year's flowers.

Yard and Garden September 15, 2012

Q. #1

I have a rose bush that makes beautiful, fragrant red flowers. It has grown a new stem that is taller than the rest of the rose bush. It looks similar to the rest of the stems except it has not made flowers and it does not have thorns. What is happening?

C. W.

Albuquerque

A. #1

It sounds like your rose has grown a shoot from below the graft union. Most roses we purchase and plant are grafted onto a rootstock that helps the plant adapt to a wide range of soils and environmental conditions. These rootstock plants are different from the variety we grow for the flowers and we do not want them developing from below the graft union. ‘Dr. Huey’ is a common rootstock plant that has the appearance you described. It flowers once in the spring. Its flowers are pretty, dark red, and semi-double. However, once they have flowered, they do not produce flowers again until the next spring.

If you do not remove the rootstock sprout from the base of the plant, the new sprout will weaken the desired rose that produces the pretty red flowers you like. You can remove that shoot at any time you recognize that it has developed from below the graft union. To do so cut it below ground level. It may come back next year, so be vigilant and remove it as early as possible next year. Be sure you are not removing a new basal sprout from the desired variety. You will recognize it by the absence of prickles, commonly called thorns.

Growth from below the graft union will often develop after some injury to the desired variety due to winter cold. The winter of 2011 may be the culprit. However, if you prune your roses too early, a late frost may injure your plants resulting in development of these sprouts.

Q. #2

I did not prune my lilacs this spring after they bloomed. Is it too late to prune them now? I know that pruning in the winter will remove the flowers for next spring.

Alice S.

Socorro

A. #2

Yes, it is too late to prune the lilacs without removing at least some of the flowers for next spring. Those flowers form in late summer, so the buds for next year’s flowering are already present. It is best to prune the lilacs immediately after flowering in the spring. This directs energy into new growth instead of the seed capsules that form after flowering. If you have unsightly seed capsules on the plant now, it is OK to prune them off to improve the appearance of the plant, but the benefits of increased growth and flower production are already lost.

For more gardening information, visit the NMSU Extension publications Web site at http://aces.nmsu.edu/pubs/_h, or to read past articles of Yard and Garden go to http://aces.nmsu.edu/pubs/periodicals.html

Send your gardening questions to:

Yard and Garden, Attn: Dr. Curtis Smith
NMSU Agricultural Science Center
1036 Miller Rd.
SW, Los Lunas, NM 87031.

Curtis W. Smith, Ph.D., is an Extension Horticulture Specialist emeritus with New Mexico State University's Cooperative Extension Service. NMSU and the U.S. Department of Agriculture cooperating.