Issue: April 1, 2000

Hardiness zones

I was hoping you could tell me what zone I live in or what I should be looking for when attempting to put together a landscape plan for my new house. I am confused. I live in Corrales, which is just outside of Albuquerque, about 1 miles west of the Rio Grande.

According to the USDA hardiness zone map, you should consider your location in Corrales to be hardiness zone 7a; that is, you should expect to be able to grow plants which can survive temperatures of 0 to 5 degrees Fahrenheit.

In New Mexico however, mid-winter minimum temperatures are not the only factor we must consider. We should also consider how early the plants tend to break dormancy and how rapidly they enter dormancy in the autumn. It is spring and fall that often injures our plants. In the spring, temperatures fluctuate between relatively high temperatures and very cold temperatures. In the autumn, we occasionally have a prolonged warm period followed immediately by extremely low temperatures that can kill or injure our landscape plants. Plants which should be hardy to low temperatures in the winter are often injured if they experience these same temperatures in fall or spring.

You mentioned that you were confused, perhaps by the topic discussed above, but I have noticed many people who are confused by the fact that there are other hardiness maps. Sunset magazine publishes a map that is very different from the map that is published by the USDA. If you see the Sunset magazine designations and compare them to the information in most garden catalogs, you will certainly be confused because most nursery catalogs use the USDA hardiness zone map.

Microclimates are variations in climate over small geographic areas, such as your own landscape. Microclimates will create areas in your climate where temperatures are warmer or colder in some places than in others. The landscape on the south side of a home is considerably warmer than that on the north side. However, the choice of which side on which to plant is not straight forward. The fact that plants stay dormant longer on the north side may make it a preferred location even though it is colder. For example, if the plants can withstand the cold on the north side and would otherwise begin growth too early, then the north side would be preferred. In the warmer climates you may grow plants which are not expected to be hardy in your area.

To avoid confusion, be certain which hardiness zone system you are using USDA, Sunset magazine, or any of the many others. You can also contact the Cooperative Extension Service and associated Master Gardeners in your county for information specific to your location.

Bulb flowers faded

My daffodils and tulips have finished blooming and the flowers have wilted. Can I cut their leaves back now?

The leaves are now creating food to restore the food reserves used by the bulb to produce the flowers. If you remove the leaves now, you will limit the recovery of the bulbs and therefore their ability to produce flowers next year.

Now is a good time to fertilize them and to be sure that they receive adequate water. In a couple of months they will begin to turn yellow and die. At the time the leaves begin to die, they have completed their work and may be removed.

You may wish to carefully plant annual flowering plants between the clumps of leaves of the bulb plants. The leaves of the daffodils and tulips will shelter the tender summer annuals from the wind and surplus sunlight which characterize New Mexico in the spring. In this way, the leaves of the daffodils and tulips will shelter the annuals while these annuals become established. The annuals will have time grow so that the ground does not appear bare once the daffodil leaves are removed.

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!