Summer Planting

Question:

I’d like to fill in some gaps in my landscape with a mixture of adapted and native plants, but I’m afraid of planting when it’s so hot outside. Is it ok to plant now? If so, what can I do to increase their chances of surviving the heat?

- Callie P., Albuquerque

Answer:

Yes, now is a great time to plant. I had my entire yard professionally landscaped last July, and I worried about the timing too. I just counted, and all 38 trees, shrubs, and vines that were planted are still alive and doing very well a year later.

It makes sense to worry about the heat stressing your plants, especially when they’re newly planted. But lots of gardeners have great success planting throughout the summer. If you have plants in containers that are waiting to go in the ground, go ahead and plant them now.

The trick at any time of the year is keeping soil in the root zone from drying out, without staying waterlogged. To me, this means being diligent and checking twice a day in the first few days to be sure the soil is moist. If it’s wet, don’t water quite yet, but check again in 12 hours or so. Once you get the hang of it, you’ll figure out that maybe twice a day will be too much, but every three days might be too few.

Want to know what’s going to help a lot? I bet readers who know me can already guess what I’m about to recommend… MULCH! Those of you who have a thick layer (4+ inches) of woody mulch already know how much it helps hold soil moisture between irrigations, even in what might be considered to be poor soils.

You also need to be sure you’re watering deeply enough to reach all the roots and at least a little beyond. If you’re applying water on top of your mulch, like with a garden hose, be sure the water is getting through that mulch layer and soaking the ground underneath.

No fertilizers or root stimulators are recommended at the time of planting or for the first few years. In fact, adding fertilizer when plants are just getting established can be detrimental because the roots haven’t developed enough to be able to supply water to the whole canopy, even if they’re well-watered. It seems counterintuitive, but for many common landscape species, you want the above-ground portions of the plant to grow very slowly in the first months after planting. The best-case scenario is that the young plant uses most of the photosynthetic energy created in the leaves to push root growth. Forming a healthy root system is the key to long-term success.

For more tips on planting perennials and before and after photos of my own home landscape, check out the Desert Blooms blog version of this column and stay tuned for a new column I’m developing about why planting trees and shrubs too deep is such a big problem.

This landscape was installed in July 2019. The plants not only survived but thrived even though they were planted in the heat of the summer. Photo credit M. Thompson

These summer planting concerns are common. We think of spring as being the ideal time to plant, but fall can be even better, and any time is better than never. You may have heard this one before, but “The best time to plant a tree was 20 years ago. The second best time is now.”

I searched the Southwest Yard & Garden column archives and found the following in an article written by retired NMSU Extension Horticulture Specialist Dr. Curtis Smith in August 2008:

“Now is actually a great time for planting some plants... Many Southwestern U.S. native plants are genetically prepared to grow during monsoon conditions and will thrive if planted now.

The autumn is also a good time to plant. Container grown trees and shrubs can be planted well into the autumn. Irrigation will be necessary to establish the plants, but many of these plants exhibit good root growth in the fall. Autumn is also less windy than the spring and that helps with maintaining soil moisture, so consider the autumn as a good planting time. Of course, that is also the time to plant spring flowering bulbs, so while you are planting the trees and shrubs, add some bulbs for early spring excitement in your landscape…

Finally, spring will come again with its winds and unpredictable temperatures. Spring is a good time for planting many things. Do not let the vagarious spring weather prevent you from planting… Once again, maintaining moisture around the roots requires irrigation.

There are three good planting seasons here in New Mexico. Each has its own benefits and limitations. While you may not be able to plant every landscape plant in every season, many can be planted in any of the three seasons if the plants are available.

As you have noticed, I mentioned irrigation in each instance above. Water is critical for the establishment of plants in the landscape. However, water conservation is also critical. Planting during the monsoon season with its precipitation is one way to maximize plant establishment while conserving water. Organic mulches (bark, wood chips) applied at the base of establishing plants helps conserve moisture and greatly enhance root development (in any season).”

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.

Links:

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 page.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!