Issue: Augus1 4, 2001

Direct Sun Killing Plants

I recently landscaped my townhouse courtyard with pots of Pretoria Canna and Big Leaf Philodendrons. They were full, beautiful and blooming. I have no patio cover and the pots sit on Saltio tile because there is no dirt. I think the tile draws heat to the plants. I have sprayed them daily and watered them enough to keep moist. The leaves on the plants look burned, and the plants are not producing any new leaves. What do I need to do before I lose them completely? -Karron B. (via internet)

The plants that you described are from understory locations in the tropics; that is, they are adapted to shade and have a really tough time with direct sun, especially in the Southwest United States. The heat does complicate things but is not the primary problem. The leaves are just sunburning.

The solution is shade. Some trellises placed in five gallon buckets or large flower pots and positioned to shade the plants, especially from mid-day until late afternoon, will help. The trellises alone may make enough shade, but vines planted on them will help more. Be sure to choose vines adapted to full sunlight locations, or for immediate benefit use artificial plants on the trellises this year.

Continue to provide adequate water and moisten the tiles during the day as you have been doing. The damaged leaves will not recover, but the plants should produce new leaves if they are not too severely damaged.

Tomato Problems

I am hoping you can help me with a problem. I have just moved to the East Mountains from Illinois and need some help figuring out how to grow tomatoes here. I brought the tomato plants with me from Illinois, and they look like the healthiest plants I have ever grown. They are in tomato cages, and I have not pinched off side sprouts. In Illinois, by this time I should be having ripe tomatoes, but here there is not a single tomato set on the five plants, and very few blooms compared to what is normal. Can you give me a clue as to what is wrong and what I can do next year, if not this year, to rectify it? One person suggested that tomatoes won't set because it gets too cool in the nights here. I would greatly appreciate any help you can give me. -Kathy A. (East Bernalillo County)

There is probably more than one factor working here. First, our summer day temperatures kill the tomato pollen, so even when the plants are flowering, there is little to no fruit set. This is variety dependent - cherry tomatoes, saladette, and other smaller varieties usually set better at high temperatures and often have a crop set before high temperatures develop. The varieties that produce larger fruit have more difficulty.

Low night temperatures can reduce flower development. Your statement that these were the best plants you have ever grown indicates good growth and perhaps high nitrogen fertilization (from commercial fertilizer, manure, and some composts). Nitrogen coupled with low night temperatures may reduce flower development, and high day temperatures may prevent flower set.

Growing several different varieties (of different size tomatoes) gives you a better chance of having fruit set. Don't make the soil too rich, nitrogen is needed, but balance with phosphate fertilizer. Choose varieties that will produce a lot of leaves. (Temperatures will be warmer under the foliage at night and cooler in the day time).

Please join us on Southwest Yard & Garden, a weekly garden program made for gardeners in the Southwest, broadcast on KRWG-Las Cruces on Saturdays at 11:30 a.m., Tuesdays at 6:30 p.m. and Thursdays at 1:00 p.m.; KENW-Portales on Saturdays at 10:00 a.m.; and KNME-Albuquerque on Saturdays at 12:00 noon, and Fridays at 2:30 p.m.

Send gardening questions to Southwest Yard and Garden, Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu or at https://www.facebook.com/DesertBloomsNM/. Please include your county Extension Agent (aces.nmsu.edu/county) and your county of residence with your question!

For more gardening information, visit the NMSU Extension Horticulture page: desertblooms@nmsu.edu.

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, office: 505-865-7340, ext. 113.