Issue: May 12, 2007

Houseplants benefit from summer outside

Question:

Now that the weather has warmed, I have moved my houseplants outside. I thought it was good for my houseplants to spend the summer outdoors, but when I do this the plants seem to suffer. What am I doing wrong?

Answer:

It is indeed good for most houseplants to spend the summer outside, but there are some plants that can't easily tolerate our outdoor conditions in New Mexico. These plants may need special conditions when moved outdoors.

Some plants, especially those from humid tropical climates, can' t tolerate our dry air and wind. They desiccate rapidly, even when their potting soil is kept moist. These plants will need a shady location protected from the wind.

Shade is important for many houseplants. Afternoon shade is especially beneficial. Some plants can tolerate full sunlight if they are first gradually exposed to brighter and brighter light. Some plants require at least 4 to 6 hours of direct sunlight each day, but they must also be gradually exposed to brighter light when first moved outside.

Other plants don't easily tolerate the accumulation of salt in the potting soil. These plants will benefit if watered with captured rainwater or use of distilled water to dilute the natural salts in tap water. Plants may not do well if given only distilled water, so by mixing it with tap water you can reduce the salt problem and avoid the expense of using large quantities of distilled water for houseplants. The amount to add to dilute the salts in tap water will depend on the quality of your tap water. Start with one part distilled to one part tap water or one part distilled water to three parts tap water. Remember that when you add fertilizer to the water, you are adding mineral salts.

If salts have accumulated in the potting soil during the winter, now is a good time to repot the plants. Remove them from the old pot, gently wash away some of the old soil. You don't have to wash all the old soil away. Then place the plant in a new, clean pot and replace the potting soil around the roots. Water well to settle the new potting soil. Add additional potting soil if the soil settles when watered.

For some plants, it is best to never let the potting soil dry completely (cacti and other succulents can tolerate more drying). It is easier to leach salts from the soil with the next watering if the soil has not dried completely. When watering, moisten the soil completely, and then add enough water to drain from the hole in the bottom of the flower pot. This will then carry surplus salts from the pot. If the soil dries between watering, water often drains around the dried soil and doesn't adequately moisten the potting soil or doesn't carry surplus salts out of the container.

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!