Watering houseplants can be a challenging
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Issue: October 11, 2008

Watering houseplants can be a challenging

Question:

I have recently taken my houseplants indoors and now I am having trouble keeping the soil moist. During the summer when the plants are outside, I water with the garden hose and never seem to have a problem. Now that the plants are indoors, I water until water runs out the holes in the bottom of the pot as I have read I should do, but the soil never seems to get wet. Some of my plants are wilting and others look normal. What can I do to water my plants?

Katie G.
Santa Fe

Answer:

Growing plants indoors is often a greater challenge than growing them outside. One of the reasons is that we must change our watering practices inside. Most people cannot use a garden hose indoors to spray smaller droplets of water over the plants and into the potting soil. Indoor watering requires more careful application of water which is usually applied in streams rather than by drops scattered across the surface of the potting soil. The scattered water drops (from the garden hose) moisten the whole surface of the potting soil, causing it to swell somewhat trapping water in the potting soil. Potting soils often shrink when they dry between irrigations. When water is applied in a single stream, the water often channels through cracks or between the soil and the pot rather than going through the soil and moistening it. The result is water coming out the bottom of the flower pot more quickly. The gardener then stops watering to avoid damaging furniture as water fills the dish under the flower pot. Following the usual directions, the gardener prevents water from soaking back up into the soil to prevent accumulation of salts. The end result is that the potting soil may not be uniformly moistened and the plants may not receive enough water.

There are things you can try to remedy this problem. First try watering before the soil dries enough to shrink away from the pot. Some plants must dry somewhat between irrigations, but others will appreciate the even moisture and lack of drying.

Another technique is to apply a little water over the surface to slowly moisten the, and then as it swells, apply more moisture until the soil has moistened throughout.

Finally, you can do what appears to break the rules, that is, to water from the bottom. Your goal will be to allow the soil to moisten from the bottom to the top. Place the pot with dried potting soil into a dishpan or other basin of water and allow water to slowly seep in from the bottom. Do not fill the basin so deeply with water that the flower pot floats and tips over. You may need to add water after the soil has absorbed some moisture and become heavier. Once the soil has moistened, it is important to remove the pot from the water and allow surplus water to drain from the soil. This drainage will carry away surplus salts. In fact, by moistening the soil well before draining, more salts will be flushed away than if you had watered from the top. So, you really are not breaking the rules that say you should not let the water be reabsorbed from the bottom after watering.

If you need to fertilize your houseplants, apply a diluted liquid fertilizer after moistening the soil as described by the methods above. Apply fertilizer to moist soil, not dry soil, even when using liquid fertilizers.

Send your gardening questions to:
Yard and Garden, ATTN: Dr. Curtis Smith
NMSU Cooperative Extension Service
9301 Indian School Road, NE, Suite 112
Albuquerque, NM 87112

Curtis W. Smith, Ph.D., is an Extension Horticulture Specialist with New Mexico State University's Cooperative Extension Service. New Mexico State University is an equal opportunity/affirmative action employer and educator.