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Published February 24, 2008, 12:00 AM

Ag Matters column: Transplant cramped houseplants now

If you have looked at your houseplants within the last week or two, you probably have noticed some new growth at the ends of the branches or shoots.

By: by Jim Stordahl, DL-Online

If you have looked at your houseplants within the last week or two, you probably have noticed some new growth at the ends of the branches or shoots.

As the sun moves higher into the sky and the day length increases, houseplants will begin to put forth some new growth and can be moved to larger pots. One greenhouse grower is reported to say that Feb. 11 is the day when houseplants in the greenhouse start showing new growth.

So, if some of your houseplants are growing in cramped conditions, now would be a good time to move them to larger pots.

There are several factors that indicate if a plant is pot-bound. First of all, if the plant requires watering once every 24 hours even during periods of cool temperatures, we can assume that it needs repotting.

Roots growing through the drainage holes of the pot are a sign that it is filled with roots. If you suspect that a plant may be pot-bound, tap it out of the pot to examine the soil ball. If it stands alone or has roots circling around the edge of the pot, the plant needs repotting.

If a plant is not growing or blooming well but is not pot-bound, look for other factors such as light, watering or temperature. In these cases, repotting will probably not correct the problem. There are some plants, amaryllis and Christmas cactus for example, that thrive when pot-bound.

When transplanting, select a container that is only an inch or two larger than the one you are moving the plant from. The temptation is to transplant the plant into a container that is considerably larger so that you will not have to transplant again soon. But, the plant will appear out of proportion in the pot and the likelihood of over watering will be greater.

Be sure the pot has provisions for drainage. If you are using a container without drainage holes, consider double potting the plant by first planting it into a plastic or clay pot with drainage holes and then placing it inside a decorative container.

To prevent soil from washing out the drainage holes, cover the holes with irregularly shaped pebbles, pieces of broken clay pot, or paper coffee filters. Do not, however, add a layer of clay pot shard or pebbles because they may actually slow the movement of water through the pot.

Avoid using garden soil in pots for houseplants as it does not drain well and may carry with it disease and pest problems. If you have only a few plants to transplant, purchase a good quality potting mixture.

There are many soil-less potting mixtures available that work well, although they may require more frequent watering and demand regular application of a houseplant fertilizer. Do not use peat moss alone as a potting medium as it is too lightweight to properly anchor the plant and does not drain well, making it easy to over water the plant.

If you wish to make your own soil based mixture, use two parts garden loam, two parts organic matter such as peat moss or well decomposed compost, and one part sand or perlite for drainage. It is important that the garden soil used in the mixture is pasteurized to prevent weed seeds from germinating as well as to destroy any fungus diseases that the soil may harbor.

When transplanting, put enough fresh moist potting mixture in the bottom of the container so that you can position the plant at the same depth it was in the old pot. After removing the plant from the old pot, carefully roll the old surface soil off the root ball using the heel of your hand. Inspect the root ball and remove any broken or rotted roots and those excess roots that may have been encircling the bottom of the pot. Gently loosen compacted roots around the edge of the root ball.

After the root ball is prepared, place the plant in the new container on the layer of potting mixture you have provided. Carefully firm more potting mixture around the edges to fill the space between the root ball and the container wall. Newly potted plants should be watered immediately to settle the potting mixture and to eliminate any air pockets that may occur.

Add a little more potting mixture if necessary after settling has occurred. Do not expose the plant to direct sunlight for a period of two or three days.

A general rule to follow is to fertilize every two weeks from March through September with a water soluble fertilizer at one-half the label rate. Houseplants should be fertilized only when they are actively growing, so they should not be fertilized during the winter months when they are semi-dormant.

An exception would be houseplants grown under artificial lights, which may need fertilization year around. If a soil-based potting mixture was used, the plant should not need fertilizing for 3 to 4 months.

If you’d like more great gardening information, please join the Clearwater Master Gardeners for their annual Spring Wake-Up Conference on March 1 at the Bagley High School.

For more information, call the Clearwater County Extension office at 800-866-3125. If email is your thing, contact me at stordahl@umn.edu.

This article was provided by Carol Hoffman, Stearns County Extension Service.

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