Re-potting your houseplants

By Dawn Pettinelli - UConn Home & Garden Education Center
Featured Article - posted Tue., Jan. 8, 2013
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- Contributed Photo

Still searching for a New Year’s resolution that will not be difficult to keep? Take a good look at your houseplant collection and upgrade your plants’ existing conditions. Most indoor plants are not too demanding in their cultural requirements, but they would most likely benefit from some TLC. Give your plants routine groomings by removing dead or sickly-looking leaves, wiping down dust-covered foliage, and trimming wayward growth. Water and fertilize on a regular basis. See that their light and humidity requirements are being met.

Occasionally, houseplants need re-potting. Ideally, plants should be re-potted just before periods of active growth, which makes late winter a great time to tackle this task. Most plants require re-potting every year or so. Even plants that prefer to be slightly pot-bound will appreciate having their growing medium refreshed. Signs that plants need re-potting include roots growing through drainage holes, plants requiring copious amounts of water on an almost daily basis, and sometimes roots forming a dense mat in the top layer of potting mix.

As a rule, plants should not be moved into pots more than 2 inches wider than the ones they are presently growing in. While it may be tempting to use a larger container, the increased amount of growing media relative to the root mass will hold too much water, leading to saturated soils and root rot.

Old-time gardeners were forced to prepare their own houseplant potting soils. We are fortunate to have available to us a variety of commercially prepared products. Today’s potting mixes typically do not contain outdoor garden soil. Instead, they are comprised primarily of organic materials with several relatively inert substances added to improve the physical and/or chemical properties of the media. For years, sphagnum peat moss was the organic material of choice. It is readily available, lightweight and retains moisture and nutrients. More recently, bark products have replaced some of the peat moss used in potting mixes. A by-product of the timber industry, bark chips are inexpensive and plentiful. Generally the bark is reduced to one half inch or so and composted. Both peat moss and bark products are acidic, so ground limestone is added to modify the pH. Sometimes coconut coir or composts are also used in potting mixes.

Perlite is the white, lightweight, crush-resistant substance commonly found in mixes. It is a volcanic rock that expands upon heating, sort of like popcorn. It is used to improve drainage and aeration. Styrofoam beads are sometimes substituted for perlite because they are less expensive. They can compact over time and do have the annoying habit of floating to the pot surface with regular waterings.
Vermiculite is another mineral often found in potting media. It is formed when mica is heated. The resulting brownish, puffy material can absorb water and nutrients, and slowly releases potassium, magnesium and calcium.

Potting mixes that do not contain actual soil are referred to as soilless mixes. When sand is added to a potting mix, it is usually sold as a potting soil. Sand, after all, is a component of soil, as is silt and clay. Potting mixes for cacti and other succulents generally contain sand for improved drainage. A heavier potting soil, as opposed to a lighter soilless media, is useful where more weight is needed, as with top-heavy houseplants. For most houseplants, however, a soilless media is perfectly suitable.

Moisten the potting mix with warm water before repotting. Carefully remove the plant from its present pot. It is a good idea to thoroughly water plants several hours to a day before re-potting. For really pot-bound plants, you may need to slide a knife or other tool around the inside of the pot to loosen it.

The roots may require a light pruning, especially if they are encircling the inside of the pot. Make 3 or 4 cuts about half an inch deep along the sides from the top to the bottom of the rootball. Sometimes it is necessary to cut the bottom inch or so of root mass off and tease the roots slightly apart before repotting. This does sound drastic, but vigorously-growing plants will recover quite rapidly, and these are the types that require more frequent re-potting. The goal is to have roots growing outward and not around in circles inside the pot.

Place enough potting mix in the new container to have your plant at the same soil level it was at before repotting. Gently but firmly fill in around the edges and water thoroughly. Keep in mind that all pots must have holes for excess water to drain. Fertilizer is sometimes added to packaged potting mixes. It usually is just a small amount and will not substitute for a regular houseplant fertilization program. Water-retentive agents may also be included in packaged mixes.

Just as you sometimes require larger living quarters, so do your houseplants. Re-potting your plants when necessary will keep them healthy, happy and looking good. If you have questions about caring for or repotting houseplants, or on other indoor or outdoor gardening topics, call the UConn Home & Garden Education Center, toll-free, at 877-486-6271, visit www.ladybug.uconn.edu or contact your local Cooperative Extension Center.


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