Released: April 12, 2004

Spring Houseplant Growth May Call for Larger Pot

MANHATTAN, Kan. – Indoor plants usually stage a growth spurt in spring, while outdoor plants are leafing out. They’re responding to the longer days.

So, houseplants may need to move into a larger pot, even before some of them go outside in May to spend summer in a sheltered site.

“Indoor plants can become root-bound, just as patio and window box plants do. In fact, most houseplants need to be repotted every year, although a few can be unusually fast or slow growers,” said Ward Upham, horticulturist with Kansas State University Research and Extension.

The measure of whether an indoor plant needs room is not the same as gardeners use with outdoor container plants or purchased transplants.

“If you can see a clear network of roots on a houseplant’s root ball, it needs to move up to a larger pot,” Upham said. “The plant may never recover if you wait until the roots are circling the bottom or growing out of the drainage holes.”

A much bigger container isn’t the next logical choice, though. Too-big pots make preventing root rot much harder, the horticulturist said.

Plants that are growing in a pot that’s 10 inches wide or less should move into one just 1 inch wider than their current home. Plants in pots that are more than 10 inches in diameter should move into one 2 inches wider.

Because checking houseplants’ root ball tends to be messy and sometimes difficult, Upham often suggests running the test outdoors on a mild day, several hours after watering the plants.

“Watering helps their root ball come out more easily,” he explained.

Trying to release a root ball by tugging on the plant’s stem is NOT a good idea, Upham said. The plant may snap off. Or, it may come out of the soil like a pulled weed, leaving many of its roots behind.

“With small pots, just slide the plant’s stem between two fingers as you place that hand over the top of the pot. Turn everything upside down. If that doesn’t make the root ball slide out, rap the edge of the pot on a table or such. Then the plant should come free,” he said.

Larger pots can be a bigger challenge, particularly if the roots are crowded.

“Place the pot on its side and rap its top edge with a rubber mallet. Turn the pot a few degrees, rap again and keep repeating that procedure until the established root ball comes loose, intact,” Upham said.

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K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.

Story by:
Kathleen Ward
kward@oznet.ksu.edu
K-State Research& Extension News