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Index : Container Plants & Patio Gardening
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- 2. Repot or Not - Depends on the Plant - Top
- For the majority of plants we grow in containers, being pot-bound is a bad thing! As roots grow in the confined space of a pot, they eventually run out of room. In addition, potting soils, usually high in organic matter, eventually break down and oxidize. Over time, as the soil disappears, the mass of roots just can’t absorb adequate amounts of water and nutrients. Plants depleted of nutrients become stunted and turn yellow. Flowering plants cease to flower and fruiting plants bear no fruit! So how do you determine if a plant is pot bound and what should you consider when repotting crowded plants?
Pot bound plants usually have smaller than normal stems and stunted leaves with little or no new growth. Most suffer from nitrogen deficiencies and look pale and anemic. In addition, plants held in pots for a long period of time often suffer from leaf burn due to an excess build-up of salts in the soil. You can often see the accumulated salts as a white crusty build-up on the soil surface or on the outside of clay containers.
The most definitive test for cramped roots is the table knife test. Using a table knife or other relatively thick and dull knife, try sliding the knife down the inside edge of the pot. You won’t be able to force it down more than a few inches below the soil if roots are crammed up against the pot wall. If things are really bad, roots will be pushed up above ground, wrapping their way around the pot rim. Check the bottom of the pot to see if any sizeable roots are protruding out from the drainage hole. All signs that your patio or house
plant needs a new, larger home.
As you would imagine, pot-bound plants can be difficult to remove from their containers. Using a long, sharp kitchen knife, slide it down the inside edge of the pot, all the way around if you can. This will help separate the roots that are pressing into the pot. Cut any roots growing out of the drainage hole. Then let the soil dry some. As potting soil dries, it shrinks back from the pot edge, making extraction of the root ball easier. Just don’t let it dry too much or the plant will suffer!
Carefully remove the plant from it’s pot. Small pots can be turned upside down while holding one hand over the soil surface and allowing the root ball to slide out. Larger pots too heavy to hold up should be placed on their sides and the plants gently pulled out. If the plant just won’t budge, break the pot and remove the clay pieces. Plastic pots can be cut off with a wire or tin shears. Better to sacrifice the pot than loose the plant from rough handling!
Once the plant is free and the roots are exposed, prune away any large, finger-sized roots wrapping themselves around the outer edge of the root ball. Smaller roots should be pulled away from the outer edge of the root ball with a three-pronged garden fork. A table fork will do for smaller plants.
A word of caution - don’t over pot! Choose a new container just slightly larger than the old one. Plants languish in over-sized pots. Even if ultimately the plant will need a bigger pot, step it up in stages.
As you fill around the root ball with fresh potting soil, tamp it down with your fingers to make sure the area between the root ball and the inside pot edge have no air pockets. Then after filling the container with potting soil, water to settle and thoroughly wet the soil.
Not all plants mind being pot-bound. Some actually thrive in cramped quarters! Aloes, umbrella plant, ficus, agapanthus, asparagus fernspider lilies, and many clumping cacti seem to grow best when roots become crowded in the pot! The split-leaf philodendron (Philodendron selloum) [spreading philodendron shows it’s favor for cramped conditions by producing somewhat strange ‘other- worldly’ white, tubular roots that sprout out from the trunks of larger specimens.
Written by John Begeman, College of Agriculture and Life Sciences, the University of Arizona,
520-626-5161.
- Updated: December 9, 2007
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