At a recent talk by a skillful gardener, I learned new techniques for repotting plants in containers.
First, let’s review the usual approach to this routine process.
When a plant has outgrown its container, the goal for repotting is to encourage and support the plant’s further growth.
The signs that a plant has outgrown its containers include roots growing out of the drainage hole, or roots filling the container (observed after lifting the pant from its container), or an abundance of multiple shoots or offsets. Additional signs of a pot-bound plan: a plastic nursery pot might bulge with the plant’s roots, or the soil in the container dries out quickly.
When the gardener observes the beginnings of such signs, it is time to remove the plant from its container and replant it in a larger container with fresh potting soil and irrigate to settle the soil around the roots. The common wisdom is to move the plant into the next larger container, e.g., from a one-gallon pot to a one-and-one-half gallon pot.
When a plant becomes significantly root-bound, however, good practice calls for root pruning. If roots have been circling the pot, cut through the roots with a hand pruner, and in some cases, peel away the outer layer of roots. If the roots are packed tightly in the pot, loosen the roots, cut away up to one-third of the roots, and make vertical cuts about one-third of the way up from the bottom of the root ball. These actions will stimulate the growth of new roots.
When reducing the root ball in this way, it could be appropriate to replant the plant in the same pot it had outgrown. This might be desirable when the gardener favors the container, or the container complements the plant nicely.
During this process, cut back a proportionate amount of the top growth to reduce the plant’s demand on its reduced root structure. In a short time, the plant will recover from repotting and resume vigorous growth.
Briefly, these are the usual steps to take to rescue a root bound plant and help to continue growing.
Then, Keith Taylor’s eye-opening talk and demonstration for the Monterey Bay Area Cactus & Succulent Society introduced different goals and techniques for repotting plants.
Taylor has been growing cacti and succulents for about twenty-seven years, with a previous background in bonsai cultivation. He has developed bonsai-related techniques for cultivating succulents, with an emphasis on caudiciform plants. Those are plants that develop a swollen trunk, stem or root—called a caudex—that stores moisture. These unusual plants are candidates for bonsai treatment and often favored by collectors.
(Note: The specimen shown here is a Euphorbia, which is not a caudiciform.)
Instead of repotting plants to encourage and accommodate growth, Taylor seeks to limit their size, promote larger and wider caudices, and stimulate compact top growth.
In pursuit of these goals, Taylor’s distinctive approach to repotting includes severe pruning of the plant’s roots and top growth. Without hesitation, he would cut off a plant’s taproot and close to all its fibrous roots to reduce the root ball to fit into a shallow bonsai pot. With some caudiciforms, he would cut the caudex literally in half, and wait for it to develop new roots.
Top growth pruning was equally extensive with the same objective of constraining the plant’s overall growth.
The roomful of avid gardeners of cacti and succulents understood Taylor’s bonsai pruning method, although this approach to gardening was unfamiliar them. These gardeners were familiar with limiting the size of their plants by keeping them in small containers with lean soil mixes and minimal moisture.
At the same time, many were astonished by Taylor’s relatively extreme pruning practices, which freely exceed the usual guideline to remove no more than one-third of a plant’s roots or top growth. While Taylor admitted that some of his early trials of such pruning were unsuccessful, he has found that many plants tolerate this treatment and respond well in time.
The gardeners in attendance learned that the one-third rule for pruning could be overly conservative and that more severe pruning could be effective in limiting plant growth. Bonsai-style pruning of cacti and succulents remains as a specialized form of container gardening and not everyone’s preference we learned that extreme pruning does not necessarily kill a plant.
Taylor’s distinctive pruning practices are closely related to his work in creating containers for plants. Examples of his extraordinary ceramic pots can be viewed on his website, and his Facebook page, where he is known as “Kitoi” (his childhood nickname).
Even when we know basic gardening methods, new knowledge is always ready for discovery.