The Perfect Pot: Not Too Big, Not Too Small

Tease out congested roots before putting a plant into a larger pot. Increasing the pot diameter by one or two inches allows for two to three years of growth.
Tease out congested roots before putting a plant into a larger pot. Increasing the pot diameter by one or two inches allows for two to three years of growth. (Jupiter Images)
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By Adrian Higgins
Thursday, April 10, 2008

Houseplants look awful in April, but it's also the moment to help them spring back.

As warmer temperatures and longer days prod them into growth, the urge to burgeon allows them to recover quickly from the trauma of repotting and pruning.

So line up your ficus, citrus, philodendrons and dieffenbachias, and examine their feet.

Look for signs that the plant is pot-bound, such as using its roots as stilts to try to escape its container. Here's another indicator: If a plant never seems to get enough water, its roots may have displaced most of the soil. And the surest sign is the appearance of roots through the drainage hole.

I have a 24-year-old schefflera that now has fine white roots radiating along the floor like a slender starfish. There will be nothing delicate about its repotting.

The schefflera has been placed in progressively bigger containers through the years. This "potting up" has brought it to the heavy 18-inch clay pot it now calls home. I see a 20-inch pot in its future and some ibuprofen in mine.

Repotting is a messy affair and best tackled outdoors. A potting bench is a real boon for the back.

Don't take a plant in an eight-inch pot, say, and put it in a 12-inch one, thinking this will delay a future repotting by a few years. Too much soil will stay wet, even in a well-drained pot, and the roots will melt away. Increasing the pot diameter by one or two inches provides enough room for two to three years of additional growth.

A truly pot-bound character may be hard to release. Submerging the pot in water for half an hour may help, as will taking a knife and breaking the contact between the roots and the inside of the pot. Sometimes you have to cut away plastic pots or smash clay ones to free the plant without destroying it.

You will want to tease out congested roots before putting a plant into a larger pot, but a root ball that is a solid mass is another matter: It should be cut back on all sides by about one-third; then it can go back into the same pot.

Don't remove all the old soil: You want the root ball to remain intact, but you must use fresh potting soil when backfilling. Don't use compost, garden soil or topsoil, which are too heavy or unsterile for houseplants. Fresh potting soil, which contains soil lighteners such as perlite, will restore the nutrients and soil texture that the new roots need. A little balanced fertilizer will help as the plants develop this spring, but don't overdo it.

Place some clay pot shards or stones at the bottom of the pot, lay a little weed-blocking fabric over them, and backfill, making sure the plant is set at the same height as before. Shake the pot to get the new soil to fill in any air pockets, and keep the soil line at least an inch below the lip of the pot, to allow for thorough watering during the year. You may have to add more soil after watering.

This is also a good time to trim plants, remove rubbing or inward-growing branches, or aggressively cut back certain plants that have become too large, such as dracaenas or rubber plants. Norfolk Island pines are tropical conifers and should not be headed back.

Most houseplants are at their most stressed now after a winter indoors and may be afflicted with spider mites, whitefly, mealybugs or scale. Heavily infested plants should be discarded. With the plants outside, however, you can spray foliage with abandon, using organic products such as horticultural oil and insecticidal soap.

What I love about working with mature houseplants is that no matter how crummy their top growth appears, they have enough roots to push out a lot of fresh, clean foliage once they are happily repotted. I am thinking particularly of a Ponderosa lemon tree I have that drops most of its leaves by the time March rolls around. By June it will look the picture.

Most houseplants do well outside in the warmer months, in an area of partial shade and protection from the wind. They should not go out permanently, however, until nighttime temperatures are at least in the 50s.

The annual repotting also offers another way of perking up winter-weary houseplants: by springing for some beautiful pots. The new catalogue of high-end potmaker Seibert & Rice recently landed on my desk. I found just the pot for my lemon tree, a handmade 21-inch terra cotta beauty with a citrus swag applique. It's called the Lemon Vase. At $1,200, it's way over my budget. But a little wistful dreaming seems fitting in this month of anticipation.

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