If you manage to keep alive a houseplant for, oh, more than a few months, there will surely come the day when it has outgrown its starter pot. The roots will be tangled. It will be gasping for air. It is especially wise to check in on your potted plants at winter's end (especially in certain climes), when the promise of vernal sun brings on hardy growth spurts, and your ready-to-burst houseplant begs for roomier real estate. (Some signs of a houseplant in need of roomier digs: It's top-heavy for the pot, or when roots start emerging from the existing pot's drainage holes.)
We checked in with Eric Larson, a houseplant wunderkind and manager of Yale University's Marsh Botanic Gardens in New Haven, Conn. He walked us through the not-so-slippery terrain of repotting your root-bound houseplant. Please, play along at home.
Degree of difficulty: Easy.
Tools required: Old newspapers. Clippers or pruning knife. Potting soil (with vermiculite or perlite). New, clean pot that is no more than 25 percent bigger than existing pot. Garden gloves.
1. Place old newspapers on a flat work space about the size of your kitchen sink. (If it's mild enough to do this outside, even better.) Gently remove your root-bound houseplant from its too-tight pot; this may require some light nudging.
2. Examine the root ball. Use a pruning knife or closed pruning clippers (your fingers will work, too) to gently tease out the roots, as if untangling a knot of hair — you are providing breathing room. Blackened roots indicate that the root is dead; cut it off. Be sure to do this on all sides of the root ball or the plant will be lopsided.
3. Slip your newly untangled/pruned houseplant into its new pot (no more than 25 percent bigger than the old one) to make sure you have at least 1 inch of headroom for every 8 inches of soil, so you can water without water spilling over the sides. Figure out how much potting soil you can tuck into the pot and still have adequate headroom. Now, take the houseplant back out of the new pot.
4. Add potting soil to the bottom of pot. Slip the plant back into its new home, filling in the sides with as much potting soil as you need. Tamp down the soil, and the plant. Water well to get rid of air pockets. Add additional soil if necessary.