By Diane Heilenman
The Louisville Courier-Journal

New gardeners often want to know if they have to repot houseplants every spring.

Of course not. But it is a good idea to repot every other spring.

Two years in the same pot and the same tired old soil is long enough for any plant. But before you launch into this spring potting rite, which some gardeners do indeed undertake annually, it helps to know the lingo - and a few techniques.

"Potting-up" means giving a plant a larger pot; "potting-down" means the opposite; "repotting" means - strictly speaking - replanting back in the same pot. If you opt not to do any of these, you should at least "top-dress," which means removing the top few inches of soil and replacing it with fresh soil.

"Soil" itself is a tricky word in the repotting world, as most people use "soilless" potting mixes.

Pot-up when a plant is top-heavy, dries out in a day or so, has roots busting out the bottom, or has roots pushing the plant over the rim of the pot.

Potting-down might be appropriate for a plant that has lost roots to rot or is too small for its pot.

Repot when you don't want or need to resize to solve "ugly pot syndrome" - which can refer to a build-up of salt deposits or an aesthetic deficit in the look of the plant and pot together.

Top dress when you have a very large pot or if the plants tend to go into a nosedive when repotted, like clivia, cactus and amaryllis.

Repotting techniques

Give the chosen plants a preliminary watering a day or two before the repotting marathon.

Assemble materials, including potting mix and pots. You need not buy new pots but, if you are reusing empty pots, wash them and (if possible) let them soak in a dilute (10 percent) bleach solution to get rid of possible pathogens.

Unpot. Generally, all you have to do is upend the pot or tip it over, capturing the plant in your spread fingers and pulling it out of the pot.

If the pot is too big to hold, tip it over on the ground and gently tug out the plant, being certain not to snatch off leaves or stems.

If it is stuck, you must break the clay pot or cut apart the plastic pot.

Prune. Always remove dead, dry, rotten roots and any circling roots.

Also, you can remove 1/4 to one-third of the roots safely to make the root ball smaller and/or to encourage more and smaller feeder roots.

Remove old potting mix. Loosen the old mix from the root ball with a chopstick or shake it loose gently or, very gently, roll the root ball.

Select the proper pot. Forget the old idea that you had to fill the bottom with gravel or pot shards. Dump in enough of the premoistened mix to make a good cushion.

It can be helpful to make a cone of new soil in the pot's center to support an open root mass. Sift new mix evenly around roots, trying not to mash it down hard but also trying not to leave air pockets.

Replant at the same level as before. Be certain to leave the soil level at least 1 inch below the pot rim to avoid soil runoff during watering.

Water. Watering from below rather than above is preferable. Set the repotted plants in a tub of tepid water until moisture beads on the soil surface, then put somewhere to dry.