by BRIAN MINTER
July 1, 2004
If there ever was a perfect time of year to repot houseplants, this is it. Early summer is the ideal time to change the pots and soil around all our houseplants because they still have two months of fine growing weather to settle in before stressful winter conditions arrive. Now, don't assume every plant around the house needs repotting! The second most serious cause of plant death (the first being over-watering) is over-potting. The only reason any plant in your home needs repotting is if it is rootbound. Virtually all plants love to be 'pot bound' - in fact, many will not grow until the roots have begun to wrap themselves around the inside of a new pot. Ivies are a prime example. Try to get them to grow after transplanting - they simply don't move until roots have filled up their new home.
Transplanting needs to be done carefully, quickly and the new pot should be only slightly larger than the old one. A general rule of thumb is: transplant into a pot two inches larger than the previous one. Many rootbound plants are sitting in soil which has been drained not only of fertilizers but also of organic matter, and many old soils are hard and crusty. Water absorption is minimal because barren soil and massive roots allow little moisture retention. Oxygen, which is so important to a plant's survival, cannot penetrate in and around the roots, and without repotting, these plants soon begin to go backwards.
When selecting a pot, the most important consideration is drainage. I hear all sorts of stories about plastic pots not being satisfactory. Not so! Any type of pot is fine as long as it provides good drainage. Clay pots are terrific for most plants because of clay's ability to breathe and absorb excess moisture. Keep in mind, however, that salt buildup in the soil can discolour clay, leaving a white residue, and algae often forms on the outside. New easy-to-apply sprays can prevent both algae and general guck from messing up your clay containers. Also, make sure your pots have holes for drainage. Heavy ceramic pots look great, but many of these fancy pots should not be used for growing plants, but should rather be used as a container for the growing pot.
The soil you select for repotting should have three qualities: it should be sterilized, contain porosity materials such as perlite or pumice, and it should have good drainage, yet it must also have moisture retention capabilities. There are many fine soils on the market, but beware of the ones that contain too much sand. You may wish to add a little 'Root Booster' to encourage fast root development, and weekly feedings of 20-20-20 fertilizer after transplanting will help your plant get reestablished.
Before transplanting, make sure your plants are moist. Ripping a dry rootball from a pot will destroy many root hairs and cause set-back. If a plant is terribly rootbound, soak it in warm water with a little 'Root Booster' until it stops bubbling - then gently loosen the ball with your hands and ruffle the outside roots. Set the rootball into its new pot, keeping the top of the soil at the same depth as it was before. A serious mistake made by most people is packing the new soil too firmly around the rootball. Simply place the soil around the ball, tapping it gently with your fingers, then tap the pot once or twice to settle the soil in. Let water do the rest as you puddle the soil in place with a thorough drink of warm water.
Newly potted plants should be near an east or north window for a few days to help them become acclimatized, then they are ready to go back to their growing area. Water sparingly after the initial watering. Remember: water well, but let the plants dry out between waterings. The best way to tell if your plant needs watering is by lifting the pot and feeling the weight. If it feels heavy, the plant does not need watering; if it feels light, the plant is dry and should be watered. As the roots develop and take hold, your plant will continue to grow and be well established before winter.