There is no specific season for repotting houseplants: it can be done in spring, summer or fall, as long as the plant is growing (it’s best not to repot a plant when it is beginning its dormancy). But many plants grow very quickly over the summer (some even double in size!) and by fall are practically pouring out of their pots. It’s therefore logical to consider repotting at least these plants in the autumn.
One way to determine if a plant needs repotting is to consider how often it needs to be watered. If a weekly watering seems sufficient, it’s probably quite happy in its current pot, but if it shows signs of distress after 3 or 4 days, with leaves that begin to wilt, that’s usually because the pot is so filled with roots the soil is not able to carry out its usual role of water reservoir. That suggests that repotting is necessary.
How to Repot
Choose a pot of about 2 inches (5 cm) larger than the previous pot (for small to medium-sized plants) or 4 inches (10 cm) larger (for large plants). It must have one or several drainage holes.
Prepare the potting mix in advance, watering lightly, as moist soil is easier to manipulate. Consider adding a mycorrhizal inoculant to the potting mix. It contains beneficial fungi lacking in most commercial potting soils. Cover the drainage holes with a small section of newspaper or insect screen to prevent the potting soil from flowing out when you water.
To remove the plant from its pot, invert it by holding the stem between the fingers of one hand and giving a firm tap on the bottom of the pot with the other. This should free the root ball, allowing it to slip out of the pot. If the plant doesn’t budge, try running a knife between the root ball and the pot, then repeat. Sometimes you have to smash or cut the pot to extract the plant.
Now study the root ball, cutting away roots that appear dead or rotten and those circle the pot. Then, with your fingers, work some of the old soil free. Be especially sure to remove the soil at the top of the root ball: this is where, over time, potentially harmful mineral salts tend to accumulate.
Add moistened soil to the bottom of the new pot, enough so that the root ball will at the right level (about 1 inch/2.5 cm below edge of the pot). Do not add a “drainage layer” to the bottom of the pot: it’s unnecessary and can even be harmful. Center the root ball in the pot and fill the gap with potting mix, using a spoon or chopstick to work the soil in among the roots. Tamp down a bit with your fingers and water.
There you go: it’s already done! Now just move the plant out of direct sunlight for two or three days while it recuperates, then put it back in its usual spot. Nothing could be easier!