How to Repot a Houseplant

Repotting is one of those jobs people either do far too often or not at all. Done at the right time, it gives a plant room to grow and fresh soil to grow in. Done at the wrong time, or into the wrong pot, it can set a healthy plant back for months. This guide covers how to tell when it is needed and how to do it well.

Does it actually need repotting?

Most houseplants need a bigger pot every two to three years, and slow growers even less often. A plant does not need repotting just because you have brought it home. Give a new plant at least two weeks to settle first; it has already coped with a journey and a change of light.

Look for these signs:

• Roots growing out of the drainage hole or circling on top of the soil.
• Water running straight through the pot, because there is more root than soil left to hold it.
• The plant drying out within a day or two of a thorough watering, when it used to last a week.
• A plastic pot bulging or cracking from the pressure of the roots.
• Growth that has stalled in spring and summer, despite good light and care.

Some plants are happiest a little crowded and should be left alone longer than most. Snake plants and ZZ plants both prefer snug roots and grow happily when slightly pot-bound. Many palms and cacti are similar. Repot these only when the roots are clearly running out of room.

When to do it

Spring and early summer are the best times, when the plant is growing actively and can quickly push new roots into fresh soil. Avoid repotting in the depth of winter unless there is an emergency, such as root rot, a broken pot or a plant sitting in soggy, sour soil.

Choosing the pot

Go up one size only: a pot about two inches wider than the current one for small and medium plants, or up to four inches for large floor plants. It is tempting to jump to a much bigger pot so you do not have to repot again soon, but a small root ball in a large volume of soil leaves most of that soil wet and unused, and wet soil around idle roots is how rot starts.

The pot must have a drainage hole. The material is your choice, but it changes how fast the soil dries. A terracotta pot breathes and dries quickly, which suits plants that like to dry out. Plastic holds moisture longer, which suits thirstier plants. Moisture-lovers such as ferns and calatheas can also go into a self-watering pot at this stage; repotting is the easiest moment to set up the wick.

Choosing the soil

Use fresh potting mix, never garden soil, which compacts in a pot and can carry pests. Match the mix to the plant:

• Most leafy houseplants: a good general houseplant mix with some added perlite for drainage.
• Monstera, pothos and other aroids: a chunky, airy mix such as our aroid potting mix.
• Succulents and cacti: a gritty, fast-draining cactus mix.
• Ferns: a finer mix that holds more moisture.

Step by step

1. Water the plant a day before. Moist roots slide out of the pot more easily and suffer less damage than dry ones.
2. Prepare the new pot with a layer of fresh mix in the base, deep enough that the top of the root ball will sit about an inch below the rim.
3. Turn the old pot on its side, support the base of the plant between your fingers, and ease it out. Squeeze a plastic pot or run a knife around the inside of a rigid one if it sticks. Never pull the plant out by its stems.
4. Look at the roots. Healthy ones are firm and pale. Trim away any that are brown, mushy or smell bad with clean scissors.
5. If the roots circle tightly around the outside, gently tease them loose with your fingers so they grow outward into the new soil.
6. Set the plant in the new pot at the same depth it grew before. Fill around it with mix, firming gently to remove large air pockets, but do not pack it down hard.
7. Water thoroughly until water runs from the drainage hole, then let it drain.

Aftercare

Some drooping or a yellow leaf or two in the first week is normal; the plant is recovering from root disturbance. Keep it out of direct sun for a week or so, and do not feed it for about a month, since fresh mix contains enough nutrients and new roots are easily scorched by fertilizer.

The biggest risk after repotting is overwatering. The new soil holds more water than the old, exhausted mix, and the roots have not yet grown into it. Wait until the top of the soil has dried before watering again, even if that takes longer than usual. If you are unsure how often to water a freshly repotted plant, err on the side of less.

Refreshing without a bigger pot

Some large plants are already in the biggest pot you want to handle. You can still give them fresh soil. Remove the top two inches of old mix each spring and replace it with fresh, a job called top-dressing. Every few years, ease the plant out, trim around a quarter of the outer roots, and return it to the same pot with new mix around the root ball. It keeps a mature plant healthy without it outgrowing the room.