Repotting a Kalanchoe: Small Pot, Gritty potting mix, and Never in Flower

When it actually needs repotting

A kalanchoe is happy slightly pot-bound and does not need moving every year. Repot when the plant tells you to, which for this species is usually every second spring. Doing it more often than that gains you nothing and increases the risk of rot.

1. Water runs straight through If a thorough watering drains out of the base within seconds, there is more root than compost in the pot. That is the clearest single sign that it is time.
2. Roots showing at the drainage hole Thick roots visibly circling the base or pushing out of the hole mean the rootball has filled the pot. Tip it out and look at the sides of the rootball to confirm.
3. It dries out in two days A plant that needs water twice a week in spring has no compost left to hold any. This is a root problem, not a watering problem.
4. The plant is top heavy and tips over A leggy plant in a small pot falls over and snaps its own stems. Move it into a heavier pot, and cut it back at the same time.
5. It has been two years in the same compost Compost breaks down and holds more water as it ages, so even a plant with room left benefits from fresh gritty potting mix every second spring.

Repot in spring, and never while it is in flower

Cut and disturbed roots only regrow while the plant is warm and growing, so spring after flowering is the window. A kalanchoe repotted in autumn goes into the cold with damaged roots and often loses its stem base over winter.

Repotting a plant in full flower makes it drop its blooms almost immediately, because the roots stop supplying the flower heads while they recover. If it is flowering, enjoy it, cut it back when the blooms fade, and repot after that.

Pot and compost

The most common mistake is generosity. Moving a kalanchoe into a pot several sizes larger surrounds a small root system with a large volume of compost that stays wet for weeks, and the stem base rots long before the roots ever reach the sides. Go up one size only: about an inch (2 to 3 cm) more diameter than the pot it is in.

For compost, use a cactus and succulent mix, or make your own by adding a third by volume of perlite, coarse grit or pumice to an ordinary peat-free potting mix. What you are aiming for is a mix that wets through when you water and dries through within a week.

An inch (2 to 3 cm) of coarse grit or broken crocks in the base improves drainage and adds weight low down, which stops a tall plant tipping over.

Doing it

Work with the compost on the dry side. A dry rootball crumbles away from the roots cleanly, whereas a wet one tears them, and dry cut surfaces are far less likely to rot afterwards.

1. Stop watering for about a week beforehand Let the compost dry right through. This single step prevents most of the rot that follows repotting, and it makes the whole job easier to handle.
2. Tip it out and crumble the old compost away Lay the pot on its side and ease the plant out by the base of the stem, not by the leaves. Work about a third of the old compost off the rootball with your fingers.
3. Cut away dead roots Healthy roots are pale and firm. Cut off anything brown, hollow or slimy with clean pruners, and if you find soft brown tissue at the base of the stem, cut above it and root the top instead.
4. Plant at the same depth Set the plant so the point where the stem meets the roots sits at the same level as before. Buried deeper, the stem base sits in damp compost and rots.
5. Firm gently and leave a watering gap Fill around the rootball with fresh gritty potting mix and tap the pot to settle it rather than pressing hard. Leave half an inch (1 cm) between the compost and the rim so water does not run over the edge.
6. Wait three days, then water once Leave it dry in bright shade for three days so any cut surfaces seal. Then water thoroughly once, and go back to the normal interval from there.

The first few weeks, and what to record

Recovery is quick if the pot is the right size and you kept it dry at the start. Expect visible new growth within three or four weeks in spring. Hold off feeding for a month, because fresh compost carries enough nutrient and a newly cut root system cannot use more.

Write down the date, the pot size you moved into and the compost you used. Two years later, when you are deciding whether to step it up again, the pot size alone answers the question, and if a plant rots you will be able to see whether the pot you chose was too large for it.

If the leaves go limp in the first week after repotting, do not water again. It is almost always root disturbance rather than thirst, and a second watering onto damp compost is what turns a sulking plant into a rotting one.