How to Repot a Calathea Without Setting It Back

Late spring, and only when it needs it

Calatheas resent root disturbance more than most houseplants, and a plant repotted in the wrong season can sulk for months, dropping leaves and refusing to grow. Repot in late spring or early summer, when the room is reliably above 68F (20C) and the plant is actively pushing new leaves.

Do not repot annually out of habit. This plant is happiest slightly snug in its pot, and every repotting costs it a few weeks. Once every two years is right for most plants, and three years is common for a mature one.

Signs it actually needs a bigger pot

Look for the plant telling you, rather than working to a schedule. Two or more of these together mean it is time.

1. Roots out of the drainage holes Pale roots emerging from the bottom of the pot, or visible circling on the surface, mean the pot is full. Slide the plant out and look at the sides of the rootball to confirm.
2. It dries out within two or three days When there is more root than compost, the pot cannot hold enough water and a plant that used to go a week now wilts in three days. This is the most reliable single sign.
3. Growth has stopped in the growing season No new leaves through a warm bright spring, with correct watering and feeding, usually means the roots have nowhere to go.
4. The clump has spread to the rim Calatheas grow as a clump of shoots that widens outwards. When shoots are pressed against the edge of the pot, it is either a bigger pot or a division.

New leaves coming through smaller than the last is not on its own a reason to repot. Check the light first, because that is the far commoner cause.

One size up, and drainage holes

Move up one pot size, roughly one to two inches (2.5 to 5 cm) more in diameter. A much larger pot leaves a wide collar of compost that no root reaches, and it stays wet for weeks, which is exactly how a healthy calathea gets root rot.

Depth matters less than width, because the root system is shallow and spreads sideways. A wide, shallow pot suits this plant better than a deep narrow one and dries more evenly.

Plastic or glazed ceramic suits a calathea better than bare terracotta, which wicks moisture out through the walls and dries the compost faster than these roots like.

A mix that holds damp without going airless

The mix has to do two contradictory things: stay evenly damp between waterings and still let air to the roots. Straight bagged houseplant compost fails on the second, and a cactus mix fails on the first.

1. A mix that works About five parts peat free houseplant compost, two parts perlite, two parts fine orchid bark and one part coarse sand or grit. The bark and perlite hold the structure open as the compost breaks down.
2. Add coir if your room is dry A part of coir in place of some of the compost holds moisture without becoming heavy, which helps in a heated room where the pot dries fast.
3. Skip the crocks A layer of stones in the bottom does not improve drainage. It raises the wet zone in the pot. Use a mix that drains and a pot with real holes instead.
4. Do not reuse old compost as it is Old compost has collapsed, drains poorly and carries the salts you have been trying to flush out. Replace at least half of it with fresh.

Doing it, and the fortnight afterwards

Work quickly, keep the roots out of the air for as short a time as you can, and disturb the rootball as little as possible.

1. Water the day before A damp rootball holds together and slides out cleanly. A dry one crumbles and tears the fine roots as it goes.
2. Ease it out and leave the rootball alone Support the crown, tip the pot and slide it out. Tease out only roots that are circling tightly. Do not wash the roots or shake off all the old compost unless you are dealing with rot.
3. Plant at the same depth The crown must sit at exactly the level it was before. Buried, it rots. Proud of the surface, the shallow roots dry out.
4. Water in once, then wait Water thoroughly to settle the compost around the roots, let it drain fully, and then do not water again until the top inch has dried. Freshly cut roots in soaking compost rot.
5. Give it a fortnight of easy conditions Somewhere warm and out of direct light, with the humidity up, and no fertilizer for a month. Expect a couple of drooping days and one or two older leaves to go. That is normal.

Write the date on a label pushed into the pot, along with the pot size and what mix you used. In two years' time that label answers the only questions you will actually have.