General plant-care information. Some houseplants are harmful to cats, dogs or children if chewed, and some sap irritates skin. Check your plant’s label or ask a vet if you have pets, and wear gloves if you’re unsure.
The pothos on your shelf has roots poking out of the bottom of its pot, the soil dries out within a couple of days, and you’re half afraid that tipping it out will kill it. Knowing how to repot a houseplant takes most of the fear away: choose the moment, pick a pot only slightly larger, handle the roots gently, and water properly afterwards. This guide follows that order, with figures from the Royal Horticultural Society (RHS) and University of Illinois Extension.
Signs it’s time to repot a houseplant
A plant doesn’t need a bigger pot because a calendar says so. Look for evidence. The RHS notes that lifting a plant out of its container is the best way to see whether its roots are congested, and that a congested mass of roots can stop water draining properly and lead to root rot. University of Illinois Extension lists roots growing through the drainage holes, roots on the soil surface, smaller-than-usual new leaves and wilting between regular waterings as signs.
| What you see | What it can mean | What to do |
|---|---|---|
| Roots through the drainage holes | Root system has filled the pot (Illinois Extension) | Repot into a slightly larger pot |
| Roots on the soil surface | Same (Illinois Extension) | Repot |
| Wilting between normal waterings | Too many roots, too little soil to hold water (Illinois Extension) | Lift the plant out and check the roots |
| New leaves smaller than usual | Possible crowding (Illinois Extension) | Check roots; also check light and feeding |
| No drainage holes in the pot | Water can’t escape (Illinois Extension) | Move into a pot with holes |
| Slow growth alone | Could be light, season or feeding | Do not repot on this sign alone |
That last row is practical advice. A plant in winter grows slowly whatever its pot looks like, and moving it won’t change that.
When to repot
The RHS says that spring, as plants start into growth, is generally the best time to repot and prune roots, and that autumn and winter are best avoided when growth slows or stops. Illinois agrees in a different way: repotting is best done when the plant is actively growing, in spring or early summer. A plant that’s growing can fill new soil with roots quickly, so it dries out and recovers sooner.
If a plant is in flower, it’s reasonable to wait until the blooms finish unless the roots are in real trouble. That’s practical advice rather than an official rule.
Choose the right pot
How much bigger
Going too big is the most common mistake. A pot with a lot of extra soil holds water the roots can’t use, and the roots sit in wet compost. The RHS says the new pot should be no more than one third larger than the current one, and also suggests aiming for a container about 2.5 to 5cm (1 to 2 inches) deeper and wider. Illinois Extension’s gardening blog says to choose a new container two inches larger in diameter than the original.
The three figures overlap in the 2.5 to 5cm range. Where they differ, pick the smaller pot. Reading the RHS’s “one third” as a diameter, the table below shows the ceiling.
| Current pot diameter | Largest new pot (one-third rule) | Typical choice (2.5 to 5cm wider) |
|---|---|---|
| 10cm | 13.3cm | 12.5 to 13.3cm |
| 15cm | 20cm | 17.5 to 20cm |
| 20cm | 26.7cm | 22.5 to 25cm |
| 25cm | 33.3cm | 27.5 to 30cm |
Pots come in set sizes, so round down to the nearest one you can buy. Example: a plant in a 15cm pot goes into an 18cm pot, not a 25cm one.
Drainage
Choose a pot with drainage holes. Illinois says that if the existing pot has none, that alone is a reason to repot. Its blog also warns against putting a layer of gravel or grit at the bottom of the pot, saying gravel doesn’t improve drainage and can make it worse. A decorative outer pot is fine if the plant stays in its plastic inner pot and you lift it out to water.
The mix
The RHS says peat-free multipurpose compost suits a wide range of container plants, and that loam-based compost, such as a peat-free John Innes mix, is a good option for long-term container planting. Illinois recommends a soil-free potting mix for most houseplants and advises against heavy bagged potting soil. Garden soil compacts in a pot, so leave it in the garden. Cacti and succulents do better in a gritty, free-draining mix. That one is practical advice, so check the label for your plant.
Repotting step by step
- Water first. Illinois Extension’s blog suggests watering an hour before repotting so the plant is hydrated and the root ball slides out more easily.
- Take the plant out. Lay a sheet of newspaper down, tip the pot sideways, and ease the plant out, supporting the base of the stem. If it sticks, squeeze a plastic pot or run a knife around the inside edge.
- Look at the roots. Healthy roots are firm and pale. The RHS says to trim off any soft, rotted roots. For circling roots, Illinois advises cutting and/or unwinding them on root-bound plants, and the RHS says a congested root ball may need teasing out and a light trim.
- Add a layer of mix. Put enough fresh compost in the base so the plant will sit at the right height.
- Set the plant at the same depth. Illinois says to repot the plant at the same depth it grew at before. The RHS says to check that the top of the root ball sits just below the rim, which leaves room for watering.
- Fill and firm. Add mix around the sides and press it gently with your fingers so there are no air gaps. Don’t pack it hard.
- Water thoroughly. The RHS says to add water until some comes out through the drainage holes. Let it drain and empty the saucer afterwards. The Illinois blog suggests emptying standing water after about 20 minutes.
When in doubt, pick the pot that is slightly too small over the one that is too big.
Aftercare in the first weeks
Keep the plant out of harsh direct sun for a week or two while it settles. This is practical advice, not a figure from either source. Water again only when the top of the mix has started to dry, because fresh compost holds water well. Neither the RHS repotting page nor the Illinois pages fetched for this guide give a feeding schedule, so follow the instructions on your plant food and hold off for a few weeks, since fresh mix usually contains some nutrients already.
A bit of drooping in the first few days is common and usually passes. If leaves keep yellowing or the stem goes soft after two weeks, lift the plant out and check the roots again for rot.
Repotting without going up a size
Sometimes a plant is already as big as your space allows. The RHS says repotting can mean replanting into the same container after refreshing the compost or root pruning, and that a light trim removing up to 15% of the root system every few years can be sufficient. If root pruning isn’t suitable for your plant, you can simply refresh some of the compost. Do it in spring, with the same care over watering afterwards.
Checklist
- Roots checked by lifting the plant out, not guessed at
- Spring or early summer, with the plant actively growing
- New pot only 2.5 to 5cm wider, and no more than one third bigger
- Drainage holes, no gravel layer in the base
- Fresh peat-free multipurpose or soil-free potting mix, not garden soil
- Soft or rotted roots trimmed, circling roots teased out
- Plant at its old depth, top of the root ball just below the rim
- Watered until water runs from the holes, then drained
- Out of strong sun for a week or two
Common mistakes
Moving a small plant into a very large pot tops the list. The second is repotting in midwinter, when the plant isn’t growing enough to use the new soil. The third is planting too deep, which buries the stem base and invites rot. The fourth is reusing old mix full of roots and salts when the whole point was fresh soil.
The takeaway
To repot a houseplant well, wait for a growing season, lift the plant out to look at the roots, and choose a pot only 2.5 to 5cm wider with drainage holes. Plant it at the same depth in fresh mix, water until it runs through, and go easy on sun and feeding for the first weeks.
