Identium
When to Repot a Houseplant (and When to Leave It Alone)
Repotting is the fix people reach for when a plant looks sad. Half the time it is the thing that finishes it off.
A plant looks unhappy, so you buy a bigger pot. It seems generous. It is also the single most common way people kill a houseplant that was going to be fine.
Here is when a plant genuinely needs repotting, when it does not, and how to do it without setting the plant back for a season.
Signs it actually needs a bigger pot
- Roots coming out of the drainage hole, or circling visibly on the surface.Yes, repot
- Water runs straight through in seconds and the plant is thirsty again in two days. The pot is more root than soil.Yes, repot
- You tip it out and see a solid mat of root with barely any soil visible.Yes, repot
- Growth has stopped for a full season despite good light and feeding.Probably
- The plant is top heavy and tips over.Yes, but mostly for stability
- White crust on the soil surface or the pot rim, and it has been years. Mineral buildup, and fresh mix fixes it.Repot or top-dress
Signs that look urgent and are not
Yellow leaves. Almost always watering or light, not pot size. Repotting a plant with root rot into a bigger pot makes it worse, because you have added more wet soil.
Drooping. Check the soil first. Wet soil and a drooping plant is root damage, and the answer is smaller and drier, not bigger.
You just bought it. Give it a month. It is adjusting to your light and humidity, and repotting adds a second shock on top of the first. The exception is if it arrived sitting in sodden soil.
It has been a year. Time is not a reason. Plenty of plants are happiest snug, and some flower better when slightly root bound, including peace lily, spider plant, hoya and most orchids.
The pot size mistake
This is the one that matters.
Go up one size. Two to five centimetres, or one to two inches, of extra diameter. That is it.
Putting a small root ball into a big pot surrounds it with a large volume of soil that no root can reach. That soil holds water for weeks, has no roots drinking from it, and goes stagnant. The plant sits in the middle of a cold wet mass and rots, and the owner concludes it needed even more room.
If a plant has genuinely outgrown a pot by a lot, step it up over two seasons rather than in one jump.
When to do it
Early spring, as growth is starting, is ideal. The plant is about to push new roots and will fill the new soil quickly.
Repotting in autumn or winter is not fatal, but recovery is slow because the plant is barely growing. If the reason is root rot, ignore the season entirely and do it today. Rot does not wait for March.
How to do it without setting the plant back
Water the day before. A slightly damp root ball holds together and slides out. A bone dry one crumbles and tears roots.
Get it out properly. Support the base of the stem, turn the pot upside down, and squeeze or tap the rim. Never pull the plant out by the stem. If it will not budge, run a knife around the inside edge.
Look at the roots while you have them out. This is the free health check most people skip. Firm and pale is good. Brown, black or slimy is rot, and gets cut off with clean scissors.
Loosen the bottom third. If roots are circling tightly, tease them apart or make three shallow vertical cuts down the sides of the root ball. It feels wrong. It stops the plant continuing to strangle itself in a circle.
Do not bury the stem deeper than it was. Same soil line as before. Burying the stem invites rot.
Do not add gravel to the bottom "for drainage". This is stubborn folklore and it is backwards. A layer of gravel raises the saturated zone in the pot closer to the roots. Use a pot with a hole and a mix that drains.
Water lightly and hold off feeding. Fresh compost has enough nutrition for a couple of months, and fertiliser on disturbed roots does harm. Wait four to six weeks.
Which pot
Terracotta breathes and dries roughly twice as fast as plastic or glazed ceramic. Ideal for succulents, cacti, snake plants and anyone who overwaters. Annoying for ferns and calathea.
Plastic and glazed hold moisture longer. Good for moisture lovers and for anyone who forgets to water.
Drainage hole, always. If you love a pot without one, keep the plant in its nursery pot and drop that inside, then lift it out to water.
The alternative nobody mentions
If a plant is at the size you want it and you would rather it stayed there, do not repot at all. Top-dress instead: scrape off the top two inches of old soil and replace with fresh mix, once a year. The plant gets new nutrients, you get no size increase and no transplant shock.
Not sure whether your plant is one that likes being snug? It varies a lot by species, and it is one of the things Identium tells you along with the identification. Photograph a leaf with the stem visible and you will get the species plus what it actually wants from its pot.
Frequently asked questions
How do I know if my plant needs repotting?
Roots emerging from the drainage hole or circling on the surface, water running straight through in seconds, or a solid mat of root with almost no soil when you tip it out. Yellow leaves and drooping are usually watering or light problems, not pot size, and repotting for those often makes things worse.
How much bigger should the new pot be?
One size up, meaning about two to five centimetres or one to two inches more in diameter. A much bigger pot surrounds the roots with soil they cannot reach, which stays wet for weeks and rots the plant. If a plant has badly outgrown its pot, step it up over two seasons instead of one jump.
What time of year should I repot?
Early spring as growth restarts is best, since the plant will fill the new soil quickly. Autumn and winter repotting works but recovery is slow. The exception is root rot, where you should repot the same day you find it regardless of season.
Should I put gravel in the bottom of the pot for drainage?
No. This is a persistent myth and it does the opposite of what people expect. A gravel layer raises the saturated zone in the pot closer to the roots rather than draining it. Use a pot with a drainage hole and a free draining mix instead.
Can I repot a plant that has just been bought?
Wait about a month unless it is sitting in sodden soil. A new plant is already adjusting to a change in light and humidity, and repotting adds a second shock on top of the first. Most plants will drop a leaf or two during that settling period, which is normal.