How to Repot a Peace Lily: Timing, Pot Size and Dividing

Repot in the growing season

Repotting always breaks roots, and the plant has to replace them. That only happens while it is actively growing in a warm room, which is why the timing matters more than convenience. Spring is the ideal window and early summer works well; a repot in late autumn leaves cut roots sitting in cool damp compost for months, and they rot rather than heal.

The exception is root rot. If the compost smells sour and the roots are brown and mushy, repot immediately whatever the season, because leaving it is certainly worse.

Signs it actually needs repotting

A peace lily flowers better slightly pot bound, so repot when the plant asks rather than on a schedule. Every two or three years is typical for a mature plant.

1. It droops within days of watering This is the clearest sign of all. So much of the pot is root that it holds almost no water, and the plant runs out within two or three days however well you water.
2. Water runs straight through Water appears at the drainage holes almost immediately while the compost barely darkens. It has found channels through a solid mass of roots rather than soaking in.
3. Roots coming out of the holes Roots pushing out of the bottom, or a solid rootball that lifts out of the pot as one block with no loose compost, means it has run out of room.
4. New leaves getting smaller If light and feeding are right but each new leaf is smaller than the last, the roots cannot supply the plant any more.
5. It tips over When the crown has outgrown the weight of the pot and the plant will not stand up, the roots are equally cramped.

One size up, never more

Moving a peace lily into a much larger pot creates a mass of compost with no roots in it. That compost stays wet for weeks, and it is one of the commonest causes of root rot in a plant that was previously healthy. It also costs you a season of flowers while the plant fills the space.

To hold a plant at its current size, shave about a third off the outside and bottom of the rootball, return it to the same pot with fresh compost, and remove a few of the oldest outer leaves to balance it.

Compost and drainage

A peace lily wants compost that holds moisture without staying soggy, which is a narrower target than it sounds. Straight bagged houseplant compost is usually too dense on its own: it holds water well at first, then collapses, and the roots suffocate in the lower half of the pot.

1. A workable mix Roughly six parts houseplant compost, two parts perlite and one to two parts fine orchid bark or coir. That holds moisture between waterings while still letting air to the roots.
2. The pot must drain A pot with no drainage hole will kill a peace lily eventually, whatever you put in the bottom. Crocks or gravel in a sealed pot create a saturated layer rather than drainage.
3. Do not reuse old compost as it is Compost from an old pot has broken down, drains badly and carries accumulated salts. Replace at least half of it with fresh.
4. Choose the pot material to suit you Terracotta dries faster and forgives overwatering; plastic and glazed ceramic hold moisture and forgive forgetfulness. Pick for the way you actually water.

Doing the repot

Water the plant the day before so the rootball holds together and the roots are not already stressed. The whole operation should take ten minutes, and the less time the roots spend in the air the better.

Some wilting in the first few days afterwards is normal, because the plant has fewer working roots than leaves to supply. Resist the urge to water again straight away: sitting in wet compost with damaged roots is how a sulking plant becomes a dead one. Keep it out of direct light and away from drafts for two weeks, and do not feed for about a month, because fresh compost holds enough and fertilizer on newly cut roots does harm rather than good.

Record the date of each repot, the pot size before and after, and how many crowns the plant had. Three years on that tells you at a glance whether it is due, and whether the last repot was followed by good flowering or a blank year. Note what the roots looked like too, because knowing they were white and firm last time makes the beginnings of rot far easier to recognize next time.

1. Ease it out Squeeze a plastic pot or run a knife around a rigid one, then lift the plant by the base of the crown rather than pulling on the leaves. Support the rootball from underneath.
2. Inspect and tidy the roots Healthy peace lily roots are white to pale cream and firm. Cut away anything brown, soft or smelling sour. Tease the outer roots loose if they are circling the rootball.
3. Set it at the same depth The crown must sit at the same height in the compost as before. Burying the crown rots it, which is a common and avoidable way to lose a plant.
4. Fill and settle without ramming Work fresh compost around the sides and tap the pot down to settle it. Do not compact it hard with your thumbs, or you undo the drainage you just built.
5. Water in once, thoroughly Water until it drains freely, then leave it alone. This is the one time to water regardless of what the compost was doing. Normal watering resumes once you see new growth.

Never repot and divide, or repot and cut back hard, on the same day. One operation at a time, with weeks between them.

Dividing instead of potting up

A peace lily grows as a clump of crowns, and after a few years it is often better to divide it than to keep moving it into bigger pots. Division gives you several plants at a manageable size, and each divided piece flowers well because each is snug in its own pot.

Divide in spring, at the same time you would repot. Take the plant out, shake the compost off enough to see the crowns, and pull or cut the clump into sections with at least two or three leaves and a good share of roots each. A single leaf with a scrap of root will not establish.

1. Separate by hand where you can Work the crowns apart with your fingers rather than cutting. The natural separation points give the cleanest divisions and the least damage.
2. Use a clean knife where you must For a solid old clump, cut down through it with a sharp clean blade, keeping roots on both sides. Do not saw at it.
3. Pot each piece snugly Use the smallest pot that takes the roots comfortably. A division rattling around in a large pot sits wet and rots.
4. Keep them warm and shaded Divisions establish over three to four weeks. Keep them out of direct light, damp rather than wet, and do not feed until new leaves appear.

The sap contains calcium oxalate crystals and irritates skin and mouths. Wear gloves when dividing, and keep the offcuts away from children and pets.