Repotting an Anthurium and Dealing With Aerial Roots

When it actually needs repotting

Anthurium flowers better slightly snug, so repotting on a calendar does more harm than good. Most plants want it every two to three years. These are the signals that matter.

1. The plant is lifting itself out of the pot Thick roots crowding the surface push the crown upwards until it sits proud of the rim and topples. This is the classic anthurium signal and it means the root mass has run out of room.
2. Water runs straight through Water appears at the drainage holes within seconds and the mix barely darkens. The roots have filled the pot and the water is finding channels.
3. The mix has collapsed Bark breaks down over two or three years into something dense and airless. If the surface has gone fine and muddy, repot even if the roots have space.
4. New leaves keep getting smaller With good light and regular feeding, a run of progressively smaller leaves means the roots cannot supply them.

Roots showing at the surface on their own are not a problem. Anthurium is semi epiphytic and always shows some. It is the crown rising and the pot tipping that tells you to act.

Timing and pot size

Repot in late spring or early summer, when the plant is warm and growing and can replace the roots you disturb. Avoid it entirely from late autumn to early spring: cut roots do not heal in a cold pot, they rot.

Go up one size only. A large pot holds a mass of mix with no roots in it, that mix stays wet for weeks, and the plant rots in what looks like generosity.

Pick a pot with generous drainage holes. Anthurium in a pot with one small hole is a rot risk regardless of what you fill it with.

The right mix

This is the decision that matters most. Standard bagged houseplant compost, used on its own, is too fine and too retentive for anthurium roots and is behind a large share of the yellowing and rot people report. The mix should look open and chunky enough that you can see air spaces in it.

A reliable blend is roughly two parts orchid bark, two parts a peat free houseplant compost or coir, one part perlite and one part coarse horticultural charcoal. Anything with a similar structure works. What you are after is a mix that drains within seconds and still feels slightly damp two days later.

Doing it

Work somewhere you can make a mess, and have the new mix ready and slightly damp before you start. The whole job takes ten minutes and the plant should be back in light within the hour.

1. Water the day before A rootball that is damp rather than dry or sodden holds together and slides out cleanly. Repotting a bone dry plant snaps roots.
2. Ease it out, do not pull the stems Squeeze the pot, tip it, and support the crown with your hand. Pulling on the leaf stalks tears them out of the crown.
3. Tease the outside of the rootball loose Free the outer roots with your fingers and shake off the collapsed old mix. Leave the dense center alone unless it is rotten.
4. Cut away any dead roots Brown, hollow or soft roots come off with clean snips. Firm pale roots, including the thick ones circling the pot, all stay.
5. Set the crown at the right depth The base of the crown sits level with the surface of the mix, never buried. A buried crown rots. Work mix in around the roots with your fingers rather than pressing it down hard.
6. Water in once and drain fully One thorough watering to settle the mix, then let it drain completely and do not water again until it is genuinely dry.

Do not feed for four to six weeks after repotting. Fresh mix carries enough, and fertilizer on newly cut roots damages them.

Aerial roots and a rising crown

Over a few years an anthurium builds a short woody stem, sheds its lowest leaves, and ends up with the crown standing above the mix on a bare stalk fringed with aerial roots. This is normal and it is fixable, though not by burying it deeper in the same pot.

The correct fix at repotting time is to set the plant lower in the new pot so the bare stem and its aerial roots are covered with mix, up to but not including the base of the crown. Those aerial roots become ordinary roots within a few weeks and the plant is stable again. If the bare stem is too long for that, cut the top off with a good set of aerial roots attached and root it as a new plant, which is covered under propagation.

1. Do not cut aerial roots off for tidiness They are working roots. Cut only the ones that are shriveled, brown and clearly dead.
2. Wrap them if you cannot bury them Between repottings, wrap exposed aerial roots in damp sphagnum moss and keep it lightly moist. They will thicken and function.
3. Never bury the crown itself Mix over the growing point causes crown rot within weeks. Cover the stem, stop at the crown.

After the repot

For the first two or three weeks keep the plant somewhere bright but out of any direct sun, hold the temperature above 68F (20C) if you can, and resist watering on the old schedule. A freshly repotted plant in a slightly larger pot dries more slowly than the one you had last week.

A little sulking is normal. An existing flower may fade early and one older leaf may yellow. What you are waiting for is a new leaf, which usually appears within four to six weeks and tells you the roots have taken. Note the repotting date, the pot size and the mix you used, because in two years you will want to know exactly what you did.