Repotting Aloe Vera: Pot Size, Gritty potting mix and a Dry Week After

When it actually needs repotting

Aloe is not in a hurry to be repotted and grows perfectly well slightly tight. Most plants need it every two or three years, and repotting more often than that produces soft growth and a plant that never fills its pot.

The signs are physical rather than subtle, and any one of them on its own is enough.

1. Roots coming out of the drainage hole Thick pale roots emerging from the bottom, or a mat of them across the base of the pot, means the rootball is full. This is the most reliable single sign.
2. The plant is wider than the pot When the rosette overhangs the rim by a good margin the plant becomes top heavy and tips over, and a plant that repeatedly falls ends up with creased and snapped leaves.
3. Water runs straight through If a thorough soak drains out within seconds, there is very little compost left in the pot. Roots and pups have displaced it.
4. The pot is solid with pups A crowded clump competes with itself for water and light. Separate the pups and repot the parent at the same time.
5. The compost no longer dries Old compost breaks down into a fine sludge that holds water for weeks. If the drying time has doubled without the position changing, replace it regardless of the roots.

Repot in the warm half of the year, with dry compost

Cut and broken roots have to be replaced before the plant can take up water again, and that only happens while it is warm and growing. Repotting in cold weather leaves the plant sitting with open wounds in compost it cannot use.

Dry compost is the other half of it. A dry rootball crumbles cleanly away from the roots, so you break far fewer of them, and any surface you do break seals rather than rots. Stop watering about a week beforehand.

Pot and compost

The two decisions that matter here are both about drainage. Aloe will forgive poor compost in a small clay pot far more readily than good compost in a large plastic one with no hole.

Ordinary houseplant compost on its own stays wet far too long for an aloe. If it is all you have, cut it by at least a third with coarse grit, perlite or fine bark before you use it.

How to repot

Aloe leaves are heavy and snap at the base if you handle the plant by them. Support it by the base of the rosette throughout, and wear gloves if your plant has firm spines along the leaf margins.

1. Stop watering a week before A dry rootball is the single thing that makes this job easy. Wait for the compost to be bone dry to the bottom of the pot before you start.
2. Slide the plant out sideways Lay the pot on its side, squeeze a plastic pot or tap the rim of a clay one, and draw the plant out by the base of the rosette. Never pull on a leaf.
3. Crumble off the old compost and inspect the roots Work most of the old compost away by hand. Healthy aloe roots are firm and pale, often orange-tinted. Anything black, hollow or slimy is dead and must come off.
4. Cut away dead roots and separate any pups Trim rotted roots back to firm white tissue with a clean blade. This is the moment to take pups off, since the plant is already out of its pot.
5. Let large cuts dry before planting If you removed a lot of root or cut through the stem, stand the plant in bright shade for a day or two until the cut faces are dry to the touch.
6. Plant at the same depth Set the plant so the point where the lowest leaves meet the stem sits just at the compost surface. Planted deeper, those leaf bases stay damp and rot.
7. Firm lightly and top dress with grit Tap the pot down rather than pressing the compost hard, then add a shallow layer of grit around the base to hold the plant steady and keep the crown dry.
8. No water for seven days Stand it in bright shade and leave it completely dry for a week, then water thoroughly once and return to normal intervals.

Long, bare stems and how to fix them

An older aloe, or one that has spent a long time in poor light, ends up with a length of bare woody stem below the rosette, with the leaves all bunched at the top. This does not correct itself and the plant becomes increasingly unstable.

The fix is to behead and reroot it, which sounds drastic and is actually the standard treatment. Do it in late spring or early summer, at the same time as a repot.

1. Cut the rosette off with a length of stem With a clean sharp knife, cut straight through the bare stem leaving one to two inches (3 to 5 cm) below the lowest leaves. Remove the two or three lowest leaves from that stub.
2. Dry the cut for a full week Stand the cut rosette upright in bright shade, out of any pot, until the cut face is completely dry and corky. A thick stem takes longer than you expect.
3. Pot dry and wait Set it into dry gritty potting mix just deep enough to stand up, in a small pot. Give no water for ten days, then water once. Roots follow in three to six weeks.
4. Keep the old base The stump left in the original pot usually pushes out several pups over the following months. Water it as normal and you get extra plants from the operation.

After repotting, and what to record

The fortnight after a repot is about letting the roots seal and take hold, not about getting the plant growing again. Bright shade, no feeding and no water for the first week, then normal treatment once a new leaf appears from the center.

Write down the date you repotted, the pot size you moved into and the compost mix you used. Aloe needs this so rarely that you will not remember, and knowing that it went into a five inch pot two summers ago is exactly the information you want when it starts overhanging the rim again.