Gadenin日本語Get the appRepot while it is growing
Repotting breaks roots, and the plant has to replace them, which only happens while it is actively growing in a warm room. Spring is the best time by a clear margin, and early summer is a good second. Avoid it altogether from mid autumn onwards, when cut root surfaces sit wet and rot instead of healing.
Most spider plants want repotting every one to two years. The plant is unusual in how strongly it fills a pot: the white storage roots swell until they lift the whole rootball above the rim and, in a rigid plastic pot, can crack it.
| Season | Repot? | Why |
|---|---|---|
| Spring | Best | Warmth rising, roots replaced within weeks |
| Summer | Yes, with care afterwards | It transpires hard, so keep it out of sun after |
| Early autumn | Only at the very start | Just enough time to root before the cold |
| Late autumn to winter | Avoid | Roots barely move and cut surfaces rot |
Signs it needs a bigger pot
Work from what the plant is doing rather than from a schedule. Any two of these together mean it is time.
- The rootball is pushing upward The compost surface rises above the rim, or the whole plant sits noticeably higher than it did. Thick roots swelling underneath are lifting it, and there is nowhere else for them to go.
- It dries out in a day or two A pot that is almost entirely root holds almost no water. Needing water every other day in summer is a repotting signal rather than a watering problem.
- Roots out of the drainage holes White roots pushing through the bottom, or a rootball that lifts out as one solid block with no loose compost, mean the pot is full.
- Growth has stalled Feeding and light are fine but no new leaves are coming and no plantlets appear. A completely pot bound plant eventually stops rather than flowering.
Being slightly pot bound is what encourages plantlets, so do not repot a plant that is producing runners happily and still growing. Only move it once the signs above appear.
One size up, and mind the crown
Move into a pot one to two inches (3 to 5 cm) wider than the current one, no more. A much larger pot leaves a mass of compost with no roots in it, and that compost stays wet, which is the commonest cause of rot in a plant that was previously healthy.
| Current pot | Next pot | Plant spread |
|---|---|---|
| 4 in (10 cm) | 5 to 6 in (13 to 15 cm) | Up to 10 in (25 cm) |
| 6 in (15 cm) | 7 to 8 in (18 to 20 cm) | 10 to 18 in (25 to 45 cm) |
| 8 in (20 cm) | 10 in (25 cm) | 18 to 28 in (45 to 70 cm) |
| 10 in (25 cm) and up | Same size, divide instead | When you do not want it larger |
Set the plant so the crown, where the leaves emerge, sits at the same depth as before and level with the compost surface. Burying the crown even half an inch is the fastest way to rot the center of the plant.
Compost and pot choice
The roots are thick and want air around them, so build the mix for drainage rather than for water holding. Roughly three parts houseplant compost to one part perlite or coarse grit is right for most homes, and more perlite again if your room is cool or you tend to water generously.
- Use a pot with drainage holes There is no version of this plant that succeeds in a sealed container. If you like a decorative outer pot, keep the plant in a plain inner pot and lift it out to water.
- Terracotta suits a heavy waterer It breathes and dries faster, which forgives overwatering. Plastic suits a cool room or a hanging position where you cannot water often, but the swelling roots can split it.
- Do not reuse old compost as it is Old compost has collapsed, drains badly and is loaded with salts. Replace at least half of it with fresh, and shake the worst of it out of the roots.
Doing it, and the fortnight afterwards
Water the plant the day before so the rootball holds together, then slide it out and tease the outer roots loose with your fingers. Cut away anything brown, soft or hollow with clean scissors, and shorten any root that has spiralled round the base of the pot.
- Fill in and settle without ramming Work fresh compost in around the sides and tap the pot down to settle it. Pressing hard destroys the air spaces the roots need, so let watering do the settling.
- Water once, then leave it Water thoroughly until it runs out, drain it, and keep the compost only just damp for the following fortnight while the cut roots heal.
- Keep it out of strong light Stand it somewhere bright but sheltered for two weeks. Full sun on a plant with damaged roots causes wilting it cannot recover from quickly.
- Do not feed for a month Fresh compost holds enough, and fertilizer on freshly cut roots burns them. Note the repotting date so you know when feeding can restart.
Never repot and divide on the same day, and never repot and cut back hard on the same day either. One operation at a time gives the plant something intact to recover with.
Holding it at the same size
If the plant is where you want it and the pot is as large as you want, you do not have to keep going up. Take it out each spring, shave a third off the outside and bottom of the rootball with a clean knife, and return it to the same pot with fresh compost.
Divide instead when even that stops working, or when the clump has become so dense that the middle leaves yellow from lack of light and air. Two smaller plants in good condition are worth more than one congested one.