Gadenin日本語Get the appRepot in spring, every two to three years
Repot every two to three years, in spring, just as the plant comes out of dormancy. Roots trimmed at that time heal quickly and go straight into a season of new growth. Repotting in cold weather or during dormancy leaves damaged roots sitting idle, which often leads to rot.
| Sign | What it means |
|---|---|
| Roots poking out of the drainage hole | Root bound; repot |
| Water sits on top before soaking in | Compacted or worn out mix; repot |
| Three or more years since the last repot | Mix has broken down; repot |
| Newly bought plant in old mix | Repot once spring growth starts |
A gritty, fast draining mix
Because the roots dislike staying wet, use a mix that drains fast and lets air in. A commercial cactus and succulent mix works well. If you blend your own, a mineral heavy mix such as equal parts pumice or perlite, coarse grit, and a cactus potting mix, with a little compost for young plants, gives similar results.
| Ingredient | Approximate share | Purpose |
|---|---|---|
| Pumice or perlite | About one third | Air spaces that resist rot |
| Coarse grit or small lava rock | About one third | Fast drainage and weight |
| Cactus potting mix | About one third | Holds some water and nutrients |
| Compost | A small handful, young plants only | Organic matter for faster early growth |
Seedlings and small plants grow faster in a mix with a bit more organic matter and slightly more water and fertilizer than mature plants get.
Choosing the pot
Go up only one size and always use a pot with a drainage hole. Unglazed terra cotta wicks moisture out through its walls and dries quickly, which suits growers who tend to overwater. Plastic is lighter and dries more slowly, so space waterings further apart.
| Pot type | How fast it dries | Best for |
|---|---|---|
| Terra cotta | Fast | Heavy waterers and humid climates |
| Plastic | Slow | Small plants and dry indoor spots |
| Shallow and wide | Moderate | Showing off a swollen base |
| Deep | Bottom stays wet longer | Tall species such as P. lamerei |
For species with a swollen base, set the plant so the top of the swollen part sits slightly above the mix. It looks better and stays drier at the crown.
Unpotting a spiny plant safely
Most species carry sharp spines. Wear thick gloves or wrap the trunk in a folded band of newspaper and hold the plant through it. Letting the mix dry for a few days beforehand makes the root ball easier to loosen.
- Let the mix dry first Hold off watering for a few days before repotting. Dry mix falls away from the roots more easily and the roots bruise less.
- Wrap the trunk Fold newspaper into a long band, wrap it around the trunk, and grip that. It protects your hands and keeps spines from snapping.
- Tap and slide it out Tap the sides of the pot to loosen the mix, tip the plant, and ease the root ball out. Run a thin spatula around the edge if it sticks.
Trimming roots and replanting
Shake off about a third of the old mix and cut away any black, mushy, or dried out roots, leaving the firm white ones. Do not jump to a much larger pot. Excess mix stays wet and invites rot.
- Remove about a third of the old mix Tease old mix from the outside and bottom of the root ball. There is no need to bare the roots completely.
- Cut out damaged roots With clean scissors, remove roots that are dark and soft or brittle and dead. Keep the plump, pale ones.
- Replant with a little slow release fertilizer Add a layer of coarse grit, then fresh mix with a small amount of slow release fertilizer. Set the plant, fill around it, and settle the mix with a chopstick.
Aftercare while the roots heal
Trimmed roots need time to seal. Watering immediately can start rot at the cut ends, so leave the plant dry for several days to a week in bright shade. Then begin with a light drink and move it back into sun as new growth appears.
- Hold off watering Wait several days to a week before the first watering so the cut roots can dry and callus.
- Rest it in bright shade Keep the plant out of direct sun and rain while it recovers. Strong sun can wilt a plant whose roots are not yet working.
- Ease back into routine care After about a week, give a light drink. When new leaves start to grow, return it to full sun and normal watering.