Repotting

Repotting is one of the few times you get to look a succulent in the roots, and for cacti and other succulents it is as much a health inspection as a housekeeping job. Fresh roots want fresh, gritty, open mix; tired soil slumps into an airless sludge that holds water against the plant and invites rot. Because these plants store their own water in swollen bodies, leaves and roots, they can coast for a long time in a bad pot before they suddenly collapse — so periodic repotting, done at the right season and followed by a strict dry rest, is cheap insurance against a slow, hidden decline.

When and why to repot

Succulents do not need repotting on a fixed calendar the way fast, thirsty houseplants do. Repot when the plant tells you to, or when you have a reason to look:

Rootbound. Roots spiralling the pot wall, poking from the drainage holes, or lifting the plant out of its own soil. A snug pot is fine — even desirable — but a solid root mass with no soil left cannot hold moisture or feed the plant.
Tired, broken-down mix. Old mix loses its structure: the organic fraction rots to a dense paste, mineral grit settles, and the surface no longer dries between soakings. If water sits on top or the pot stays heavy for days, the mix is spent.
After purchase. Nursery plants very often arrive in a peaty, water-retentive mix meant for shop-shelf convenience, not long-term life on your bench. Repotting a new Astrophytum, Ariocarpus, Lithops or Echeveria into your own gritty blend is one of the best things you can do for it — and lets you check for pests like mealybug in the roots.
Rot check or rescue. If a plant looks off — a soft base, a wobble, a sour smell — get it out of the pot and inspect. Catching brown, mushy root or a rotten neck early is the difference between a trimmed cutting and a compost casualty. See Rot and rescue.

Best timing: the start of the growing season

Repot when the plant is waking up and ready to push new roots, so damaged roots heal fast and the plant re-establishes quickly. For most cacti and warm-growing succulents that means early in the growing season — spring, as growth resumes — not the depths of dormancy.

The catch is that succulents keep two different calendars. Summer growers (most cacti, Echeveria, Aloe, Trichocereus) are best repotted in spring. Winter growers such as Lithops and other mesembs, and many Haworthia and Aeonium, move into growth as the weather cools, so their ideal window is early autumn instead. The principle is the same for both: disturb the roots as the plant heads into active growth, never as it heads into rest. Avoid repotting a plant in deep dormancy or in peak summer heat, when cut roots sit idle and are far more likely to rot than heal.

Handling spiny plants safely

The practical obstacle to repotting cacti is that they bite. A few simple tools let you keep a firm grip without crushing the plant or filling your hands with glochids:

Folded newspaper collar. Fold a strip of newspaper several layers thick into a band, wrap it around the plant's waist like a belt, and hold the two ends together as a handle. This spreads the pressure over a wide area so you are not levering on a few spines, and it works for anything from a small Mammillaria to a hefty barrel.
Hose or rope loop. For big Ferocactus or columnar Trichocereus, a loop of old garden hose or thick rope cradled around the body gives two lifting handles and keeps your hands well clear.
Tongs and gloves. Kitchen or barbecue tongs handle smaller plants; thick gloves help but will not stop long, stiff spines, and they are almost useless against the fine, barbed glochids of Opuntia — those work into skin and gloves alike, so lead with the newspaper method rather than bare hands.

Grip the body, not the growing tip, support the weight from below, and move slowly. A snapped spine cluster or a cracked growing point is a permanent scar on a slow-growing plant.

Bare-rooting, inspecting and trimming roots

Once the plant is out, gently tease away the old mix so you can see what you are dealing with. Crumbly, spent soil often falls away on its own; for a stubborn root ball, working dry is easiest — the old mix should be bone dry at repotting time anyway.

Inspect. Healthy roots are firm and pale. Look for the enemies: mushy brown or black root (rot), white cottony patches or waxy specks in the root zone (root mealybug), or a whole root system that has simply died back and gone papery.
Trim. It is normal and healthy to prune roots at repotting. Cut away dead, black or shrivelled roots with a clean, sharp blade, and shorten an overgrown mass so it sits comfortably in the new pot. Many growers deliberately trim back fine feeder roots to encourage a compact, vigorous flush of new ones; a fat taproot, by contrast, is a storage organ — spare it where you can and only pare a damaged one back to clean flesh.
Treat damaged roots. Where you have cut into live tissue — especially removing rot — pare back to clean, firm flesh, dust the wounds with sulphur or a fungicidal powder if you have it, and then let the plant sit dry and unpotted for several days so every cut surface calluses over before it ever touches soil. Potting a fresh wound straight into mix is the classic way to turn a small rot into a fatal one.

Sterilise your blade between plants so you are not carrying rot or pests down the bench.

The dry settling-in period

This is the step most people get wrong, and it is the most important one on the whole page. Do not water a freshly repotted succulent. Repot into dry mix, place the plant, and then leave it dry for several days to about a week — longer for anything whose roots you cut hard, and longer again for large-bodied cacti.

The reason is specific to how these plants work. Repotting always nicks and breaks roots, and those open wounds are wide-open doors for rot. In moist soil they infect; in dry soil they callus. A water-storing succulent has plenty of internal reserves to coast through a dry week with no stress at all — it will not miss the water, but it will very much mind the rot. Give the roots time to seal, keep the plant out of blazing direct sun while it settles, and only then give the first cautious watering to invite new roots out into the fresh mix. From there, resume your normal soak-and-dry rhythm.

Pot size and material

Resist the urge to "pot up" into something much bigger. A pot only a little larger than the root ball is right for almost every succulent.

Size — snug, not oversized. A big pot holds a big volume of mix that stays wet long after the roots have drunk their fill, and that lingering moisture is exactly what causes rot. A snug pot dries out quickly and evenly. Deep, narrow pots suit taprooted plants like Ariocarpus, Lophophora and many caudiciforms — and, less obviously, Lithops, whose fat contractile taproot wants more depth than their squat bodies suggest; shallow pans suit clumping, fine-rooted rosettes like small Haworthia.
Material. Unglazed terracotta breathes and wicks moisture, so the mix dries faster — a real safety margin for heavy-handed waterers and in humid climates, at the cost of more frequent watering. Plastic and glazed ceramic hold moisture longer, which suits fine-rooted plants and drier growing conditions but is less forgiving of overwatering. Whatever you choose, it must have a generous drainage hole. A pot with no hole is a death trap for a succulent, however pretty.

Top-dressing

A layer of coarse mineral grit — pumice, lava, coarse sand or fine gravel — spread over the surface after potting is more than decoration. It keeps the vulnerable neck and lower body of the plant off wet soil, which markedly cuts rot at the point where cacti most often go soft. It stops fine mix splashing up onto the plant and spines when you water, discourages moss and fungus gnats on the surface, and helps the mix dry evenly from the top. Choose a top-dressing whose particle size roughly matches your mix so it does not simply sift down into it.

How it differs by group

Group	Best timing	Pot & handling notes
Globular & columnar cacti (Astrophytum, Mammillaria, Trichocereus)	Spring, as growth resumes	Newspaper collar or hose loop to handle spines; snug pot; heavy top-dressing at the neck; long dry rest before first water.
Leaf succulents (Echeveria, Aloe, Haworthia)	Spring (autumn for winter-growing haworthias)	Easy to handle bare-handed; support the rosette from below so leaves don't snap; snug pot dries fast.
Lithops & other mesembs	Early autumn, as they wake	Disturb roots as little as possible; a deeper pot than the squat body suggests, to take the taproot; very gritty mix; keep bone dry for a good while afterwards — mesembs rot at the slightest excess.
Caudiciforms & taprooted plants (Ariocarpus, caudex growers)	Start of their growing season	Deep pot for the taproot; decide how high to set the caudex; treat cut taproots and callus thoroughly before potting.
Epiphytic cacti (Rhipsalis, Schlumbergera)	After flowering, as new growth starts	Prefer a more organic, bark-based mix and a snug pot; brittle segments break easily, so handle the whole plant, not individual stems.