We repot a few hundred plants a week at our nursery in Fallbrook, and nearly everything that goes wrong at home comes down to two things: watering right away, and trying to pick the plant up bare handed. Neither one needs special equipment to avoid.
When does a cactus actually need repotting?
Cacti like being snug. A slightly small pot is not an emergency, and there is no calendar for this any more than there is for watering. You repot when the plant tells you to, in one of four ways:
- Roots are pushing out of the drainage hole, or lifting the plant out of its own soil.
- The plant is wider than the pot and tips over if you bump the bench.
- Water runs straight through in two seconds and barely wets anything. More root than soil in there.
- The old soil has broken down into dark dust that stays damp for a week. Peat heavy nursery mixes do this after a couple of years, and it kills a lot of cacti.
Most potted cacti want it every two to four years. A young San Pedro might ask yearly. A slow golden barrel can sit for five and thank you for the neglect.
Timing matters more than people expect. Repot spring through early fall, while the plant is growing and can push fresh roots. One repotted in December sits in new soil with damaged roots and nothing to do until spring.
What do you need before you start?
The repotting kit
- Dry soil, dry plant. Stop watering seven to ten days before. Dry soil crumbles off the roots instead of smearing into them.
- A folded strip of newspaper, three inches wide and long enough to wrap the plant twice. Best cactus handling tool there is, and it is free. Old carpet or a folded blanket for heavy plants, kitchen tongs for small ones.
- Gloves, with realistic expectations. Thick leather stops most spines, but not glochids, the hair fine barbs on prickly pears, which go through leather and then live in the glove forever. Use newspaper on anything in the Opuntia family.
- A gritty, fast draining mix, roughly half grit and half light potting mix.
- A pot with a drainage hole. Not negotiable.
- A chopstick to work soil into the gaps, plus tweezers and duct tape for the spines you will catch.
How do you lift a cactus without getting stabbed?
Small plants, under 6 inches
- Fold newspaper into a band, wrap it around the plant like a belt, cross the ends, and hold them together as a handle.
- Or steady it at the base with kitchen tongs.
- Easiest of all: squeeze a plastic pot and tip the whole thing into newspaper cradled in your other hand.
Big plants, over a foot
- Carpet strip or folded blanket, and two people. A 3 foot columnar in a full pot is heavier than it looks.
- Lay the pot on its side and slide the plant out sideways rather than pulling up.
- Never pull a branching cactus by an arm. It comes off in your hand.
How do you repot a cactus, step by step?
Seven steps
- Let it dry out. Seven to ten days with no water before you begin.
- Prep the new pot. One size up only, about an inch of new space around the plant, two for something large. Skip the gravel layer in the bottom. It raises the wet zone closer to the roots. Cover the hole with mesh.
- Slide it out. Squeeze a plastic pot on all sides, or run a butter knife around the inside of a terracotta one. Tip and slide, do not yank.
- Look at the roots. Healthy cactus roots are firm and tan to off white. Crumble away the old spent soil. If any are black, mushy, or smell sour, cut back to firm tissue with clean snips and let the plant air out two to three days before it goes into soil.
- Set the depth. Back in at exactly the depth it was before, soil line at the same spot on the stem. Planting a cactus deeper than it grew is one of the fastest ways to rot one.
- Backfill dry. Pour dry mix around the root ball, tap the pot to settle it, poke the air pockets closed with the chopstick. Do not pack it hard. A top dressing of pumice keeps the stem base dry.
- Then walk away. No water. Somewhere bright, out of direct midday sun, for about a week while the roots settle.
When should you water after repotting?
Wait. This is the step people skip, and the one that matters most.
The rule never changes: soak and dry, water only when the soil has gone completely dry, never on a schedule. A repot adds one wrinkle. However careful you are, some root hairs tear when you move a plant, and those wounds are wide open. Wet soil plus open wounds equals rot, reliably. So give it five to seven days before the first watering, or ten if you cut roots back. Then water deeply, until it runs out the bottom, and let the soil go bone dry again. Overwatering kills more cacti than everything else combined, and a thirsty cactus bounces back in a day while a rotted one does not. When in doubt, wait.
If the plant already looked off, read why is my cactus turning yellow, brown, or mushy first. A rotting cactus needs the rot cut out, not a bigger pot.
What pot and soil should you use?
Terracotta
- Porous, so soil dries from the sides as well as the top.
- Far more forgiving if you overwater.
- Heavy, which is what you want under a top heavy plant.
Plastic or glazed
- Holds water longer. Fine if your mix is gritty and you are disciplined.
- Light, cheap, easy to squeeze a plant out of.
- A glazed pot with no drainage hole is the worst container you can own. Keep the cactus in a plastic nursery pot and drop that inside.
Bagged potting soil holds far too much water for a cactus. You want roughly half grit: pumice, perlite, or coarse sand. Full breakdown in our guide to the best soil for cactus and succulents.
When should you stop potting up and plant it in the ground?
There is a ceiling. Once a columnar cactus passes three or four feet, a pot big enough to hold it steady is too heavy to move, and you are buying containers to stay ahead of a plant that wants to be in the dirt.
In USDA zone 9 or warmer, most of what we grow can go straight into the ground given sharp drainage and a slope or raised mound. Check your zone, then browse the outdoor landscape cacti. Somewhere colder, keep it potted so it can come inside for winter.
The quick version
- Repot every two to four years, spring through early fall, when roots fill the pot or the plant tips over.
- Let the soil go bone dry for seven to ten days first.
- Lift at the base with a folded newspaper band, never by the top or an arm.
- One pot size up, about an inch of new space, always with a drainage hole.
- Skip the gravel layer in the bottom. It does the opposite of what people think.
- Same depth as before, backfilled with dry gritty mix.
- Wait five to seven days, then water deeply. After that it is soak and dry, forever.
- Duct tape for glochids, tweezers for everything else.