Cacti have a reputation as the ultimate no-care plant — buy one, ignore it forever. Indoors, that reputation gets people into trouble, because "ignore it" and "water it like a normal houseplant" are both wrong. A cactus is a desert plant with two firm demands: lots of light and very little water. Meet those (plus a cool winter rest if you want flowers) and a cactus really is nearly carefree — and can surprise you with spectacular blooms.
#Meet the cactus
Cacti are succulents adapted to hot, sunny, arid environments, storing water in their thick, often spiny stems to survive long droughts. That single fact drives everything: they want strong light, fast-draining soil, and to be bone dry most of the time. Treating a cactus like a leafy tropical — regular water, rich moist soil — is what kills them.
#Light: lots of it
Cacti are among the most sun-loving houseplants:
- Best: your brightest spot — a south- or west-facing window with several hours of direct sun.
- Too little light causes etiolation: the cactus stretches tall and thin, pale and weak, reaching for the sun.
Etiolated growth won't reverse, but more light keeps new growth normal. If you lack a bright window, a grow light keeps cacti compact. Introduce a cactus to intense sun gradually to avoid scorching.
#Watering: the "soak and forget" method
This is where cacti live or die. They need very little water, and even less than you think:
- Water thoroughly only when the soil is completely dry, then wait until it's bone dry again — often every 2–3 weeks in spring and summer.
- In winter, water very little or not at all (see the dormancy section) — this is essential and where most people go wrong.
- Never leave a cactus in standing water.
Overwatering causes soft, mushy, browning tissue, especially at the base — the start of fatal rot. When in doubt, don't water. A slightly shrivelled cactus recovers with a drink; a rotting one usually doesn't. See indoor succulent care, which shares the same principles.
#Soil and pots
Cacti need a gritty, extremely fast-draining mix — a cactus/succulent blend, or potting soil cut heavily with coarse sand, perlite, or pumice. See potting soil. A pot with drainage holes is non-negotiable — those cute hole-less pots are cactus death traps. Terracotta is ideal, wicking moisture and drying the soil fast. When handling spiny cacti to repot, wrap them in folded newspaper or wear thick gloves.
#The cool winter rest (for flowers)
Here's the secret most people miss: many cacti need a cool, dry winter dormancy to bloom. To encourage flowers:
- Through winter, keep the cactus cool (around 10–15°C) and nearly dry — barely any water.
- Give it bright light still.
- In spring, gradually resume light watering as growth restarts.
This cool, dry rest mimics its natural cycle and triggers spring flowering. Without it, plenty of cacti simply stay green and bloomless — well cared for, but never flowering.
#Feeding
Feed lightly — a diluted cactus/succulent fertiliser once or twice during the spring–summer growing season is plenty. Don't feed in winter dormancy. See fertilising.
#Common problems
Soft, mushy, brown base. Rot from overwatering/poor drainage. Cut away rot, dry, repot gritty, water far less.
Tall, thin, pale growth. Etiolation from too little light. Move to the brightest spot or add a grow light.
Shrivelled, wrinkled stem. Underwatering (rare) — a thorough soak should plump it. If the soil is wet, suspect root rot instead.
No flowers. Usually no cool, dry winter rest — or not enough light or maturity.
Corky brown patches with age. Natural corking on older cacti — usually normal, not rot (rot is soft; corking is firm).
#The bottom line
A cactus indoors isn't a set-and-forget rock — it's a desert plant with clear needs. Give it your brightest light, plant it in gritty soil with drainage, water it thoroughly but rarely (and almost never in winter), and give it a cool, dry winter rest if you want blooms. Do that, and your cactus stays firm, green, and compact for years — and one spring, it just might reward your restraint with a flower worth the wait.