How often should I water succulents and cacti?

Light

Most succulents and cacti need a lot of light indoors, and a sunny south- or west-facing windowsill suits many of them. In too little light they stretch towards the glass, lose their colour and grow pale and leggy, and they use so little water that rot becomes likely. In a bright window in summer, the calculator suggests every 11–22 days.

Pot and soil

Use a gritty cactus compost, or ordinary compost mixed half and half with grit or perlite, in a terracotta pot with a drainage hole. A pot without drainage is a common way to lose a succulent. Soak it until water runs from the base, then wait until the soil is dry all the way through.

Through the year

In medium light the calculator starts at every 14–28 days in spring and summer, 18–36 in autumn and 22–45 in winter, stretching to 29–58 days in low light in winter. Many cacti flower better after a cool, almost dry winter rest. The wide range reflects how varied the group is: a small pot of sedum dries out far sooner than a large barrel cactus.

Too much or too little

Thirst shows as leaves that wrinkle, thin and lose their plumpness, or a cactus that shrinks and puckers; it recovers within days of a soak. Overwatering is far harder to undo: leaves turn translucent, yellow or black and drop at a touch, and stems go soft and dark from the base upwards. Cut healthy pieces off a rotting plant, let them callus, then root them in dry grit.