How to care for an indoor plant

Nearly every houseplant that dies does so for one of four reasons, and 90% of the time the reason is the same: too much water. Here they are in their real order of importance.

1. Light — decide it before you buy

It is the only thing you can't fix later. Look at where the plant is going to live before you choose it:

• Next to a large window, no direct sun: almost anything works.
• Two or three meters (7 to 10 ft) from the window: pothos, snake plant, ZZ plant, ferns, calathea.
• A corner with no window: nothing truly lives there. If you insist, a snake plant or a ZZ plant, and rotate it to a bright spot every two weeks.
• Direct midday sun: cacti and succulents only. Anything else gets its leaves scorched.

A trick to measure it: hold your hand over the pot at midday. If it casts a sharp shadow, the light is good. If the shadow is fuzzy, it's medium light. If there's no shadow, there's no light.

2. Watering — the universal mistake

Don't water by the calendar. Water when the plant asks for it.

The finger test: push a finger two or three centimeters (about an inch) into the soil. If it comes out dry, water. If it comes out damp, wait. It's more reliable than any rule.

When you water, water thoroughly: until water runs out of the holes at the bottom. Then empty the saucer. Ten minutes with the pot sitting in water is already enough to start rotting roots. A deep, infrequent watering is far better than a daily splash.

3. The pot

It has to have a drainage hole. No exceptions. Those closed decorative pots sold in home-decor stores kill plants: if you like one, use it as a cachepot and leave the plant inside in its plastic pot with holes.

And don't oversize it: a pot that's too big holds moisture the roots can't reach. When you repot, go up one size, not three.

4. The potting mix

Garden soil doesn't work in a pot: it compacts and doesn't drain. Use an indoor potting mix, and if the plant is one that hates excess water, mix in a handful of perlite or coarse sand.

What isn't urgent

Fertilizing every 15 or 20 days in spring and summer is enough. In fall and winter, none at all: the plant is dormant and the fertilizer builds up and burns the roots. Wiping the dust off the leaves with a damp cloth once a month helps more than you'd think — that's how it breathes.

If something goes wrong

The leaves warn you before the plant is lost. The diagnostic guide is in why leaves turn yellow. And if you're a beginner, start with the plants that are almost impossible to kill.