Kalanchoe

Light and exposure

The kalanchoe demands a huge amount of light. It is the plant that flowers best in direct sun: give it the brightest windowsill in the house, facing due south if possible. Without strong light it lives perfectly well but stays green and refuses to flower again, which is often a disappointment.

In the Belgian winter, light is weak and short, and that is the real limiting factor. Move the pot close to a south-facing window and do not be afraid of the direct sun of the dreary season, which does not scorch the plant at that time of year. In summer, full sun behind a window heats up strongly: there, a light net curtain during the hottest hours prevents the foliage from reddening or getting marked.

Watering

This is where most kalanchoes are killed. Like any succulent, it stores water in its leaves and hates excess. Water only when the substrate is thoroughly dry over several centimetres, then soak generously and let the water drain away. In winter this may mean once every two to three weeks, no more.

Never let water sit in the saucer. Roots left permanently soaking rot the collar and the roots, the number one mistake with succulents here, and the plant goes soft from the bottom before it collapses. Water at the base, not on the leaves or the flowers, and when in doubt wait an extra day: a kalanchoe copes far better with thirst than with excess.

Soil and repotting

The kalanchoe wants a very free-draining substrate. A special mix for cacti and succulents suits it perfectly, or a good potting soil lightened with a third of coarse sand or perlite. Water must pass through quickly and never linger.

Repot in spring, after flowering, into a pot barely larger and above all with a hole in the bottom. A layer of clay pebbles or gravel at the bottom improves drainage further. A terracotta pot, which lets the root ball breathe, is a good choice for a plant that dreads stagnant moisture.

Temperature and humidity

The kalanchoe is happy between 15 and 25 degrees, exactly the temperatures of a Belgian home, which makes it a very easy-going houseplant. It tolerates a little coolness at night but stops growing below 10 degrees.

The critical point is frost: this plant is frost-tender, it blackens and dies as soon as the thermometer approaches zero. Never put it out on an outside ledge or the terrace from October to May, and beware of the leaves touching an icy pane directly on winter nights. As for humidity, no problem: it prefers the dry air of our heated homes to a damp atmosphere, so there is no need to mist it.

Pruning and upkeep

Routine care comes down to very little. Cut the faded flower stems back to their base once flowering is over: this cleans up the plant and encourages it to start again. Pinch the tips of the stems from time to time to keep a compact, stocky shape, otherwise the kalanchoe stretches out and goes bare at the bottom over the years.

Remove the soft or dried leaves from the base as they appear. An old plant that has sprawled can be cut back hard in spring: it recovers well, and the cut pieces will serve as cuttings. Dust the fleshy leaves with a dry cloth now and then so they capture the light well.

Pests and diseases

Indoors, the kalanchoe is rarely sick, but excess water remains its enemy. Collar and root rot, encouraged by a waterlogged substrate and the damp air of our winters, shows up as a base that browns and softens. At that stage you save the plant by taking an emergency cutting from a healthy head. Powdery mildew, a white felting on the leaves, can appear in a damp, poorly ventilated room.

As for pests, watch out for mealybugs, those little white cottony clusters in the leaf axils, common on indoor succulents: you remove them with a cotton bud soaked in methylated spirit. Aphids sometimes attack the tender flower buds. Sticky or spotted foliage is the signal to watch closely.

Propagation

The kalanchoe multiplies very easily, a real pleasure. The stem cutting is the quickest: cut a ten-centimetre piece, remove the bottom leaves, let the cut dry in the air for a day or two so it heals over, then plant in a barely moist free-draining substrate. Roots come in two to three weeks.

The leaf cutting works too: lay a fleshy leaf flat on potting soil, and a little plantlet eventually forms at its base. Take these cuttings in spring or summer, when light and warmth drive recovery. It is the simple way to renew a tired old plant without buying anything.

Toxicity

Toxic to cats and dogs. The whole plant contains bufadienolides, molecules that act on the heart. An animal that eats some may show vomiting, drooling, diarrhoea, and in serious cases heart rhythm disorders. Keep it out of reach of animals and young children.

Month-by-month care calendar

Green Hub tips

• To reflower a kalanchoe, give it fourteen hours of pitch-dark night a day for six weeks from the end of September. Without this darkness it stays green and makes no buds.
• When in doubt, do not water. This succulent dies of excess water, never of thirst. Wait until the substrate is dry over several centimetres.
• Never put it outdoors in Belgium, even in summer on the terrace: the slightest cold autumn night kills it. It is an indoor plant all year round.
• Keep it out of reach of cats and dogs: its leaves and flowers are toxic to them and can affect the heart.