Yucca

Light and exposure

The yucca wants as much light as possible. Place it in front of a south or west-facing window, where it gets direct sun for a good part of the day. It is a full-sun plant: at the back of a dark room it becomes leggy, the leaves pale and the trunk stretches limply towards the light.

In winter, when Belgian light is scarce, move it closer to the brightest pane. A plant going bare at the bottom almost always lacks light above all else.

Watering

This is the point that makes a yucca live or die. It stores water in its trunk and tolerates drought very well, but hates roots sitting in moisture. Water only when the substrate is dry over several centimetres, then always empty the saucer. In full growth, this often comes down to watering every ten to fifteen days.

Excess water is the fatal mistake. A trunk that is soft, spongy or brown at the base signals a rot already established, almost always fatal. When in doubt, do not water: a thirsty yucca recovers in a day, a drowned yucca never.

Soil and repotting

A very free-draining substrate is essential. Mix potting soil for green plants with a third of coarse sand or perlite so the water passes through quickly. Ordinary potting soil that stays waterlogged condemns the plant in the long run.

Repot only every two to three years, in spring, into a barely larger pot always pierced at the bottom. The yucca likes to be a little cramped, and too large a pot keeps too much moisture around the roots.

Temperature and humidity

The yucca is happy between 18 and 24 degrees in the growing season and easily takes the heat of a flat in summer. In winter it appreciates a cooler room, around 10 to 15 degrees, but bright. It tolerates brief spells at 5 degrees, not below: it is a frost-tender plant that never overwinters outdoors here.

Air humidity does not concern it, it comes from a dry climate and does not mind our heated interiors. Just avoid placing it against a scorching radiator, which browns the tips of the leaves. Never leave it outdoors once the nights drop back below 5 degrees.

Pruning and upkeep

The yucca needs little care. Cut off the dry lower leaves that yellow as they appear, this is the plant’s normal ageing, not a disease. Dust the foliage with a damp cloth so it captures the light well.

If it gets too tall, top the trunk cleanly with a saw in spring: the plant will start again by forming new heads just below the cut, and the section serves as a cutting. Turn the pot a quarter turn every two weeks for an even shape.

Pests and diseases

Indoors, the number one enemy remains rot of the trunk and roots, caused by excess water and not by a true pathogen. A trunk soft at the base, a musty smell in the pot: the cause is almost always one watering too many in a poorly drained substrate. It is irreversible once established, only prevention counts.

As for pests, watch for mealybugs, white cottony clusters in the leaf axils, and red spider mites which thrive in the dry air of heating. Clean the mealybugs with cotton soaked in methylated spirit and shower the foliage against red spider mites at the first yellow spots.

Propagation

Trunk cuttings are the prime method. Cut a section of twenty to thirty centimetres, let the cut dry for two or three days to callus over, then plant it in a barely moist free-draining substrate. Roots and new shoots appear within a few weeks in warmth and light.

The offsets at the base of the plant can also be taken: detach them with a few roots and repot them separately. Do these operations in spring or early summer, when the plant is in full sap and heals quickly.

Toxicity

Mildly toxic. The leaves contain saponins that can cause mild digestive upset if a cat or dog chews on them in quantity. Nothing serious in an adult, but it is better placed out of reach of an animal that nibbles at everything.

Month-by-month care calendar

Green Hub tips

• When in doubt, do not water. A yucca takes thirst without flinching but a trunk gone soft from excess water is never saved.
• In winter, a glass of water a month is enough. Continuing to water as in summer is what kills the most indoor yuccas.
• Never leave it outdoors below 5 degrees: this is the frost-tender indoor yucca, not its hardy garden cousin.
• The section you cut when topping makes a perfect cutting. Let the cut dry for two or three days before planting it.