Plant Doctor Archive

Brown spots on yucca

MY yucca had grown too large for the lounge, so about a year ago I planted it outside. But within a month or two brown spots appeared, increasing with time. Now all the new leaves soon turn brown at the tips with spots all over the rest of the plant. There are always a lot of spiders and webs on the plant, but no sooner do I clear them away than they come back.

IT looks like your yucca is suffering from a combination of cold temperatures and poor drainage. They grow best in warm, relatively dry conditions and need free-draining soil. The cold winter nights you can get in your area are probably pretty close to the limit yuccas can endure, but the fact that it's already survived one winter shows how tough yuccas are for a plant that grows best in the sub-tropics.

If you can transplant it to a more sheltered spot in the garden, say, close to nearby trees where it will be better protected from frost but where it still gets plenty of sun, then the colour and growth will probably improve. And rather than plant it directly into the soil, build up a mound of bark or growing mix from the garden centre, about 50cm high by a metre across, and plant in that so the root system is above the surrounding soil level. This will improve drainage and the growing mix will also stay warmer and so encourage a healthy root system.

In winter you could cover the plant with a couple of layers of frost cloth for extra protection on those clear nights when the temperature really drops. The spiders won't do any harm, their webs just look unsightly.

Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.