Plant Doctor Archive

Yellowing leaves on cycad

THE leaves on my potted cycad are turning yellow. It's growing in full sun and gets adequate water. Does it need feeding or repotting?

THERE are several reasons why cycad leaves turn yellow. Check the undersides and stems for scale or mealybug. If they are present, spray with Confidor, Rogor 100 or Target. Avoid using spraying oil as it can damage palm foliage and I suspect it may also harm cycads.

It could be that the mix has run out of nutrients, so feed with a slow-release fertiliser such as Osmocote or Nutricote. Follow the label directions and don't overdo it. Alternatively, repot the plant into a larger container with fresh mix.

Check the roots, too. You may find mealybug there as well. If so, after repotting drench the mix with a solution of the same spray. Or you may find some roots are rotten. Trim off any dead roots, ensure the container is free draining and repot into a fresh mix. Reduce the watering frequency - only water when the surface of the mix has dried out. To help prevent further rot you could drench the mix after repotting with No Root-Rot, a fungicide for treating root diseases. It's available in some garden centres.

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