Plant Doctor Archive

Ailing puka

I HAVE a mature puka that appears to be dying. The one adjacent to it and other surrounding plants are all healthy. We are on the side of a gently sloping hill and drainage doesn't appear to be a problem. I would be grateful of any advice.

IT'S difficult to tell from your photo exactly what the problem is, so here are a few tips to help you investigate further.

Yellowing and drooping of leaves like this is usually the result of the tree's inability to send water and nutrients from the roots up to the leaves. This can be caused in several ways. Root disease is one, but you say the area is relatively free-draining. I wouldn't discount root disease altogether, though, and if none of the other ideas I mention pan out, you could dig in the soil a little way out from the base of the tree and look for healthy or rotten roots.

Collar rot is the next possibility. Look around the base of the trunk and check the condition of the bark - it should look firm and healthy, with no cracks or open wounds. Collar rot can occur if you lay mulch hard up against the trunks of some trees and shrubs. The wet mulch provides an ideal environment for rot-causing diseases to get established in the bark and, if severe enough, they can kill a tree, with symptoms appearing much like those in your photo.

Next, I'd work my way up the trunk and branches looking for open wounds. Believe it or not, pukas can be subject to quite vicious attack by rats. At certain times of year they're attracted to the sweet sugary sap and can chew large holes in stems and branches of quite mature pukas. If enough of the vascular system is destroyed, the tree could exhibit symptoms very much like yours.

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