Plant Doctor Archive

Spiky citrus

SEVERAL of my 2-year-old citrus trees show spiky growth that is dark green and comes from the base of the stem. Some plants still have their original stem growing, but with others it has died off. The site is quite windy with occasional moderate frost. Should I do anything or just let them grow out?

THE spiky shoots are suckers growing from the rootstock. Most citrus varieties in this country are grafted on to a root-stock, Poncirus trifoliata, often called simply trifoliata. It tolerates our cold, wet winter conditions so we can grow a wide range of citrus fruits which would otherwise need more tropical conditions to crop well.

Trifoliata has long thorns and each leaf has three distinctive leaflets - hence the name trifoliata. It sounds as if your young trees have suffered from stress of some kind, perhaps lack of water or lemon tree borer, which has stimulated the rootstock to send up shoots from below the graft.

Those trees where the original branches have died need to be replaced - they won't recover. With the others you need to remove the suckers as soon as possible to force all growth into the desirable fruiting parts of the tree. Cut the suckers, or pull them off as close to the main stem as possible.

If they're small enough, break them off with a downward pull, but take care not to tear away a large strip of bark. If they're growing from below ground, scrape away the soil so you can remove as much of the sucker as possible. Be alert for more suckers from the same area in the future and remove them while small.

To reduce the chances of it happening again buy the healthiest looking plants you can, keep them well watered during dry periods for at least the first couple of years and fertilise in spring and autumn. Remove all fruit as it forms for the first couple of seasons to reduce stress on the young tree and to encourage strong branch growth.

It's worth noting 'Meyer' lemons are often grown from cuttings as they do quite well on their own roots in most areas. So if your garden centre can sell you a cutting-grown 'Meyer', you'll have no problem with suckers.

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