Suckering Robinia

The Golden Robinia (Robinia pseudoacacia 'Frisia') was a vogue tree in Australian gardens and landscapes during the 1980s and is still popular today. It is widely used as a street tree, particularly in polluted areas and, because of its small size and pretty colouring, was often recommended as a tree for suburban gardens. Similarly the Mop Top Robinia (Robinia pseudoacacia 'Umbraculifera') is a popular garden tree because of its jade green foliage and attractive shape.

Suckers

These attractive and useful small trees do have one important drawback: they are prone to suckering. This happens because the variety is grafted on to a vigorous understock, R. pseudoacacia, also known as the False Acacia. The False Acacia will grow to 20m (60') and is native to the United States. It is a deciduous tree with green compound leaves and sharp thorns and it is now naturalised in many parts of Europe, Asia and Australia.

If its roots are damaged (for example by a mower or whipper snipper or by digging) or if the roots hit an obstacle, such as a clay soil, they will produce suckers. This characteristic is retained when the tree is used as an understock.

In the case of the Golden Robinia 'Frisia' and the Mop Top Robinia the suckers are not yellow but green and thorny as they are from the understock. Because the suckers can grow up to 17m (56') from the base of the original tree, particularly in clay soil areas, they can be a nuisance in a small garden. If they emerge around house foundations it is best they are removed whilst young.

Controlling suckers

Suckers are very difficult to control once they start appearing. They should be cut off with a clean sharp cut as close as possible to the root.

Care should be taken when mowing or gardening around any grafted plant (but particularly robinias) not to damage the root system. If possible, mulch under these trees rather than grow grass, as repeated mowing does seem to lead to suckering.

If the suckers come from a tree that has died they can be painted with the herbicide Roundup. This will kill the suckers but, if still attached to a living tree, would possibly kill the tree as well. Left untreated the suckers will grow vigorously into large thorny specimens of the False Acacia.

Further information

The Golden Robinia, Mop Top Robinia and other ornamental forms of Robinia are attractive, small trees for warm to cool areas (Brisbane to Perth and south and mountain areas) but their suckering habit needs to be considered if these trees are chosen for a small garden. Plants are available in most nurseries throughout Australia.

Copyright CTC Productions 2006