Eradicate Alien Invader Plants


There are many reasons to remove an alien invader and its vegetation from your garden, but how does one go about it? Mechanical or chemical eradication, or a combination of the two, can help a gardener achieve long term success. Biological control is in the hands of the professionals and they have had some success in controlling certain species in natural areas. With some very invasive plants, the whole process can take a number of years before one is finally rid of the plants. As some aliens spread by means wind-dispersed seeds, it is a good idea to check your garden yearly in case a plant sneaks in over the garden wall. Here are some tips on eradication methods:

  • Registered herbicides exist for certain alien plants. Consult your garden centre or seek professional help when using herbicides and follow the directions on the enclosed packet carefully.
  • Some alien plants require just a foliar spray while others will need to be cut down first and herbicide applied to the stump of the plant.
  • Foliar spraying is more effective when the plant is growing vigorously, usually in the summer months.
  • Avoid spraying during hot weather, rain or on windy days.


  • When removing an alien invader by hand, make sure to stamp down the disturbed soil after uprooting.
  • Follow up yearly to get rid of seedlings or regrowth.
  • Don’t put seeding alien plants in the compost heap. Some seeds are able to withstand very high or very cold temperatures for years. Rather take them to a landfill site.
  • Water plants should be collected by hand and can, in most cases, be added to the compost heap.
  • Big trees can be expensive to eradicate. The most expensive part of tree felling is the cartage of cut branches and logs. Some tree fellers will cut down at a decent price if they don’t have to cart. If the stump remains, make sure that a strong herbicide is painted on the cut stump to prevent further regrowth.
  • Strip barking a tree is an option for certain species of tree, but you need to be sure that you use this method only on a tree or trees that are positioned well away from your house or outbuildings, so that they do not collapse onto the buildings when they eventually fall one day. To ‘strip bark’ a tree remove all bark from the tree, beginning one metre above ground level right down to the ground. Dead trees can be left standing to make perches for birds.
  • Plants with underground tubers or horizontal roots are very difficult to eradicate. Make sure that all pieces of root are dug up and check on the area regularly for any regrowth.
  • It is best to wear gloves when eradicating alien invader plants as many of them have thorns, are poisonous or contain compounds which can cause allergic reactions.
The Gardener