Learn How To Identify Invasive Trees and Bushes

By John Harris, Steward Leader for the Morton Arboretum
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​Common Buckthorn
Rhamnus cathartica

Highlights from the video:

• Usually found in lower areas; does well in wetter places
• The buckthorn is allelopathic, meaning it produces poison in its roots and wood, creating a chemical warfare against its competitors. The toxins discourage other plants, like wildflowers, from growing under and around the tree. The toxins can even affect small mammals, reptiles and amphibians that use the soil.
• Identifying characteristics:
  • Bark has a horizontal feel to the detail on smaller piece; bark has long striations that flake off.
  • Buds are sub-opposite or sub-alternate — not perfectly opposite from one another.
  • Terminal bud is composed of two buds clasping a thorn between them. The shape of this looks like a deer footprint and that is how the tree gets its name "buckthorn".
  • When you peel back the bark the cambium is revealed to have a very orange color. The heartwood is also appears pretty orange.
  • The smell is very distinctive.
  • The leaves emerge early and stay on the tree late into the fall.
  • Berries are black and only found on the female trees. The berries have a laxative effect on birds that helps to spread the tree seeds. For wildlife the berries are not a great food and not favored compared to other choices — a last resort.
  
  
  
  
  
  

Amur Honeysuckle (Bush Honeysuckle)
​Lonicera maackii

Highlights from the video:

• Usually found in light shade in mesic to medium-wet areas. It has taken hold mainly in open woodlands.
• ​In winter it's easy to see that the stems emerge in a fountain shape from the base.
• Identifying characteristics:
  • ​Bark is smooth with striations; older honeysuckle bark looks like a deer antler.
  • Twigs and buds are opposite from each other.
  • Cut a twig and notice it has a hollow pith. A native honeysuckle will have a solid pith.
  • In spring the leaves have a short stem.
  • Buds begin pink and go to white.
  • Red berries in summer. Birds love them, but they don't have the high fat content that the birds really need. Birds spread the seed.
  • Retains its leaves well into the fall.