Invasive plants are hard on your trees. There’s no doubt about it.

And in my opinion, bush honeysuckle poses one of the greatest threats to our Illinois woodlands and woodlots. A very helpful feature for identifying this plant is that it tends to hang on to its dark green leaves well into early winter, and along with orange berries, it stands out compared to the bare branches and limbs of other shrubs and trees. Look for bright red and orange berries usually in pairs of fours, light tan bark that looks stringy, opposite leaf arrangement on twigs, and stems with a hollow pith or center.

Oriental bittersweet is another woody vine that can also significantly take over trees. In contrast to bush honeysuckle, oriental bittersweet drops its lime-green/yellow leaves fairly early in fall. Its bright red berries are encapsulated in an orange-yellow capsule that peels back and may remain on female plants well into winter. Unfortunately, oriental bittersweet is a popular fall and winter decoration, and folks like to use it in holiday arrangements.

Identification is important because native bittersweet is not an invasive and can be found with oriental bittersweet. How to tell them apart? Check out the berries. Oriental bittersweet has berries along the stems in the axils, while native bittersweet berries are on the end of the branches. Additionally, the bark of oriental bittersweet is a light gray with diamond-shaped lenticels, or breathing pores, and the bark becomes flaky as it ages.

How to manage invasive species

Like any invasive plant management approach, prevention and application of control measures early on are very important before the plant can get established. Fall and winter is a good time to control these plants using either a cut-stump or basal bark herbicide application.

Cut-stump treatments involve cutting the plant down to the ground to about 6 inches, and then treating the cut surface with herbicide. For stems less than 2 inches across, treat the entire cut surface to the point of runoff. When treating larger stems, you only need to treat the outer 1 inch of cut surface. Add a dye to your spray mix to help track the stumps you’ve treated.

You will need to treat all the cut surfaces of multi-stemmed plants. Basal bark sprays usually require more herbicide, but are usually quicker to apply. If you use the basal bark method and plants leaf out the following spring, do not panic! In most cases, the leaves wilt shortly thereafter, and the plant will die. If some survive, be prepared to retreat.

A major advantage of using these methods is that the prescribed herbicides work on a variety of woody invasive species, which means less remixing, less herbicide handling and less application equipment.

For non-chemical control, prescribed fire may kill seedlings, but must be combined with integrated control methods to prevent re-suckering. Grubbing out young honeysuckle plants may also help.

As always, before applying any herbicide, be sure to read the entire label for information on treatment rates, proper personal protective equipment, method of application, proper storage and disposal, and any environmental restrictions or warnings.

Be persistent in your management efforts. Invasives will not just disappear after one treatment effort. It may take three to five years to really clean things up. That is why it is important to be aggressive upfront before they get out of hand.

For information on invasive plants and management, consult your local Extension office.              

Miller is a horticulture professor at Joliet Junior College in Joliet, Ill., and a senior research scientist in entomology at The Morton Arboretum in Lisle, Ill. Email your tree questions to him at [email protected]. The opinions of this writer are not necessarily those of Farm Progress/Informa.