Article: How to Deal with Invasive Exotics

Created on: Tuesday, September 21, 2004

Invasive and exotic weed species have the ability to thrive in many habitats within their range, thereby threatening indigenous species and the rich diversity of our landscapes.
When dealing with invasives it is wise to have a strategy and be prepared for a long engagement. It is important to take action toward controlling specific plants and seek to modify environmental conditions to favor natives over exotics.

Techniques for Controlling Invasives:
Annuals and Biennials -- most garden weeds -- can be pulled, rototilled, or cut off at the ground just before flowering. Viable seed germination can be arrested by using a pre-emergent herbicide such as Preen®, which forms a barrier on the soil surface that keeps seed from sprouting.
Perennial herbaceous species such as Japanese Knotweed (aka bamboo) are difficult to control. Early eradication is important; consider the use of herbicide (Roundup®)in combination with weeding.
Vines like oriental bittersweet which climb trees can generally be controlled by cutting a segment from the stem and leaving the top growth stranded in the tree canopy. An herbicide applied to the cut stems may minimize sprouting from the base. Hand weeding can also be effective.
Several successive cuttings can be effective in exhausting invasive species. In spring, just after plant has fully emerged from dormancy, completely remove top growth. In summer, after full regrowth, cut completely again. In the fall, repeat the process and remove and discard any flowers. In this way you are hitting the plant repeatedly during its greatest energy demand and eventually it will succumb.
Prior to taking action, assess the impact of any plant removal. Remember to check with your local Conservation Commission regarding regulations pertaining to the Mass. Wetlands Protection Act which affects so many proper ties on Cape Cod. (Its purpose is to protect habitat, water quality and the character of our waterfront and abutting lands.) Discontinue activities such as clearing and fertilizing that encourage invasive exotics. Initiate the regeneration of indigenous species. Make every effort to avoid the use of herbicide, confining its application only to the most intractable species. Herbicide use should diminish over time on each site as initial control is accomplished and more desirable plant communities become established. Persistence and patience, not weaponry, are the keys to controlling invasive plants.
If we want to restore the ecosystems we depend upon, we cannot plant species that have demonstrated themselves to be successful invaders at the expense of native habitats. Plantings in and adjacent to natural areas should be confined to locally native species. Pine Tree Nursery offers native inkberry holly, shadbush, clethra (summer sweet), fragrant native azaeleas, viburnums and dogwoods, bayberry, beachplum, and highbush blueberry, as well as native grasses and flowers for your natural garden.

Excerpted from The Once and Future Forest by Leslie Jones Saur