Roebling Park - Island Trail
Garlic mustard is a biennial plant that flowers and sets seed in spring of its second year. As a biennial it has a weak root structure and can be easily pulled from the ground. It is important to pull the garlic mustard before it flowers in the spring if vegetation is to be left on the ground. Once garlic mustard flowers, it is advisable to bag and remove the plants after pulling them to avoid the spread of seeds.
Japanese knotweed represents a significant potential threat to Island vegetation and efforts should be made each year to keep the population under control. Mechanical cutting alone of japanese knotweed is not considered to be optimum for long term management, but it may be the only available option. Annual plans for the removal of japanese knotweed should always be coordinated with the Mercer County Park Stewardship Staff. Japanese knotweed can be cut at the base of the cane at specific intervals throughout the growing season.
Mile-a-minute vine is an annual that is easily pulled out of the ground by hand. Mid-summer is a good time to remove the vine, before it flowers and goes to seed. At the present time Mile-a-Minute is concentrated along the Center Trail on the Island as indicated on the Invasives Map. Any new populations discovered should be reported.
Japanese honeysuckle and oriental bittersweet are present in many places on the island in sufficient numbers to make total elimination impractical. However, in instances where the honeysuckle or bittersweet vines are climbing native trees it is well worth the effort to cut the vines to prevent damage to the tree. This is especially true of saplings and young trees. Vines can be cut at any time of year, but winter and early spring are generally the most convenient times to easily access them. Porcelain berry is also present in some areas of the Island.
Occasional invasive shrubs found on the Island include: autumn olive, burning bush, linden viburnum, and japanese barberry. The recommendation for controlling these shrubs is to combine cutting of the shrub with dabbing the cut stump with an appropriate herbicide. This method requires coordination with a licensed herbicide applicator. If this coordination is not an option, it may be beneficial to cut the invasive shrub near the base without herbicide treatment. This is likely only a temporary solution.
Mugwort and multiflora rose are both examples of invasives that are very difficult to eradicate once they have become established in an area. The stewardship emphasis for these invasive plants should be to be on the lookout for new and/or small populations occurring in an otherwise un-invaded area. In these instances, mugwort can be pulled out by the roots and multiflora rose can be cut back to ground level and/or removed from native trees.