While the summer is winding down, annual weeds have not yet disappeared and may be at their largest yet. At this point the best method for removal will have to be determined on a site-by-site basis, there are several available options and your arborist can help narrow it down. Newly planted areas may be the most susceptible to weed invasion, check new installations of trees and shrubs as weeds may have hitched a ride on the root ball, especially field grown specimens planted earlier this season or even last year. Some of the most commonly found offenders at this time of year are pictured below:
Horsenettle, Solanum carolinense, is an introduced perennial weed which reproduces by seed and rhizomes. It produces white to light purple, 5-petaled flowers and green berries that appear wrinkled and yellow when mature.
Quackgrass, Elytrigia repens, is a native perennial which reproduces by seed and rhizome. Seeds are produced in narrow, flat spikes.
Mugwort, Artemisia vulgaris, or wild chrysanthemum is an introduced perennial weed which reproduces by seed (although rarely in northern climes) and by rhizomes. Greenish-yellow flowers are produced in leafy panicles.
Canada thistle, Cirsium arvense, or creeping thistle is an introduced perennial reproducing by seed and creeping roots. It produces heads of rose-purple or white disk florets.
Hedge bindweed, Calystegia sepium, is a native perennial reproducing by seed and creeping roots. It produces white or pinkish funnel shaped flowers on long, axillary stalks.
Japanese knotweed, Polygonum cuspidatum, is an introduced perennial reproducing by seed but more vigorously through an extensive rhizomatous system. Leaves redden as they mature and flowers are greenish-white panicle clusters. While there are many products and methods for treatment and removal of this invasive, noxious weed often an integrated plan is the most effective.
Poison ivy, Toxicodendron radicans, is a native perennial reproducing by seeds and creeping roots. It can be found in clumps on the ground, as a trailing vine or creeping up tree trunks. Leaves are alternate, shiny and randomly toothed, some young ones have a reddish hue. There is still time to treat poison ivy in September but it will senesce soon nonetheless.
The summer of 2014 has been an interesting weed season, while some of the usual suspects were an overwhelming issue others never really put up a fight. Of course, issues are site and condition dependent. Now is a good time to review your treatment program with your arborist, discuss ongoing issues and goals for the future. Next season can be entirely different than this one, but chances are if you get a jump on it early and use the correct products and methods the results should be satisfactory.
