Ask any gardener, and it’s likely you’ll hear that the single most common mid summer garden challenge is the management of weeds. A weed is generally considered to be a plant that grows aggressively and reproduces quickly where it is not wanted. In fact, many plants considered weeds in some regions are valued as desirable food, wildflower or ornamental plants in other areas. Dandelion, teasel, purslane, goldenrod, Euonymus, sweet-fern and sumac are several examples.

Gardeners are intent upon eliminating weeds, and rightfully so: weeds crowd-out desirable plants, hoard moisture, nutrients and sunlight needed by garden plants, host pests and diseases and look unsightly.

Weeds can be categorized as annuals, biennials or perennials (see Chart below).  All weeds germinate from seed when conditions are right and grow quickly, potentially dominating a previously pristine patch of ground. The best weed control is to eliminate them at first appearance (pull them out while they are small!), or better, to prevent germination by mulching or applying pre-emergent weed control. Particularly with perennial types, once weeds become established in the ground, management becomes more difficult. The fundamental principle is to control weeds before they begin producing seed.

Perennial weeds re-grow from their roots and underground stems. Herbaceous perennials die back to the ground in winter, making them difficult to spot until their new growth appears, while the stems of the woody types are visible year round.

Some perennial weeds have stoloniferous roots that run in the ground and tend to break off when pulled, each root piece potentially growing into a new plant. Perennial vines attach themselves to desirable plants, often winding and climbing in ways that make their removal very challenging. Some established perennial weeds require chemical herbicides to eliminate them completely. Many of these are now classified as “invasive” which designates them as a serious threat to native plants in natural areas.

Mulching with 1 to 2 inches of loose organic matter like bark mulch, ground-up leaves or wood chips helps discourage weed germination. Some gardeners use plastic or fabric mulches and chemical herbicides to prevent germination. Weed management choices depend upon a variety of style and plant-type considerations, and many people prefer to limit chemical techniques.

Effective weed management requires planning, persistence, monitoring, and often a good measure of sweat in the summer. But the reward of an attractive, well-managed garden is worth the effort.

CHART

Types of Weeds*

Annual Weeds germinate, flower, produce seed and die in one year. Common examples in this part of New England are crabgrass, purslane, lambsquarters and ragweed.

Biennial Weeds germinate and grow their foliage the first year, only flowering and producing their seed after going through winter. Some typical examples in this region are garlic mustard, burdock, brome grass, evening primrose and Queen-Anne’s lace.

Perennial Weeds have long-lived root systems that persist year after year.

• Simple root systems that are relatively easy to remove intact
  • Herbaceous (tops die to the ground in winter). Examples are dandelion, pokeweed and bull thistle.
  • Woody plants whose above ground parts are visible all year
    • Trees and shrubs: autumn olive (Eleagnus), buckthorn (Rhamnus), barberry (Berberis), wild rose and burning-bush (Euonymus alatus)
    • Vines: poison ivy, nightshade.
• Stoloniferous or persistent roots from which new plants re-grow when roots are broken off or left in the ground
  • Herbaceous: Examples are bindweed, witchgrass (evergreen), Canada thistle, hairy vetch, clover (evergreen), groundnut (Apios) and kudzu.
  • Woody & Semi-woody plants:
    • Trees and shrubs: Japanese knotweed, sumac, sweet fern, brambles.
    • Vines: Bittersweet (Celastrus), Virginia creeper, bull briar.

*Categories and list compiled by Hort-Sense, 2008