Looking at weed control as Spring approaches

In honor of the North American Invasive Species Awareness week we’re going to be taking a closer look at managing weeds.

Weeds do not recognize property boundaries. My weeds are your problem and your weeds are my problem. Every one of us needs to be involved in weed control, because ignoring the weeds will not make them go away.

As the snow recedes, there will be lots of little weeds (annuals and seedlings, biennial rosettes [low mat of leaves waiting to bolt and produce flowers], and early perennials) in position to take advantage of the warming spring weather.

I will present some springtime control options for each of these life-cycle types.

Annuals and seedlings

Mechanical removal: Hoeing, tilling or pulling annuals before they go to seed, and seedlings of biennials and perennials, is the surest way to control weeds in small areas. New seeds may come to the surface.
Flame weeding: Propane torch, hot air, or steam, directed at the base of small plants will kill the stem. No new seeds are brought to the surface. Not as effective on grasses.
Mulch: A three- to six-inch layer of woodchip mulch will help reduce annual and seedling weed pressure. Refresh with another inch every year or two. Large wood chips are better than decorative bark. Weed seedlings that do grow up through the mulch layer are easier to pull.
Herbicide: Herbicides are most effective on small plants. Organic burn-down herbicides such as ammonium nonanoate, pelargonic acid, and horticultural vinegar usually do very well on young plants.

Biennial rosettes

Mechanical removal: Biennials produce significant taproots before winter. Use a shovel to remove three to four inches below the crown before they produce a seed head. Remove and discard any flowers. Compost or till in the vegetative tissues. Monitor and repeat as necessary.
Weed barrier/mulch: A weed barrier under mulch stops biennials from growing up through the mulch layer. Weed barrier materials should be breathable.
Herbicide: Spring herbicide application on biennials should be done before a flower is formed. The response can be quite good on rosettes or early bolt stage. If a flower has formed, remove and discard the flower as it may still produce viable seed while the herbicide does its job.

Simple perennials, like dandelion

Mechanical removal: Removal three to four inches below the crown several times a year.
Weed barrier/mulch: A weed barrier under mulch will stop simple perennials from growing up through the mulch layer. The weed barrier should be breathable.
Herbicide: Usually most effective in the fall, systemic herbicides to kill the root should be applied when there is enough leaf surface to absorb the herbicide.

Creeping/spreading perennials, like quackgrass and bindweed

Mechanical removal: Not effective, chopped up rhizomes and roots may generate many new plants.
Weed barrier/mulch: A weed barrier under mulch will stop most creeping perennials from growing up through the mulch layer. The weed barrier should be breathable.
Herbicide: Usually most effective in the fall, systemic herbicides to kill the root should be applied when there is enough leaf surface to absorb the herbicide.

Combinations of these different control options will give best results.

When using herbicides, always read and follow the label, even if it is listed as an organic product.