Using Cultural Practices and Non-Chemical Weed Control in the Landscape and Garden

Spring has arrived in New England and brown slowly turning to green marks the start of another gardening season when gardeners experience renewed enthusiasm for their ornamental landscapes, lawns and vegetable gardens. Whether it is new gardening endeavors or projects from last season that did not work out as favorably as one would have liked, now is the time to look forward to a fresh start.

One of the things gardeners are not looking forward to is another season of battling with the unwanted plants known as weeds. In recent years, an increasing number of gardeners have sought weed control solutions that do not rely on the use of chemical weed control products.

Recently, a variety of non-chemical weed control products have been made available in garden and home centers. Unfortunately, many of these products will not provide the desired level of weed control. The only group of products that may provide some effective weed control are the “contact”, non-selective products which contain the active ingredients acetic acid, clove oil, citric acid, or potassium salts of a fatty acid. Available products that contain these active ingredients, either individually or in combinations, can be used to control young summer and winter annual weeds or seedlings of perennial weeds. “Contact” products only kill or injure the parts of the plant that are sprayed; consequently, they will not control established perennial weeds, which are able to regrow from their roots. Since these non-chemical weed control products are somewhat limited in their performance, other strategies need to be used that might suppress or reduce weeds in landscapes, lawns and gardens. Here our focus shifts to the use of cultural practices. If you wish to control weeds without using chemical weed control products, begin with the cultural practices and/or strategies suggested below.

Ornamental landscape beds
Landscape mulches are the first and best defense against weeds in landscape beds. Compost should not be used as a landscape mulch, since it provides the perfect medium for growing weeds and may contain weed seeds if it was not sufficiently heated during the composting process. Summer and winter annual as well as perennial weed seedlings can be spot sprayed with one of the non-selective, non-chemical, “contact” weed control products mentioned above to kill the upper portion of the seedling. While these products will not kill landscape tree, shrubs or perennials, overspray to plant foliage nearby should be avoided as temporary injury can occur.

The old adage “Weeds are the result of a poor lawn, not the cause of a poor lawn” leads us in the right direction when attempting in reduce weeds. In other words, a neglected lawn came first and the weeds, having less stringent requirements for growth, followed. Lawns that are healthy and dense have an inherent, competitive advantage against weeds. We encourage lawn grasses to be competitive with the use of cultural practices just as we promote human health with a good diet, exercise, and sufficient sleep. Similarly, lawn grass health is promoted by cultural practices such adequate fertility, soil acidity correction, mowing, irrigation and alleviation of soil compaction.

Vegetable gardens
The key component of weed management in vegetable gardens includes light hoeing or cultivation before the weeds appear or when the weeds are very, very small. Large weeds can be hand-pulled. Mulch materials can also have great value. Straw or saltmarsh hay are good choices, since neither are likely to contain weed seeds. Mulch hay, which often contains many seeds of grasses that become weedy in the garden, and landscape mulches, which are slow to break down and so tie up needed nitrogen, are not recommended and should be avoided.

If, after time, you are not achieving sufficient weed control using non-chemical weed control products and the appropriate cultural practices outlined above, the use of chemical weed control products may be another option. As with both chemical and non-chemical weed control products, gardeners need to read, understand and follow the product directions. This is important not only for safety, but also to achieve the best results a product can offer.