Oh – Those Weeds in My Landscape!
R. Wayne Mezitt
Weeds are sometimes defined as “plants whose virtues are yet to be discovered”. In any case they are undesirable or intrusive plants growing where they are not wanted. Out-of-control weeds in your landscape plantings can make your garden look unattractive. But they also can damage landscape plants by blocking sunlight and stealing the moisture and nutrients your desirable plants need to be healthy. Many weeds also harbor pests, or attract insects and diseases that can cause damage in your landscape.
Plants we consider to be weeds in the landscape have either broadleaf-type foliage or grass-like leaves, and they are of two types. Annual weeds (like crabgrass, chickweed and purslane) are the most common in our landscapes and the fastest growing. These are considered annuals because they germinate from seed each year and do not survive over the winter in this region. Perennial weeds, which also may produce seeds, tend to lose their leaves or die-back to the ground in winter. But perennial root systems survive to produce new growth year after year. Good examples of common perennial weeds are quack-grass, bindweed, dandelion and clover.
If you use mulch around your trees and shrubs, maintenance of annual weeds and just-germinated perennial weeds should be simplified. Weed seeds tend to germinate less readily where the soil is shaded, and those that do come up are easier to pull. Maintaining vigorous plantings helps limit the sunlight that reaches the ground. Planting groundcovers like Vinca, ginger or Pachysandra can also help crowd out undesirable weeds. Even in exposed soil areas, weeds are much easier to remove when they are small before their roots become firmly established. In any case, preventing weeds from producing seed will help reduce future weed problems.
Already-established perennial weeds in the landscape are more difficult to manage. Physically pulling out mature perennial weeds rarely controls them because parts of their root systems break off and remain in the soil to continue growing. Excluding light by mulching with fabric or plastic can help suppress perennial weeds. It is also possible to control perennial weeds with repeated physical removal alone. Some perennial weeds require specific conditions and can be controlled by changing those factors. But in many situations homeowners decide to take the most convenient approach and rely upon use of chemicals for managing established perennial (and even annual) weeds.
Before you resort to using chemicals, it is wise to invest time to identify the weeds you are trying to control and learn about their life cycle. Two main types of chemical weed control are commonly available to homeowners. Make sure if you choose to use chemicals that you carefully follow the directions on the label! Try to go ORGANIC if you can.
- Pre-emergent herbicides prevent weed seeds from germinating, and they must be applied before new growth starts to be effective. Most garden centers carry products like Preen that prevent germination of many types of annual and perennial weeds. These chemicals are generally ineffective on weeds already growing in the landscape. Some more organic herbicides may also be available.
- Post-emergent herbicides that are “non-selective” damage or kill all top growth on which they are applied -- including your desirable landscape plants. Formulations like “Roundup” not only destroy top growth but are systemic and carried into the root system of the plant to retard or prevent regrowth. Some post-emergent herbicides are “selective”, meaning they are effective only on certain types of plants. For example, brush- and poison ivy-killers like “2, 4-D” control only broadleaf weeds (which includes any desirable shrubs they touch), but are not harmful to grasses.
For best weed management it is important to identify the type of weeds you have, understand why they are growing there, and explore the best approach to manage them. Your local garden center is probably the best place to learn more about the weeds that concern you and choices to manage them. Experts there can surely identify weeds, advise you directly or suggest resources where you can learn more about your specific needs. A good website for horticultural information, including weeds, is www.umassgreeninfo.org.
Although chemical controls are widely promoted as the preferred route to a beautiful yard, less intrusive methods may work as effectively. With today’s concerns about chemicals and their effect on our health, it’s prudent to know your alternatives, and often you’ll find it’s possible to limit use of herbicides. Even though parts of your garden may look out-of-control with weeds, your challenges will be a lot easier to manage once you know the facts and work out a reasonable weed management plan.
R. Wayne Mezitt is a third-generation nurseryman
and a Massachusetts Certified Horticulturist,
now chairman of Weston Nurseries of Hopkinton, MA.
He has served as president of the Massachusetts
Nursery and Landscape Association, the New England
Nursery Association, and the American Nursery and
Landscape Association, based in Washington, DC.
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