Recognizing Weeds

By definition, a weed is any plant that is growing where you do not want it to grow. Flowers growing in the lawn or grass growing in the flower bed would be considered weeds. Botanically, there are three types of weeds: broadleaf (ex. dandelion), grassy (ex. crabgrass) and grass-like (ex. wild onion).

Weed seeds exist in almost all lawns and gardens, and can be spread in a number of ways. They can be dispersed by wind, water, animals, soil amendments, poor quality grass seed and lawn and garden equipment. Many weed seeds remain dormant for years before they begin to grow since they must reach the soil's surface and receive the proper amount of sunlight and moisture before they germinate.

There are three main classifications of weeds—annuals, biennials and perennials.

Annuals normally grow, produce seeds and then die within a single year. In warmer climates, some annuals may survive a second year. In general, annual weeds are the easiest to kill.

Biennials live for two years. The first year is devoted to vegetative development, the second year to flowering and seed development.

Perennials live from season to season and produce seeds each year.

In the fight against weeds, the most important element is to promote the best environment possible for the growth of desirable plants. Improper watering or fertilization, soil compaction, insect damage, disease, poor drainage, improper sunlight and too much wear on lawns are all conditions which increase the potential for weed development. To reduce lawn weed problems, it is also important to mow the grass at the proper height. Mowing the lawn too short decreases the grass's ability to shade the soil from sunlight, thereby increasing the potential for weed germination.

The best time to attack all weeds is when they are young, tender and actively growing. Manually removing weeds, either by hand or with a weeding hoe, is the safest and most selective method available. This may not be practical, however, for large lawns or gardens—or areas overgrown with many weeds. In this case, you may choose to use herbicides.

Using Herbicides to Eliminate Weeds

Herbicides are divided into two main categories: systemic and contact.

• Systemic herbicides enter the plant through the roots and leaves and move throughout the inside of the plant.
  
  
• Contact herbicides kill from the outside in. They attack the exposed parts of the plant, killing the weed by reducing its ability to feed itself through photosynthesis.
  

Within these two categories, herbicides may also be divided into selective and nonselective varieties.

• Selective herbicides, when applied as directed by the manufacturer, kill only certain plants. A good example of a selective herbicide is a lawn weed killer designed specifically for the removal of broadleaf plants. These products will remove the weeds without killing the established lawn in which the weeds grow. Young, freshly sewn grass would still be susceptible to the herbicide, however, since it would not have had an opportunity to fully establish itself.
  
  
• Nonselective herbicides kill plants without discretion. They will kill all plants they come into contact with. These products can be used, for example, when preparing an area for planting or when attempting to reestablish a new lawn. Through their use, all traces of vegetation—including problem plants—can be removed from an area, thereby giving the gardener a clean slate with which to work.
  

Herbicides are also categorized as pre- or post- emergent.

• Pre-emergent herbicides are applied before the targeted weed germinates, and are an effective preventative method for controlling weeds. Crabgrass preventer is a good example. Pre-emergents establish a chemical barrier that will not kill established plants, but will prevent weeds from successfully growing. The protective barrier breaks down in six to eight weeks. Use of a pre-emergent, therefore, requires proper timing to be effective. Be aware that pre-emergents can harm some desirable ornamental plants and turf grasses. As always, read and follow the manufacturer's instructions.
  
  
• Post-emergents are designed to attack weeds that are already established and growing. All of the contact weed killers are post-emergents.

Preventing and Controlling Weeds

Remember a few key things about weed control:

• Do not mow or prune before product application. The more leaf surface, the better.
  
  
• Do not mow or prune for several days after application. This will give the chemical time to be absorbed.
  
  
• Herbicides are most effective on young, actively growing plants.
  
  
• Young plants may not be mature enough to fight off the effects of most herbicides. Make sure the plants you want to keep are mature enough to withstand the effects of the chemical.
  
  
• After plants have germinated, spot treatment is the best choice to avoid chemical damage to desirable plants.
  
  
• Discard contaminated pruning materials and clippings to prevent the spread of weeds to other planting areas.
  
  
• Avoid spraying chemicals on windy days.
  

 

Weeding large areas

• Large areas can be treated with a hose-end attachment that mixes herbicide with water from a garden hose to apply to the lawn.
  
  
• Granular herbicides can also be applied with a broadcast or drop spreader.
  
  
• Whichever method you choose, read the product instructions carefully and wear the recommended safety equipment.
  

 

One weed at a time

• Use a weedkiller spray for spot weeding. Do not spray on a windy day or it will drift and kill patches of lawn.
  
  
• Apply liquid weedkillers directly onto the weed to kill the entire plant. Repeat as necessary and do not apply to the lawn.
  
  
• For the natural gardener, weeding by hand is an alternative. Using a garden fork, dig underneath the weed. Keep the hole as small as possible. Grab the weed under its crown and pull out the entire root. Follow an Integrated Pest Management schedule for best results.
  

Weeding Schedule

Early Spring - Inspect your lawn as spring approaches, then decide on the treatment. Apply a pre-emergent shortly before annual weeds, such as crabgrass, begin to grow in the spring. A good rule is to apply the pre-emergent before the dogwoods begin to bloom. You may decide to use a pre-emergent combined with fertilizer as an early lawn treatment.

Late Spring - In the middle of the growing season, determine which weeds have come back and repeat weed killer application or remove weeds selectively with herbicide or by hand.

Fall - Treat your lawn one last time with a general weed killer after the final mowing. Remove large weeds by hand to ensure they will not survive over the winter.

Safety Tips for Weed Control

To ensure your personal safety and the maximum benefits of the product:

1. Always follow the manufacturer's directions.
   
2. After application, keep children and pets off a treated lawn for at least 48 hours, or until the lawn is dry.
   
3. Store chemicals in a cool, dry and dark place safely out of children's reach.
   
4. Always wear gloves, long pants, a long-sleeved shirt and rubber boots when applying weedkiller. Wash out all clothing after use.
   
5. Keep separate cans for watering and for chemicals.
   
6. Be sure to use only the recommended amount of weedkiller to prevent buildup in water tables that can harm the environment.
   
7. It is important when using any chemicals to closely follow the manufacturer's instructions. Failure to follow the manufacturer's recommendations can increase the dangers associated with their use, as well as decreasing their effectiveness.

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