Description

• Just like vegetables and ornamental plants, weeds can be annual or perennial, and can emerge at different times of the year. Summer annuals sprout in the spring and can flower through summer and into fall. Crabgrass is one of the most common annual broadleaf weeds. Winter annuals aren't generally as troublesome for gardeners. They include wild mustard and common chickweed. Perennial weeds are perhaps the most difficult to control. Herbicides must be applied over many growing seasons, and tilling may just spread weeds further. Bermudagrass is an example of a stubborn perennial weed.
  
  

Origins

• Broadleaf weeds can enter your garden through a variety of methods. Many seeds exist in the soil naturally and can lie dormant there for as many as 30 years, according to Purdue University extension. Weeds survive because they've adopted good strategies for spreading. Those that spread via seed can produce thousands at a time, and these seeds can be spread for miles by the wind. If you add topsoil to your garden, you may be adding weed seed, too. Many commercially available topsoils can contain weed seed.
  
  

Mulching

• Mulching is perhaps one of the easiest ways to control weeds. By prohibiting light from getting through to weed seed, mulch prohibits germination. Mulch can also suppress perennials for the same reason. Without sunlight, perennial weeds won't be able to spread. Mulch comes in two categories: organic and inorganic. Organic mulches can be anything from grass clippings or pine bark to straw. Inorganic mulches include black plastic mulch or fabric made of polypropylene or polyester. Black plastic mulch has the disadvantage of prohibiting oxygen and water from reaching the roots of garden plants.
  
  

Cultural Control

• For gardeners uncomfortable using herbicides in vegetable or flower gardens, cultural control is key. Unpleasant as it is, pulling weeds by hand is effective. Even if you don't get the roots when you pull, repeatedly prohibiting the growth of a weed will eventually weaken and kill the root system. And if you use hand-pulling in conjunction with mulch, you may not have many weeds to pull. Planting your vegetables and flowers close together creates what Clemson University Extension calls a "crop canopy." Closely spaced plants will form a shade barrier that makes it difficult for weeds to germinate and thrive.