By Toni Stephan
Oregon State University Extension Service
Weeds are popping up in my lawn. What do I do?
Q: How do I control the dandelions in my lawn?
A: Years ago, lawns used to be a mix of many different types of plants, so we didn’t worry about weeds in the lawn. These days, homeowners prefer their lawns to be one type of plant, grass, which creates a consistent look and feel. So how can you maintain that desired weed-free lawn?
The first step is creating and maintaining a healthy and vigorous turf grass. Healthy lawns out-compete weeds by shading the soil and reducing germination of the weed seeds.
You can create a strong, vigorous lawn through proper care. This care includes mowing at the correct height, watering to a depth of 4 to 6 inches at correct intervals, thatching and aerating, reducing activities that create compaction, proper fertilization and adequate amounts of sunlight.
Another cultural step you can take is to make sure weeds in other parts of the yard are controlled. Don’t let weeds in your lawn or landscape go to seed or you will fight them later on; you may have heard the saying “one year of weed seeds, seven years of weeding.” In a healthy lawn, if a few weeds do spring up it’s easy to remove them by hand methods.
If you have too many weeds to remove them by hand, then you may need to use herbicides. Herbicides are products that can help you control weeds, but without improving the health and vigor of your lawn, you will be fighting a continuous battle.
There are two primary types of weeds that can invade a lawn. One is the broadleaf type such as dandelion or clover. The other is grassy weeds, that will be addressed another time.
Broadleaf weeds are commonly controlled after they come up (postemergence). A selective herbicide containing the ingredients 2,4-D, MCPA/MCPP or Dicamba will kill some broadleaf weeds without damaging your lawn. Products that combine more than one of these ingredients will kill a wider variety of lawn weeds. They can be found easily at local merchants in Central Oregon.
For really tough broadleaf weeds like clover, black medic and chickweed, combinations of the above with additional ingredients such as dichloroprop, triclopyr or carfentrazone may be necessary. You will find the list of ingredients on the herbicide product label.
The best timing for use of those chemicals is in the spring when weeds are small and weather is cool and/or in the fall. Those herbicides are systemic, so they are moved to all parts of the plant. It may be a week or more before you start to see any effects. Fall applications are especially good for controlling perennial, broadleaf weeds as the herbicide is taken to the root and kills it. This leads to a much cleaner, less weedy lawn the next spring.
In addition to using herbicides, it’s also important to incorporate hand pulling of really tough weeds. Using the same chemicals time after time can create resistant weeds. As new weeds come up during the season, hand remove them too or spot spray. This integrated approach will pay off in the long run.
It is important to know that some of the broadleaf herbicides move through the soil and can be picked up by roots of plants that encroach under the lawn. Therefore, it is imperative that you read the entire label of any product you think about using before you buy the product. You don’t want to buy something that will create negative consequences.
Those products also have temperature use limits. You need to know what those are and for how long temperatures need to be maintained for proper use. Herbicides work best on actively growing weeds. Using the suggested amount of chemical is also important as too little may not be effective and too much may create unintended damage to the lawn. The label has this information, plus much more, so be sure to read it.
By the way, the label is the law when it comes to pesticide use!
A couple of years of integrated weed management paired with maintaining a healthy lawn should enable a person to minimize the number of weeds in her or his lawn and significantly reduce the use of herbicides.
— Toni Stephan is a horticulture and small farms instructor at Oregon State University Extension Service in Bend.