June 1, 2013

1 - If you are going to use a weed control product, it is important to use the right one and to use it properly.

Yard and Garden June 1, 2013


I planted a lawn last year and it is doing great, but this year there are weeds coming up. Is the grass is too young to use a weed and feed product on it.


Herbicide product labels should identify what kind of grass it can be used on (warm season or cool season grass). Be sure the right product is chosen for your lawn. Then be sure it is labeled to control the specific weeds that are growing. If there are trees and shrubs in, or near, the lawn area a broad-leaf herbicide in the weed and feed product can harm the trees and shrubs. Your local NMSU County Extension Service agent can help you identify the grass type and the species of weeds present.

Since you planted the grass last year, I suspect the grass is old enough to use the weed and feed product, but without seeing it or the product label, I cannot be totally sure. If the grass has grown enough that you can mow it, and has begun forming "tillers" (branching at the base), it can probably tolerate the herbicide product. Your County agent can help you read the label, noting the active herbicide ingredients, and advise you whether or not it is safe for your type of lawn. You should also look for information regarding how long to wait after planting the grass before using the product.

Is a combined weed and feed needed? Gardeners can often keep weeds under control in the lawn by watering and fertilizing to strengthen the grass and mowing to keep the weeds (especially annual weeds) from maturing. This will allow the grass to overwhelm the weeds.

Separate fertilizer and weed management products sometimes make sense, especially when nearby trees and shrubs are at risk. The herbicide can be carefully applied to just the weeds and thereby minimize the effect on trees and shrubs. When a weed control product is used, the lawn should be well watered before applying the herbicide. The product should be applied while the grass is still somewhat wet (unless the label says otherwise). Then the lawn should not be watered for several days to allow the chemical to be absorbed into the weeds and to decompose in the environment so it will not be washed into the tree and shrub root zone with a following irrigation.

Some gardeners have decided to abandon lawns because of these considerations regarding weed management. However, even in landscapes without lawns weeds can be a problem. The considerations mentioned above - type of herbicide and proper application remain important.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.


For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook page.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!