Weed and feed is a combination product pairing lawn fertilizer with an herbicide for turf management. The “feed” component supplies essential nutrients, primarily nitrogen, to promote healthy grass growth, while the “weed” component contains chemicals designed to control unwanted plants. Precise timing is important, especially in Kansas, because the effectiveness of the fertilizer and herbicide depends on the biological activity of the grass and weeds. Applying the product at the wrong time can waste the material, fail to control weeds, or even damage the turf by stressing the lawn when it is not actively growing. The proper window for application must align with specific biological events, such as when weed seeds are germinating or when grass roots are actively taking up nutrients.
Understanding Kansas Grass Types and Climate
Kansas is located in the “transition zone,” supporting both cool-season and warm-season turfgrasses. Cool-season grasses, such as tall fescue and Kentucky bluegrass, are dominant in the eastern and northern parts of the state, actively growing during the cooler temperatures of spring and fall. These grasses tend to struggle and may go dormant during the intense heat of a Kansas summer.
Warm-season grasses, including Bermuda grass and Zoysia grass, are more common in the southern and western regions, thriving in temperatures between 80 and 95 degrees Fahrenheit. These grasses remain dormant throughout the winter and only begin active growth when soil temperatures consistently warm up in late spring. Since active growth timing differs significantly, weed and feed application must be tailored to the specific grass species on your lawn.
Spring Application Timing
Spring application focuses primarily on pre-emergent control, targeting the germination of crabgrass. This treatment must be applied before the crabgrass seeds sprout, which is directly linked to soil temperature, not air temperature. The window for a successful pre-emergent application opens when the soil temperature at a two-inch depth consistently reaches 50 to 55 degrees Fahrenheit for several consecutive days.
In Kansas, this thermal requirement typically translates to a calendar window between late March and mid-May, with Eastern Kansas often warming up earlier than the western and northern parts. Applying the pre-emergent too early risks the product degrading or washing away before the weed seeds are ready to germinate, rendering the treatment ineffective. Applying it too late means the crabgrass has already begun to sprout, and a pre-emergent product will not control it.
For cool-season lawns like fescue, the spring application also includes a modest amount of fertilizer to help them green up without encouraging excessive growth that can lead to disease in the summer heat. Warm-season grasses should not receive a spring weed and feed until they have fully emerged from dormancy and have been mowed a couple of times. Applying fertilizer too early to Zoysia or Bermuda grass will only encourage the growth of cool-season weeds, which are their main competition during that time.
Fall Application Timing
Fall application is crucial for lawns in Kansas, especially for cool-season varieties. This window typically runs from September through early November, and its focus shifts from pre-emergent control to post-emergent broadleaf weed eradication and root fortification. Weeds like dandelions, clover, and henbit are actively preparing for winter during this time and are moving nutrients down to their root systems for storage.
Applying a broadleaf herbicide in the fall is highly effective because the weed will pull the chemical down into the roots along with the stored nutrients, resulting in a more complete kill. This strategy prevents the weeds from overwintering and significantly reduces the population that will emerge the following spring. The fertilizer component of the fall treatment, often called a “winterizer,” is formulated to promote deep root growth and increase the grass’s carbohydrate reserves.
This late-season feeding strengthens the root system, helping the grass recover from summer stress and improving its cold hardiness before winter dormancy sets in. A strong fall feeding leads to a denser, healthier lawn that is better equipped to withstand the cold and green up vigorously the next spring. For cool-season grasses, September is considered the most important time for nitrogen application to achieve maximum benefit.
Environmental Conditions for Successful Application
Beyond seasonal timing, immediate environmental conditions affect the product’s success. Most granular weed and feed products require the weed foliage to be damp so the herbicide granules can stick to the leaves for absorption. Applying to a dry lawn will reduce the herbicide’s effectiveness.
Avoid application when the wind speed is high, as the granules can drift onto garden beds or sensitive ornamental plants, causing unintended damage. Temperature extremes must also be considered; applying weed and feed when the air temperature exceeds 85 degrees Fahrenheit can stress the lawn and lead to “burning” or chemical injury, especially on cool-season grasses.
After application, check the product label, but generally, avoid watering or rainfall for 24 to 48 hours to give the herbicide time to be absorbed by the weeds. The exception is a pre-emergent product, which usually requires a light watering soon after application to activate the chemical barrier in the soil.