Weed and Feed is a popular lawn care product that combines granular fertilizer with a broadleaf herbicide, creating a dual-action treatment for turf. This single application is designed to simultaneously nourish the grass and eliminate unwanted plants. However, because this product contains two distinct chemical compounds with different requirements, timing the application correctly is the single most important factor for maximizing effectiveness. Applying the product at the wrong time can significantly reduce its benefits, potentially harming the grass or failing to control weeds.
Understanding the Dual Action of Weed and Feed
The product’s efficacy relies on two components working at different stages of plant development. The fertilizer portion, typically rich in nitrogen, phosphorus, and potassium, is meant to be absorbed by the grass roots to encourage dense, healthy growth. This nutrient delivery is most effective when the turf is actively growing.
The herbicide component can be either a pre-emergent or a post-emergent formula, and sometimes both. Pre-emergent herbicides function by creating a chemical barrier in the soil that prevents weed seeds from successfully germinating. Post-emergent herbicides are designed to kill weeds that have already sprouted and are actively visible above the soil line.
The timing challenge arises because these two actions have different requirements. Post-emergent herbicides often need to stick to the moist foliage of existing weeds to be absorbed into the plant’s system. Conversely, the fertilizer needs to reach the soil for root absorption, usually requiring watering to break down the granules. Therefore, post-emergent application must be delayed until weeds are visible and the grass is damp, while a pre-emergent must be applied before germination occurs.
Critical Timing for Spring Application
The first application of the year is generally the most important, and it is entirely governed by soil temperature, not the calendar date. For pre-emergent effectiveness against common annual weeds like crabgrass, the product must be applied before the soil temperature consistently reaches 55 degrees Fahrenheit. Crabgrass seeds begin to germinate when the soil temperature maintains this 55-degree threshold for several consecutive days.
Applying the pre-emergent component too early risks the chemical barrier breaking down before the weed seeds begin to sprout. Applying it too late means the crabgrass has already germinated, rendering the pre-emergent useless. Homeowners can monitor local soil temperature online through agricultural extension websites or use a simple soil thermometer to ensure they hit the narrow window when the soil is hovering around 50 to 52 degrees Fahrenheit.
Timing is slightly different depending on the type of turfgrass. Cool-season grasses, such as fescue and bluegrass, begin their most vigorous growth period in early spring and benefit from the initial fertilizer boost. Warm-season grasses, like Bermuda or Zoysia, do not begin active growth until soil temperatures are consistently warmer, often closer to 65 or 70 degrees Fahrenheit. For warm-season lawns, it is often better to apply a weed-only control product first, then follow up with fertilizer once the grass is fully out of dormancy.
Adjusting Application for Summer and Fall
Mid-season applications of Weed and Feed should be approached with caution, especially during the summer months. Most turfgrass, particularly cool-season varieties, become stressed and enter semi-dormancy when air temperatures consistently exceed 85 to 90 degrees Fahrenheit. The high nitrogen content in many fertilizers can cause a chemical burn on heat-stressed grass blades, damaging the lawn more than helping it.
If weeds persist throughout the summer, it is often safer to spot-treat them with a liquid post-emergent herbicide rather than blanket the entire yard with a combined product. The subsequent application of Weed and Feed is best reserved for the fall season, which is a significant period for turf health. Fall application should occur approximately six to eight weeks before the first hard frost is expected in the region.
This autumn application, sometimes referred to as a winterizer, is primarily a nutritional feed focused on root development and energy storage. For cool-season grasses, this late-season feeding is considered the most beneficial application of the entire year, as the grass uses the nutrients to strengthen its root system. Warm-season grasses should receive their final feeding six weeks before dormancy sets in, but caution is warranted to avoid stimulating new growth that could be damaged by an early frost.
Essential Steps Before and After Application
It is recommended to mow the lawn two to four days before application to ensure the granular herbicide can make good contact with the broadleaf weeds. The weeds should ideally be slightly damp from dew or a light sprinkling, as the granules need to stick to the foliage for the chemical to be absorbed effectively.
After the granules are spread uniformly across the lawn, the critical follow-up step is to delay watering or rain. The post-emergent herbicide requires a contact period of 24 to 48 hours to be fully transferred from the granule to the weed tissue. Washing the product off too soon will reduce the weed-killing power and waste the application effort.
After the required waiting period, a thorough watering is necessary to dissolve the granules and carry the fertilizer down to the root zone. This watering also washes any herbicide residue off the grass blades, preventing potential foliar burn. For safety, keep children and pets off the treated area until the product has been watered into the soil and the grass has completely dried.