Herbicides can target weeds before they germinate from seed – pre-emergent – or as developed plants – post-emergent. Before you seed, you can use a non-selective, post-emergent herbicide to control any weeds in the area to be seeded. Most of these can be applied up to two weeks before seeding to control any existing weeds. Herbicides should not be used after seeding until the new seedlings are established. Mowing and spot treatments can be used to control weeds until the seeded area is actively growing and requires only maintenance watering. Establishment times vary depending on the type of seed you use and your weather conditions.
It is important to know what kind of grass you have growing or want to have growing. Certain chemicals act differently on different species of grass and weeds. For example, the common herbicide 2,4-D is toxic to some cultivars of St. Augustine grass (Stenotaphrum secundatum), which grows in the area roughly covered by U.S. Department of Agriculture plant hardiness zones 8 through 10. Another common herbicide, atrazine, is potentially lethal to grass when applied in temperatures above 85 degrees Fahrenheit. Use the instructions on the bag of each weed and feed product to determine how it will affect seeding.
It’s important to know a little about herbicides so you can make the best choice for when to apply seed in an area that has been treated for weeds. The most common types of herbicide in weed and feed products are selective and systemic. Selective herbicides target a species of plant to kill while systemic herbicides work by being absorbed though the roots and then transported throughout the plant, killing it from within. Read the bag label to see what kind of herbicide is used in the weed and feed you are considering using or have used. The bag label will tell you how many days you must wait before applying seed to a lawn that has been treated with that product.
Weed and feed fertilizers are often used in combination with seeding. Weed and feed formulations consist of two components: a herbicide to kill weeds and a fertilizer to strengthen the turf. The herbicide will weaken the grass as well as the weeds and the fertilizer will strengthen the weeds as well as the grass. When applying seed over a weed and feed application, remember that some weed and feeds can prevent grass seeds from growing.
Only use a weed and feed if the weed infestation is completely uniform over the entire lawn and all species of weeds targeted will be affected by the herbicide in the weed and feed. This scenario doesn’t occur often, so it is more likely the use of an herbicide and a fertilizer separately will be needed. If the weeds are uniformly spread over the area to be treated, match the appropriate weed and feed product to your grass, the seed you have recently applied or want to apply, and the time of year.
Sara DeBerry is a graduate of the University of Florida holding a masters degree in environmental horticulture and a minor in entomology and nematology. DeBerry has been writing for government agencies since 2004 and has published peer reviewed scientific articles during her studies at UF.
Before applying any fertilizer or herbicide product, put on a mask, safety goggles, gloves, long sleeves, long pants and closed toe shoes. After applying the weed and feed and cleaning the spreader, wash your clothing in hot water and detergent to remove any dust or residue.
The Scotts website question-and-answer section states that grass seeds should be allowed to germinate and grow tall and strong enough to be mowed four times before you apply weed and feed. No entirely specific time period is provided, because different grass species grow at different rates, and growth is affected by many variables, including soil quality, temperature and rainfall or manual irrigation.
If you have a very small lawn, an alternative to the granular Scotts weed and feed products is the Scotts Liquid Turf Builder with Plus 2 Weed Control. This liquid fertilizer provides a quick boost of nitrogen as well as killing clover, dandelions and other weeds. Simply attach the garden hose and spray the lawn when the weeds are actively growing.
The Nitty Gritty
Scotts Super Turf Builder with Plus 2 Weed Control, now called simply Super Turf Builder with Weed and Feed, contains more nitrogen and phosphorus than plain Turf Builder Weed and Feed, to provide faster green-up. Super Turf Builder contains 29 percent nitrogen, 2 percent phosphorus and 3 percent potassium, while plain Turf Builder contains 28 percent nitrogen, no phosphorus and 3 percent potassium. The active weed-killing ingredients are 2,4-D and mecoprop. Environmental health agencies in some areas list 2,4-D as a chemical known to cause cancer or birth defects, so use with caution.
If you are unable to find Super Turf Builder Weed and Feed, Scotts Turf Builder Triple Action provides similar results. It kills weeds, prevents the new weeds from sprouting and feeds the grass.
A well-kept, healthy lawn should be plush, free of weeds and diseases, and as green as the neighbors’ envious hearts. Weed and feed products are designed to provide needed nutrients to the grass while poisoning weeds that want to steal the lawn’s food. Scotts Super Turf Builder with Plus 2 Weed Control works on several species of lawn grasses. While the company’s website recommends waiting four weeks to put down grass seed after applying the weed and feed, seeding first means waiting a different length of time before you use the product.
Wait for a calm day when temperatures are not expected to rise above 90 degrees Fahrenheit and no rainfall is expected for at least 24 hours. Water the lawn first to moisten the grass, or start the application when the grass is moist from dew. The product should be applied while weeds are actively growing in the lawn. A second application may be made, but wait at least 30 days — and do not use the product more than twice each year.
Scotts Turf Builder Weed and Feed 3 is a fertilizer and post-emergent herbicide, so it is designed to be used in late Spring when target weeds are young and actively growing. You can reapply after at least 30 days as long as your turf is listed as safe. Do not make more than 2 applications per year. In the fall, do not treat centipede after the first of October and do not treat bahia after the first of November. Wait at least one month after using this product to seed, sod, or plant grass sprigs. Please refer to the product label for complete instructions.
According to the product label, you do not want to water the lawn within 24 hours after application of Scotts Turf Builder Weed and Feed 3.
You want to wait at least 2 days before mowing after applying Scotts Turf Builder Weed and Feed 3
It is recommended not to mow within 2 days before or after application of Scotts Turf Builder Weed and Feed 3.
It is recommended that you wait at least one month after an application of Scotts Turf Builder Weed and Feed 3 to reseed.
Scotts Turf Builder Weed and Feed 3 is safe for pets when it is used according to the product label. You want to make sure pets are not in the area while applying the product. Once the treated areas dry completely, chewing or eating grass will not be harmful and your pet can resume normal activity within the area.
According to the product label, you do not want to water the lawn within 24 hours after application of Scotts Turf Builder Weed and Feed 3. It does not require watering in after application.