Treat and kill lawn weeds in the fall. One of the best things you can do for your lawn is to treat weeds in the fall. Because Crabgrass sets seed throughout the growing season, it's worth the effort to apply a pre-emergent herbicide to prevent any late season-released seeds from germinating. For perennial weeds, lawn weeds that are common such as Plantain, Dandelion, Knotweed and Clover weeds, apply a post-emergent herbicide in fall to send the killing chemicals directly to roots. This treatment will help reduce the numbers of these weeds in spring. Learn what types of weeds on lawn, what to do for killing weeds in lawn, and how to adjust the treatment for each with the best weed killer for lawn. Feeding your fall lawn provides helpful nutrients to fight weeds and strengthen lawn grasses for the winter ahead. Should I seed my lawn in Spring or Fall? Seeding in Spring or Fall? A common question from homeowners. One common question I am asked every Spring is, “Should I seed my lawn in Spring or
Treat and Kill Lawn Weeds in the Fall
One of the best things you can do for your lawn is to treat weeds in the fall. Whether you’re tending warm- or cool-season turf, tackling weeds as autumn’s cooler days arrive can help you create a lush and lovely lawn. Fall treatments knock out both annual and perennial weeds and can actually be the key to killing established perennial invaders such as dandelion and clover.
Types of Weeds
Winter annuals, a type of annual weed, germinate in late summer to early fall. They grow in fall, through winter warm spells, and into early spring. These weeds set seed in mid- to late spring, just before daytime air temperatures jump. Examples of winter annual weeds include Henbit, Annual Bluegrass, Chickweed, corn Speedwell and Lawn Burrweed (or Spurweed).
When you treat your lawn for weeds in autumn, you’ll target fall-germinating weeds, such as Henbit and Chickweed (annual weeds). Dandelion also germinates in fall, although compared to spring, the number of seeds germinating is generally less.
Fall is also an excellent time to control perennial weeds, because that’s the time of year when plants begin a process of winter food storage, shifting internal foodstuffs from leaves to roots. If you treat perennial weeds with herbicide in fall, the chemical moves from leaves to roots, essentially killing the weed at the root.
Treatment & Timing
If your fall weed treatments are targeting both annual and perennial weeds, you’ll want a weed killer that combines a pre- and post-emergent herbicide. This is because some weeds will already be growing, which the post-emergent herbicide will kill, and weeds that haven’t yet sprouted will be taken out by the pre-emergent herbicide.
Application timing will vary depending on where you live. In more northern locations, treat lawns as early as Labor Day; warmest areas may apply as late as October.
To find the right timing for your region, you can consider air temperature. Herbicides are most effective when air temperature is 50°F and above. But perhaps the best way to assure proper timing is to contact your local extension agent. They’ll know the right timing for your specific location. To learn more about timing herbicide applications, read our article on “Understanding Weed Killers”.
Some of the lawn interlopers worth treating during the cool season of the year include Annual Bluegrass, which tends to be a problem in warm-season lawns. Crabgrass invades both warm- and cool-season turf. Because Crabgrass sets seed throughout the growing season, it’s worth the effort to apply a pre-emergent herbicide to prevent any late season-released seeds from germinating.
The best treatment for Annual Bluegrass and Crabgrass is a Crabgrass preventer, a pre-emergent herbicide that combats grassy weeds and can be applied in spring or fall. Unfortunately, these products aren’t traditionally sold year-round in all regions. If you know you’ll be dealing with these weeds in fall, it’s best to purchase a Crabgrass preventer in spring and store it in a cool, dry place until autumn’s cooler days arrive.
Wild Onion and its relative Wild Garlic can punctuate a dormant warm-season lawn with bright green exclamation points. Eliminate these smelly weeds with post-emergent herbicide. Lawn Burrweed is a winter annual weed that sets spurred seeds in spring, making a lawn a painful venture for people and pets. Control this prickly weed with a fall application of a pre-emergent herbicide.
For perennial weeds such as Plantain, Dandelion, Knotweed and Clover, apply a post-emergent herbicide in fall to send the killing chemicals directly to roots. This treatment will help reduce the numbers of these weeds in spring.
To identify and learn more about weeds mentioned in this article, check out our Guide to Common Lawn Weeds.
Fall Season Fertilizer and Weeding Tips
Fall’s arrival brings changes in day length, temperature and precipitation, along with important changes in your lawn. Some lawn grasses and weeds begin to slow down and prepare for winter dormancy, but others kick into high gear. Feeding your fall lawn provides helpful nutrients to fight weeds and strengthen lawn grasses for the winter ahead. However, what and when to feed and how to manage weeds depends on your climate and the type of grass you grow.
Feeding Cool-Season Lawn Grasses
Cool-season grasses, such as Kentucky bluegrass, perennial ryegrass and fescues, flourish in northern regions with warm summers and cold winters. Cool, moderate, early fall temperatures send these grasses into their most active growth season, which is the ideal time for fertilizing and strengthening.
Start fertilizing cool-season grasses about six weeks before the average first frost in your area. Fresh out of summer dormancy, these grasses benefit from added fall nutrition, which spurs new shoot, stem and root growth, and helps increase their food reserves. 1 September and October are prime cool-season fertilizing times for much of the United States.
A high-nitrogen lawn fertilizer with added potassium, such as Pennington UltraGreen Lawn Fertilizer 30-0-4, stimulates dense, healthy growth and supports winter and summer hardiness. The added boost of natural organisms from Pennington’s Myco Advantage technology increases the surface area of grass roots, improving your lawn’s ability to absorb water and nutrients, and enter winter prepared.
With broadleaf lawn weeds still actively growing in early fall, a weed & feed product such as Pennington UltraGreen Weed & Feed 30-0-4 fertilizes established cool-season lawns and kills a broad spectrum of common weeds through the help of three separate weed fighters. Follow label instructions closely to ensure you don’t exceed annual limits for broadcast applications.
Fertilizing Warm-Season Grasses
Warm-season grasses, such as Bermudagrass, bahiagrass, centipede grass and zoysia grass, thrive in southern regions and peak in growth during warm summer months. As fall approaches, their growth slows and dormancy sets in with the season’s first killing frost.
Feed warm-season grasses their last feeding of the season six to eight weeks before the average fall frost date in your region. They’re still actively growing, but they’ll soon need to harden off and prepare for winter. Bermuda grass has higher nitrogen needs than some other warm-season grasses, so it can be fertilized up to four to five weeks before frost. 1 But don’t feed warm-season lawns any later. Fertilizing too late in the growing cycle can stimulate late-season growth that delays dormancy and makes lawns more susceptible to winter injury.
Warm-season grasses often go dormant and turn brown during winter, leading many southern lawn owners to overseed lawns with a cool-season grass that provides temporary green color through the winter months. Overseeding should take place at least 45 days before your average first fall frost, so new seeds can establish before winter. 2 Fertilize newly overseeded fall lawns with a starter fertilizer such as Pennington UltraGreen Starter Fertilizer 22-23-4, which supports robust root growth and greening of the cool-season grass. Avoid using weed & feed products on newly overseeded lawns, as they may prevent germination of the new grass seed. Consult your local Cooperative Extension Service for current information on limits for lawn fertilizers in your region.
Managing Fall Lawn Weeds
Like lawn grasses, common lawn weeds are either warm- or cool-season plants that follow the same seasonal growth peaks that lawn grasses do. Annual weeds, such as warm-season crabgrass, complete their life cycle in one year – but leave plenty of seeds behind for years to come. Perennial weeds, including cool-season plantains, live many years. Untreated, they come back from the roots year after year and spread extra seed, too.
Early fall is a perfect time to tackle tough turf weeds. Existing perennial weeds are still active and hard at work storing up food reserves, which leaves them very vulnerable to treatment. Weed killers get swept through the plant along with carbohydrates meant for energy stores in stems and roots, and few parts of the plant escape. 3 As warm-season weeds go dormant, movement through weeds slows or stops and resilience increases, making treatment more difficult.
In established fall lawns, weed & feed products help prevent cool-season weed seeds from germinating and emerging. In dormant southern lawns, emerged cool-season weeds stand out bright green against brown lawn grasses, which makes spot treatment easy. Effective post-emergent weed treatments, such as IMAGE All-in-One Killer, offers broad-spectrum fall control for difficult sedges, crabgrass and broadleaf weeds. IMAGE Kills Nutsedge, available in concentrate and ready-to-spray formulas, controls winter weeds in warm-season lawns, including Poa annua, also known as annual bluegrass, a troublesome annual weed common in Bermudagrass lawns.
Feeding your fall lawn and controlling its weeds helps leave grasses strong and healthy. With the help of the Pennington UltraGreen line of lawn fertilizers and IMAGE weed treatments, your lawn will be ready for the months ahead.
Never use any weed product on a lawn grass unless the grass is noted on the product’s label.
Pennington and Myco Advantage are registered trademarks of Pennington Seed, Inc. Amdro and UltraGreen are registered trademarks of Central Garden & Pet Company.
1. Michael Goatley Jr., Shawn Askew and David McCall, “Fall Lawn Care,” Virginia Cooperative Extension.
2. Turfgrass Water Conservation Alliance; “Simple Tips,” October 2014.
3. Zac Reicher, Cale Bigelow, Aaron Patton and Tom Voigt, “Control of Broadleaf Weeds in Home Lawns,”Turfgrass Science, September 2006.
Should I seed my lawn in Spring or Fall?
Seeding in Spring or Fall? A common question from homeowners.
One common question I am asked every Spring is, “Should I seed my lawn in Spring or Fall?” Many homeowners are eager to start thickening up their lawn as soon as they get a glimpse of good weather in early Spring. We sometimes still have a late March snow on the ground when the calls start coming in. My answer to their question is the ever-popular “It depends.” After explaining the pros and cons to many homeowners over the years, I’ve put my recommendation in writing on this page.
When is the best time to seed my Northern Illinois lawn?
Per the Illinois Department of Agriculture resources and many other university studies, the best time to seed in Northern Illinois is either Spring (the month of April), or early Fall (late August through the 2nd week of September). I am going to make it easier for you and recommend that you stick with early fall. Keep reading to find out why…
Seeding your lawn in Spring
Spring is a great time to seed your lawn, but there are more cons than pros when it comes to seeding this time of year. There are 2 main reasons why you should not seed your lawn in Spring: pre-emergent and summer.
As part of a normal lawn care program, pre-emergent is usually applied in the Spring to help prevent crabgrass and many other types of weeds. That is the good part about pre-emergent. The bad part about pre-emergent is, it also prevents good grass seed from germinating. If you put seed down all over your yard and then a pre-emergent is applied over the top of it, chances are, the seed will not germinate, or will experience a very low germination rate.
Grass plants depend on deep, healthy roots, and a tall, thick stand of grass blades to help it survive the stresses of Summer. Deep roots allow the grass to reach moisture that lies beyond the dried out top layer of soil. A tall and thick stand of grass blades help to shade the soil and prevent weeds from competing with the lawn. When you seed in the Spring, the new grass plants may come up very nicely after a few weeks, but under the soil, the roots will not yet be deep enough to survive Summer without a significant amount of irrigation from a sprinkler system. Unless you keep the seedlings watered all summer long and into early Fall, the chances of their survival is slim to none.
Seeding your lawn in Early Fall
If you seed your lawn in early Fall, the seedlings will have 9 to 10 months to develop deeper root systems before they have to experience their first Summer of hot and dry weather. Compare this to 1 or 2 months for a Spring seeding, and the chances of an early Fall seeding surviving to maturity are significantly greater. On top of that, you can still apply your pre-emergent in Spring and keep out the crabgrass and other weeds throughout the season.
Exceptions to my seeding recommendation
As with any rule or recommendation, there are always exceptions. For example, you may want to seed in the Spring if you had extensive drought or grub damage during the previous summer or fall. Pre-emergent works best on a thick stand of turf, but it does not work well in areas where there is exposed soil and not much grass. In cases like this, you have to compare the pros and cons. If you have a lot of bare spots, and you wait until Fall to seed, you may end up with a lot more weeds in those bare spots throughout the season. If you skip the pre-emergent and seed the bare areas in the Spring, you will prevent a lot of weeds in those bare areas, but you might experience some crabgrass or other weeds throughout the lawn.
Lawn seeding recommendation summary
To summarize, follow these recommendations when seeding your lawn in Northern Illinois:
Repair prior year damage or bare spots in Spring (month of April)
- Apply pre-emergent for crabgrass and other weeds as part of your regular lawn care program.
- Fix bare spots by roughing them up with a garden rake and adding fresh top soil and seed.
- Keep the seeded areas and new seedlings watered throughout the Summer.
Over-seed the entire lawn in Early Fall (late August through early September)
the entire lawn.
- Over-seed the entire lawn.
- You can also repair summer damage this time of year.
If you need any assistance with lawn care, core aeration, and over-seeding, please fill out the form on this page and I can provide you with a free quote and answer any other questions you might have.