what weeds grow in winter

Spring is just around the corner. Before long you’ll be sowing grass seed, applying fertilizer, and mowing the lawn! To return your lawn to a thick, healthy state, March is the time to begin controlling pesky winter weeds currently taking over your lawn, and preventing summer weeds.

Winter weeds typically flower in March, but can start blooming in February if temperatures are warm! Regardless of when they bloom, you can stop them dead in their tracks with the right control product.

We really like Speed Zone as it contains the same three active ingredients as the other products, but also has Carfentrazone, which makes it work faster and be effective at lower temperatures. Speed Zone also has a two-week waiting period before reseeding the lawn, compared to the three-week waiting period that most of the other products require. This allows you to get started on your overseeding project sooner so that you will be growing thick and healthy turf.

Products to Control Winter Weeds.

Two of our recommended products for Trimec Speed (a new product from Gordon’s for residential use, comparable to Speed Zone, their commercial product), and Bonide Weed Beater Ultra. Generally speaking, liquid weed killers are ideal for controlling actively growing weeds because they typically provide better surface area coverage than granular products. Plus, since they are applied as a spray, they can be turned on or off as needed, limiting waste or overuse.

Winter weeds include chickweed, bittercress, henbit and deadnettle, as well as perennial weeds, such as clover, dandelion and wild violets. These winter weeds actually germinate in late September and early October, but they often go unnoticed in the fall when they’re just young seedlings. They overwinter as a small rosette, and come spring they are ready to strike with a vengeance!

Most winter annuals can be controlled with just one application of weed killer. However, because perennial weeds live year-to-year with an established root system, some of them may be more difficult to control than others. Clover, for example, can typically be controlled with just one application, while others, such as wild violet, may take several applications to effectively control.

Regardless of the weed control product you use, none of them will hurt your lawn if they’re used as directed. Be sure to treat any existing broadleaf weeds in the lawn now, so that you’ll be ready to start building a beautiful new lawn from a clean slate.

Time of year: The seeds of henbit sprout in the fall or early winter. When temperatures start to warm in the spring, henbit will grow vigorously and become noticeable in the lawn. In mid-spring, the flowers form. The henbit then produces seeds and dies as the temperatures start to get hot in early summer.

Remember that a healthy, dense lawn is the best method for preventing winter weeds. Proper mowing height, appropriate watering and professional fertilization are the best defenses against these weeds. Having your lawn treated during the fall can prevent all of these winter annual weeds from showing up in the first place in warm season lawns. In Fescue lawns we focus on the broadleaf winter annuals with our first two applications of the year.

Time of year: Poa Annua is a cool-season grass weed that starts germinating in late summer or fall as soil temperatures fall below 70 degrees Fahrenheit. It continues to germinate throughout winter, allowing several flushes of germination at any one site throughout the season.

Henbit.

Damage: Like other mints, deadnettle is an aggressive grower that spreads like wildfire anywhere it can get a foothold. Getting rid of deadnettle weeds is much more challenging than dealing with many other annual weeds. This is because they tend to go to seed before mowing season even begins.

Prevention/Treatment: To prevent this weed in a residential lawn, cultural practices to develop a dense, aggressive turf may help to hinder its invasive qualities. This includes proper mowing and watering,

What it is: Poa annua, also known as annual bluegrass, is an annual weed that is commonly found in lawns but can be found in gardens as well. The identifying characteristic of Poa annua grass is the tall tasseled seed stalk that will typically stand up above the rest of the lawn.

Prevention/Treatment: A good defense against future henbit problems is to grow a thick lawn so weeds do not have any room to grow. It’s important to find and control the henbit before it flowers. This will prevent the plants from producing and releasing seeds. If you wait until after it flowers, you may be dealing with it for several years to come.

What it is: Deadnettle is a common annual weed that belongs to the mint family. It forms early groundcover mats with fuzzy, spade-shaped leaves and delicate pink-purple flowers. Deadnettle can be found in lawns, along roads, gardens and meadows. It prefers full sun to light shade in moist fertile soil.

What it is: A broadleaf weed that normally acts as a perennial in the north; however, here, it has the ability to act as a winter annual weed due to our climate conditions.

Time of year: During April and May, populations of hairy bittercress become increasingly visible. This weed prefers a cool, moist soil and is most prolific after early spring rains.

Poa Annua.

Prevention/Treatment: A primary method of control is preventing new infestations by having your lawn treated with pre-emergents in the fall. Cleaning landscape equipment after use in infested sites can help prevent Poa annua from spreading to uninfected sites. Isolate small areas of infestation until control can be accomplished. Hand pulling or hoeing to remove Poa annua can be effective as long as it is done frequently.

Damage: Henbit will happily take advantage of the thin, moist areas in your lawn, especially those areas that are shaded. Each plant can produce up to 2,000 seeds that can take root and keep it coming around for years.

Damage: Mouse-ear chickweed can form dense, mat-like patches that can crowd out desirable turfgrass.

Damage: This pesky weed can displace grass as it grows in the lawn. Its extensive seed expulsion causes this weed to spread quickly through the lawn and garden in spring.

Damage: Poa annua grass is typically a problem in the lawn because it dies back in hot weather, which can make unsightly brown spots in the lawn during the height of summer. It also thrives during cool weather, when most lawn grasses are dying back, which means that it invades the lawn at these susceptible times.

Deadnettle.

While warm-season lawns are dormant in the winter, many weeds are just starting to become active. These weeds are known as winter weeds. They can be annual, biennial or perennial in regards to life cycles, and be very difficult to control. Annual winter weeds germinate in the fall and winter and grow actively in the spring. After they flower in spring, they die and disappear before the summer. But only to return in fall or winter when new seeds germinate.

Prevention/Treatment: Encouraging good grass growth is important to preventing hairy bittercress invasions. Pulling out hairy bittercress can often leave the roots behind and is usually most effective with young plants. It’s best to use a weeding tool to dig down and around the taproot to get all the plant material out of the ground. Post-emergent weed control is the most effective and long-term solution.

Time of year: Deadnettle is a winter annual weed that primarily emerges in the fall. But the flowering and seed set beginning in early spring. Plants die with hot, dry weather in late-May and June.

What it is: Hairy bittercress is an annual winter weed. The plant springs from a basal rosette and bears 3-9″ stems with leaves that are alternate and slightly scalloped. Tiny white flowers develop at the ends of the stems and then turn into long seed pods.

Prevention/Treatment: Growing a thick, healthy lawn is the first line of defense against these mint cousins, since the grass will easily outcompete the weeds for nutrients and growing space. One or two deadnettle weeds popping up in the lawn can easily be plucked by hand and disposed of as soon as they appear, but a larger population requires a more complicated solution.

What it is: Henbit is a sparsely hairy winter annual with greenish to purplish, tender, square stems. It is often found under trees and shrubs where grass has a hard time growing.

Photo: OSU Bugwood.

Photo: OSU Bugwood.

Purple deadnettle, a winter annual broadleaf weed, germinates from seed, grows and dies in less than a year. The nectar of purple deadnettle is attractive to bumble bees, honey bees and digger bees, a group of large bees that nest in the ground, according to Michigan State University Extension. If you are trying to eliminate it with a herbicide, it is best controlled in fall or when actively growing.

1. Annual bluegrass.

The best defense against henbit is to properly maintain turfgrass. This includes selecting the right species for the location and usage, plus proper cultural practices including mowing, fertility, irrigation and aeration.

Photo: Brian Stiehler.

Photo: Dr. Aaron Patton.

One of the most persistent weeds, annual bluegrass, Poa annua , is also one of the most common weeds in the United States. Leaf blades that are crinkled part way down are a key characteristic of annual bluegrass, according to the University of California, Statewide Integrated Pest Management program.

Read more about Poa annua on golf courses: Controlling Poa annua With The Right Tools.

Winter annuals germinate and develop in the fall, overwinter as plants, mature in the spring, flower, set seed and then die during the summer. Annual bluegrass is one of the most common winter annual grassy weeds in turf. Henbit, purple deadnettle and common chickweed are other examples of winter annual broadleaves. Here, we’ll review four common winter annual weeds, plus provide tips on how to control their growth.

Common chickweed is a prostrate, winter annual that’s found throughout North America. Common chickweed mainly blooms February to September. The small flowers have what appear to be 10 petals, but are really five deeply-cut white petals. The best time to control chickweed is in the fall or spring.

3. Purple deadn ettle.

2. Henbit.