While there are many different types of grassy weeds, these four are most prominently found on your lawn. One of the main challenges of working with grassy weeds is that they all share very similar characteristics to regular turf grass. This means the first step in successfully getting rid of grassy weeds in Canada is proper identification.
Grassy weeds, including quack grass, crabgrass, bluegrass and nutsedge compromise your soil's integrity, decreasing the availability of nutrients and ultimately leading to an unhealthy, nutrient-poor soil that is susceptible to more weed invasion. Even though these grassy weeds may not look threatening, failing to treat them right away can damage your lawn indefinitely.
Grassy weeds are different from other weeds as they are a C3, instead of a C4 plant. This changes the way they perform photosynthesis, or the way they extract nutrients from their environment. This means that they are ultra-competitive and will do anything to survive and thrive on your lawn.
Grassy weeds, thanks to their ultra-competitive nature often grow at a much faster rate than turf grass. If you notice a certain area of your lawn is growing faster than the rest, this area could be grassy weeds.
Grassy weeds are typically slightly wider than turf grass, and may grow in a characteristic star pattern, with new shoots sprouting from the middle. Some grassy weeds may also produce small, flowering heads that are not produced with turf grass. Grassy weeds may also make part of your lawn appear discolored, as turf grass has a consistent color while grassy weeds can have yellow to blue tinges in color.
Follow the rest of this guide to understand what type of grassy weed you have, and the difference compared to grassy turf.
Quack grass is a cool season grass and therefore very common in Canada. It’s very common amongst farmers and is estimated to effect up to 50% of farmland. It can spread by seed and by the root system, a mature plant can yield up to 25 seeds.
It’s extremely important to pull quack grass as soon as you notice it and pull out the white root system as well. Quack grass grows at a speed of 2.5cm per day.
Mature plants are very tall - reaching up to 3 feet
Crabgrass is a common grassy weed in Canada. Crabgrass primarily spreads by seed, so the ultimate goal in management of crabgrass is seed control. By reducing the viable seed supply, it will decrease the ability of the seeds to establish themselves year after year after year. It is also important to note that crabgrass cannot be eliminated in one season, and requires the establishment of a healthy, thick turf grass to outcompete the weed.
Leaf blades are usually 1/4 inch thick, much thicker than turf grass
Grow in a star-shaped pattern, with new shoots growing from the middle
Will send out solons, or "crab legs" to acquire more territory
Annual bluegrass is a common perennial grassy weed. The weed is adapted to cool-seasons and well-watered sites. Annual bluegrass is able to resist low-mowing heights of <1 inch. This perennial grassy weed typically starts to germinate in late summer/fall when temperatures fall below 21 degrees C and will continue to germinate throughout the winter months.
Leaf blades have characteristics "boat-shaped" tips
White, fuzzy seed heads typically appear in spring
Mature plants may grow up to 12 inches tall
Nutsedge is not a grass, but classifies as a sedge. Due to its similar identifying characteristics and weed management control, it is often grouped with grassy weeds. This perennial plant reproduces by tubers that are often found in the top 6 inches of soil. The tuber must be removed to control weed growth; therefore, it is recommended to hand-pull the weed once every 2-3 weeks to starve the tuber nutrient supply.
Often thicker & stiffer than turf grass
Produces light brown "wheat looking" flowers with seeds
Blades are arranged in a trio at the base of the plant, and then grows in sets of two
Grassy weeds start to germinate around 13 degrees Celsius, especially when it’s been that temperature for 5 days straight. It’s important to catch grassy weeds early on as some of them, especially crabgrass, can spread up to 150,000 seeds.
Note: Pull weeds once every 2-3 weeks to starve the nutrient supply
A healthy and thick lawn is the best defense in preventing grassy weeds. The thinner the lawn is, then less shade your soil gets, and since grassy weeds thrive in warm soil temperatures. A thick lawn provides good shade for the soil and keeps the soil temperatures cool, which prevents grassy weed germination. Additionally, a thick lawn will choke out and out-compete any other unwanted vegetation; including grassy weeds but not limited to broadleaf weeds as well.
The longer the grass is, the more shade it will give to the soil. If you scalp your lawn too short (less than 2.5”) that can create multiple problems including grass weeds and having your lawn burning out. Keep your mowing height between 2.5” and 3.5” for best results.
Once again, the best defense against weeds in general is having a healthy and thick lawn. The regular maintenance and yearly fertilization and weed control is crucial to keeping your grass healthy. Not fertilizing for one year can cause major lawn damage if not addressed.
The best practice for a healthy lawn is to water 2-3 times a week, but water for longer periods. The average lawn needs one inch of water per week. It’s better to do a half-inch watering session twice per week then ten periods of 1/10 inch watering sessions.
In the United States, pre-emergent herbicides, or herbicides that effectively kill the seeds and roots of grassy weeds before they form are approved for use. However, pre-emergent including prodiamine or barricade are not registered in Canada, meaning lawn care companies do not have access to them.
In Canada, management of weeds requires an aggressive and proactive approach to ensure your lawn is extremely healthy, thick, and lush. This increases the competition of your lawn, ultimately making it hard for weeds, including grassy weeds, to establish themselves and take over your lawn.
There isn’t a one-size fits all for the management of grassy weeds, there are steps and strategies that you can implement today to help you manage your grassy weeds.
If quack grass is outside your lawn, you can use a vegetation control for it such as RoundUp or concentrated vinegar. If it’s within your lawn, those products will kill all the grass around it, so you need to be careful in choosing a product.