Some Ontario weeds can invade and take over your lawn if not proactively controlled. These difficult weeds are resistant to fiesta weed control and adapt to challenging growing conditions. In this post, we’ll discuss how to address the toughest weeds to control in Ontario.

Shade Tolerant Ontario Weeds

These weeds can be particularly challenging because turfgrass is not a particularly shade tolerant plant. These difficult weeds can thrive in areas of your lawn that are shaded and even prefer the shade.

Creeping charlie  (ground ivy)

Is a low-growing plant with kidney-shaped leaves and a distinct minty scent. It spreads via stolons (above-ground runners) and can root at the nodes, making it difficult to control. Creeping Charlie can tolerate a range of growing conditions, including shade, wet soil, and low fertility. Managing creeping charlie is difficult, raking out clusters and overseeding with quick establishing ryegrass is recommended.

Wild violets

This weed has heart-shaped leaves and produces small purple or white flowers in early spring. It spreads via rhizomes (underground stems) and can form dense canopies in shaded areas that completely shade out grass. Wild Violets can tolerate a range of growing conditions, including shade, moist soil, and low fertility.

Oxalis (woodsorrel)

Often mistaken for clover in the lawn. It produces small yellow flowers and spreads via seed and underground bulbs, which can remain dormant for years before sprouting. Oxalis can tolerate a range of growing conditions, including shade, dry soil, and low fertility.

Wood sorrel isn’t an aggressive spreader and can usually be managed with a combination of regular mowing and overseeding your lawn.

These weeds are particularly difficult to control because they can spread rapidly and grow vigorously in shaded areas. What makes these weeds even more difficult is they are all resistant to fiesta weed control and require several applications per year to manage.

Recommendations

To address these weeds, one of the best strategies is to overseed your lawn with grass that is more shade tolerant, such as fine fescues. This will help to create a thicker, healthier lawn that can better compete with these weeds. Additionally, proper landscape design can help to minimize shaded areas, such as pruning trees or shrubs to let in more sunlight.

Watering

It’s especially important to ensure the lawn is properly watered in the shade. Lawns can be overwatered in the shade leading to the development of mosses. However, underwatering in the shade is just as bad. Shaded lawns will suffer more from drought than sunny lawns because water is essential for your lawn’s rigidity and photosynthesis. Because shaded lawns are producing less sugar they become impaired by slight even reductions in photosynthesis

Annual Ontario Weeds

Annual weeds can be particularly challenging because they appear while lawns are dormant or in slow growth periods. These weeds can quickly take over your lawn, and they can be difficult to control once they have established themselves.

Knotweed

This weed has small, oval-shaped alternating leaves and produces tiny pink or white flowers in late summer. It only spreads via seed and can grow rapidly in areas of disturbed soil. Knotweed is particularly tough because it can tolerate a range of growing conditions, including drought, heat, soil compaction and low fertility.

Crabgrass

This weed has wide, flat leaves and produces seed heads that resemble crab legs. It spreads via seed and can grow rapidly in areas of disturbed soil. Crabgrass is particularly tough because it can tolerate extreme growing conditions, including heat, drought, and compacted soil.

Crabgrass has an adaptation that allows it to survive temperatures unsuitable for cool season grasses of Canada. This adaptation is known as C4 photosynthesis.

Goosegrass

This weed has long, flat leaves and produces seed heads that resemble a comb. It spreads via seed and can form dense clumps in lawns and gardens. Goosegrass is tough because it can tolerate a range of growing conditions, including shade, heat, drought, and low fertility.

Recommendations

To address these weeds, overseeding your lawn with grass that can compete with these weeds is key. Additionally, applying a pre-emergent herbicide can help to prevent the seeds of these weeds from germinating. However, it’s important to apply pre-emergent herbicides at the right time of year to be effective.

Bunch-grass Ontario weeds

These weeds can be particularly challenging because they are immune to fiesta weed control. Fiesta weed control is an iron-based herbicide used to control weeds in Ontario lawns but is not effective against grasses.

Dallis grass

This weed has long, flat leaves and produces seed heads that resemble a spider web. It spreads via seed and can form dense clumps in lawns. Overseeding with creeping rye grasses that can compete with this weed is important. Dallis grass is considered as invasive.

Quack grass

This weed has long, flat leaves and produces seed heads that resemble wheat. It spreads via rhizomes that secrete a substance that is toxic to surrounding plants. Quackgrass is tough because it can tolerate a range of growing conditions, including shade, drought, and low fertility.

Quack grass is considered as invasive. It is crucial to dig quack grass out and re-seed the area with new topsoil.

Coarse fescue

It spreads via seed and can form clumps in the lawn. Bunch Fescue is particularly tough because it can tolerate a range of growing conditions, including shade, drought, and low fertility. Fun fact: Bunch Fescue is often used in ornamental grass gardens and is popular for its attractive foliage and seed heads.  Coarse fescue in the lawn can indicate your soil is prone to drought.

Recommendations

For these unmanageable grasses, it’s best to manually remove large bunches and clusters and reseed them.  Overseeding in this case is not going to produce satisfactory results.

Other Ontario weeds Immune to Fiesta Weed Control

Rough Bluegrass

This grass produces a fine lighter colored turf and spreads via stolons and seed. It can tolerate a range of growing conditions, including shade, wet soil, and low fertility. Rough Bluegrass is tough because it can form dense mats in lawns and gardens, making it difficult to control.

Bentgrass

This grass is often used on golf courses and produces dense, fine turf. It spreads via stolons and rhizomes forming a thick mat over the soil. Bentgrass is particularly tough because it can spread rapidly and recover quickly from damage. Bent grass tolerates soggy soil and can be found in ditches and the drains of your eavestrough

Bentgrass will usually appear lighter in color than the rest of your lawn and is quicker to brown in drought conditions. Fun fact: Bentgrass is a popular choice for golf courses because of its tolerance for short mowing and its ability to recover quickly from damage.

Recommendations

To address these weeds, overseeding is important. However, it’s more important to address the growing conditions. Bentgrass and rough bluegrass are often indicators of soggy soil conditions.

Weed control summary

Managing weeds in your lawn can be quite a challenge, especially in Ontario where tough weeds abound. However, there are effective steps you can take to overcome this issue. Firstly, you can improve the quality of your lawn by overseeding it with high-quality grass seed. Additionally, you can maintain healthy soil and address any physical problems that may be contributing to weed growth in your landscape.

By following these steps, you’ll be well on your way to successfully managing even the most stubborn weeds in Ontario.