Choosing the Perfect Ornamental Grasses for Ottawa Clay

Conquering Clay with Graceful Grasses

Ottawa’s heavy clay soil can be a challenge for gardeners. It’s dense, often poorly drained, and can bake hard in the summer sun. But don’t despair! Ornamental grasses are surprisingly adaptable, and many thrive even in our tricky clay conditions. This guide will help you select the best ornamental grasses to add texture, movement, and beauty to your Ottawa garden, even if you’re battling clay in Manotick or Nepean.

Why Ornamental Grasses are a Clay-Buster’s Best Friend

Unlike some delicate plants, many ornamental grasses have deep, fibrous root systems that actually *improve* clay soil over time. These roots break up compaction, create channels for air and water, and add organic matter as they decompose. This means that, paradoxically, planting grasses can help solve the very problem (clay soil) they are thriving in! Plus, they offer a wide range of heights, colors, and textures, providing visual interest throughout the year.

Top Ornamental Grass Picks for Ottawa Clay

Here are some of the best ornamental grass choices for our region, specifically selected for their tolerance of clay soil:

1. Switchgrass (Panicum virgatum): A North American native, switchgrass is incredibly tough and adaptable. It comes in a variety of cultivars, from the upright ‘Shenandoah’ (red-tinged foliage) to the blue-green ‘Heavy Metal’. Switchgrass provides excellent winter interest, with its seed heads persisting through the snow. It tolerates wet clay soils well. This is perfect if dealing with heavy clay soils in areas like Osgoode.

2. Feather Reed Grass (Calamagrostis x acutiflora ‘Karl Foerster’): This is a classic choice for a reason! ‘Karl Foerster’ is a sterile hybrid, meaning it won’t self-seed aggressively. It offers a strong vertical accent and beautiful, feathery plumes that emerge in early summer. It prefers full sun and can tolerate moderately heavy clay. Gardeners in Greely will love this one for its four-season interest.

3. Big Bluestem (Andropogon gerardii): Another North American native, Big Bluestem is known for its blue-green foliage that turns a stunning reddish-bronze in the fall. It’s a tall grass, reaching up to 6 feet, and provides excellent habitat for birds. It can handle dry, clay soil and even drought conditions, once established. The Lady Bird Johnson Wildflower Center offers more information on Big Bluestem.

4. Indian Grass (Sorghastrum nutans): Indian Grass is another tall, native grass with beautiful, golden-bronze plumes in late summer and fall. It’s very adaptable to different soil types, including clay, and prefers full sun. Its fall colour is stunning.

5. Little Bluestem (Schizachyrium scoparium): A shorter option compared to Big Bluestem, Little Bluestem offers beautiful blue-green foliage that turns shades of red, orange, and purple in the fall. It’s very drought-tolerant once established and thrives in well-drained clay soils. Consider using the right mulch to help retain moisture. The ‘Standing Ovation’ cultivar is particularly upright and colorful.

These options are generally easy to find at local garden centers in Ottawa and surrounding areas like Richmond. You can also check out places like the Ottawa Valley Rock Garden and Horticultural Society for plant sales and advice.

Planting and Caring for Ornamental Grasses in Clay Soil

While these grasses are tolerant of clay, proper planting and care will ensure they thrive:

1. Planting Time: Spring or early fall is the best time to plant ornamental grasses in Ottawa.
2. Soil Amendment: As mentioned, amend the planting hole generously with compost. You can also add a small amount of granular fertilizer formulated for ornamental grasses.
3. Digging the Hole: Dig a hole that is twice as wide as the root ball and just as deep.
4. Planting Depth: Plant the grass at the same depth it was growing in the container.
5. Watering: Water deeply after planting, and then regularly, especially during the first growing season. Once established, most of these grasses are quite drought-tolerant.
6. Mulching: Apply a layer of organic mulch, such as shredded bark or wood chips, around the base of the plant to help retain moisture, suppress weeds, and regulate soil temperature. Remember to keep the mulch away from the crown of the plant.
7. Fertilizing: Ornamental grasses generally don’t require a lot of fertilizer. A light application of a balanced fertilizer in spring is usually sufficient.
8. Dividing: Most ornamental grasses benefit from being divided every few years. This helps to rejuvenate the plant and prevent it from becoming overcrowded. The best time to divide grasses is in early spring, before new growth emerges.
9. Cutback: Leave the foliage standing over winter to add interest to your garden and provide habitat for wildlife. In early spring, before new growth begins, cut back the old foliage to just a few inches above the ground.

Designing with Ornamental Grasses in Ottawa

Ornamental grasses can be used in a variety of ways in the landscape. Here are a few ideas:

• Mass Plantings: Create a dramatic effect by planting large drifts of a single type of grass.
• Mixed Borders: Combine grasses with flowering perennials and shrubs for a dynamic and textured look.
• Focal Points: Use a single, striking grass as a focal point in a garden bed.
• Containers: Some smaller grasses, like Little Bluestem, work well in containers.
• Screening: Taller grasses can be used to create a privacy screen or to soften harsh architectural lines.
• Erosion Control: The deep roots of ornamental grasses make them excellent for stabilizing slopes and preventing erosion, a useful feature in areas like Winchester with variable terrain.

Remember to consider the mature size of the grass when choosing its location. You don’t want it to overcrowd other plants or block pathways. If you’re unsure, our garden installation services can help.

Addressing Clay Soil Challenges

While the grasses listed above are clay-tolerant, here are some extra tips for dealing with Ottawa’s heavy clay:

• Improve Drainage: If you have standing water after heavy rain, consider installing a drainage swale or rain garden to help redirect the water.
• Amend Regularly: Continue to amend your soil with organic matter, such as compost, over time. This will gradually improve its structure and drainage.
• Avoid Compaction: Minimize foot traffic on areas with clay soil, especially when it’s wet.
• Consider Raised Beds: For particularly challenging areas, consider building raised beds filled with a better-draining soil mix. This can be a good option for smaller gardens or for growing plants that are less tolerant of clay.

Dealing with clay soil takes patience, but the rewards are worth it. By choosing the right plants, like the ornamental grasses discussed here, and implementing good gardening practices, you can create a beautiful and thriving garden in Ottawa, even in areas like Kars or Vernon where clay is prevalent.

Frequently Asked Questions

What if my clay soil is really, really bad?

Even the toughest grasses need a little help to get started. Amending the soil with a generous amount of compost is crucial. You can also consider incorporating some coarse sand or gravel to improve drainage, but focus primarily on adding organic matter.

Can I plant ornamental grasses in the shade?

Most ornamental grasses prefer full sun (at least 6 hours of direct sunlight per day). However, some, like Northern Sea Oats (Chasmanthium latifolium), can tolerate partial shade. Check out our post on shade gardens for more shade-tolerant options.

How do I prevent ornamental grasses from spreading too much?

Choose clumping varieties rather than running varieties. ‘Karl Foerster’ feather reed grass is a good example of a clumping grass. Divide grasses every few years to keep them contained. Also, be sure to deadhead (remove spent flower heads) before they go to seed.

Are ornamental grasses deer-resistant?

While no plant is completely deer-proof, many ornamental grasses are considered deer-resistant. Deer tend to avoid plants with coarse or sharp-edged foliage. Switchgrass, Big Bluestem, and Little Bluestem are generally good choices for areas with deer pressure.
Homeowners in areas like Kenmore may find this information helpful.