8 pointers for choosing and planting ornamental grasses

June 30, 2015

Grasses aren't just for lawns anymore. Ornamental grasses come in an array of sizes, forms and colours, and they can adapt to just about any growing conditions.

8 pointers for choosing and planting ornamental grasses

Ornamental grasses in your garden

  • Low growers are marvelous in masses as a no-mow lawn substitute, or as edgings around beds or along paths.
  • Enjoy single clumps of large grasses as eye-catching accents or multiples as screening. They look great mixed with flowering plants in beds, too!

1. Explore your options

The key to growing gorgeous grasses is choosing those that are naturally adapted to the site where you'll plant them. Otherwise, they'll take more work to maintain, be more prone to problems and never look their best.

  • Sun lovers, such as miscanthus and pampas grass (Cortaderia), tend to have weak stems and need staking if they get too much shade.
  • Sedges (Carex spp.) and other ornamental grasses that prefer shade can turn crispy brown in sun-baked sites, even if you give them lots of extra water.

2. Clump-forming options enhance flower beds

For flower beds, stick with ornamental grasses that are described as clump forming.

  • These well-behaved grasses form tidy mounds or tufts that expand gradually over time, but basically stay in one place.
  • That means you can pair them with flowering annuals, bulbs and perennials without fear that they'll crowd out their more delicate companions.
  • Examples of clumpers include fescues, miscanthus and feather reed grasses (Calamagrostis spp.).

3. Choosing warm-season grasses

You'll often see ornamental grasses described as warm season or cool season.

  • Warm-season grasses, such as miscanthus (Miscanthus spp.) and fountain grasses (Pennisetum spp.) are slow to sprout in spring, but they shoot up once the weather heats up, producing their flowers and showy seedheads in late summer.
  • They're fantastic for adding autumn interest to your landscape.

4. Choosing cool-season grasses

Cool-season grasses, such as fescues and blue oat grass (Helictotrichon sempervirens), do most of their growing when temperatures are below 24°C. During the dog days, they slow down or stop growing altogether.

  • Enjoy them with spring bulbs and early perennials, then combine them with later-blooming plants to take over the show in summer and fall.

5. When to plant grasses

Timing is everything.

  • Early spring is the best time to plant warm-season grasses so they'll have time to get their roots down before their summer growth spurt begins.
  • You can plant cool-season grasses just about any time the ground isn't frozen, but early-spring planting usually works best for them, too.

6. Weed the grass site

  • Before you plant, weed the area thoroughly.

It's especially important to remove any turf or weed grasses. Otherwise, they can grow into your ornamental grasses and you'll have a tough time getting the bad grasses out without pulling out the good grasses as well!

7. Keep ’em lean

  • Ornamental grasses typically grow best in average garden soil, so don't put a lot of work into preparing a perfect planting site.

Rich soil leads to lush growth, which can lead to disease problems or cause weak stems that need staking. It's fine to add a few handsful of compost to the planting hole, but avoid using manure or high-nitrogen fertilizers.

8. Cutting back ornamental grasses

Warm-season grasses usually turn tan or coppery by late fall, but their foliage often stays good-looking well into winter.

  • To tidy them up in spring, use hand shears to snip small grasses back to about five centimetres or a pruning saw.
  • Electric hedge shears work better for cutting large grasses to about 15 centimetres above the soil.
  • Wear gloves while working with grasses, because their leaves can have sharp edges.
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