Ornamental grasses have become very popular to use in gardens and landscape. It’s a good idea to understand how they grow which in turn will help you understand how to use them and often avoid disappointment or frustration.
Grasses are broken down into two classes: Cool season and Warm season. Grasses start to grow based upon temperature. Some grasses will start to grow in early spring when temperatures are still cool and others will wait until the soil is warm and temperatures are more stable.
Cool Season Grasses
Cool season grasses will start to grow early in the spring and may even remain semi-evergreen over the winter. Cool season grasses also seem to do better and have better foliage quality when temperatures are cool or if they are given sufficient water during drought periods. If they are not watered during drought, they tend to go dormant resulting in brown foliage.
This is my front yard gardens, the white arrow show a Karl Foestser, and so is the one across from it. This is a fabulous grass, not invasive, grows early in season, and if not in full sun will look beautiful all summer long.
Cool season grasses may require more frequent division to keep them healthy looking and vigorous. If not, they tend to die out in the center. For the ones that remain semi-evergreen, you should only cut off the brown or winter injured foliage in the spring. Some of the more popular cool season grasses include, Karl Foerster (Feather Reed), Fescues, Blue Oat Grass (Helictotrichon), Tufted Hair Grass (Deschampsia), and Autumn Moor Grass (Sesleria).
Warm Season Grasses
Warm season grasses will do better during the warmer parts of the year, they also remain good looking even when temperatures are high and moisture is limited, making them drought tolerant. Warm season grasses will not start growing until the weather becomes stable and the soils warm.
Northern Sea Oats in another photo of my front garden by the black arrow. It is a compact grass that does very well in shady or partial sun areas. BUT it is a HEAVY reseeder. So you will find young seedling popping up all over. You can see the dappled shade in my front garden, and I think this is proof a partial shade garden can be as beautiful with various textures and shapes.
The previous seasons growth usually browns out in the fall which requires you to cut back the grass to about 4-6 inches in the spring. Warm season grasses usually do not require as frequent division as cool season grasses. Some warm season grasses include Northern Sea Oats (Chasmanthium), Japanese Silver Grass (Miscanthus sp.), Hardy Pampas Grass (Erianthus), Perennial Fountain Grass (Pennisetum), Switch Grass (Panicum) and Prairie Cord Grass (Spartina).
Understanding the growth habit of the grass will also help your to before buying/planting. Grasses can be either clump forming or rhizome forming ( aka: running grass). The clump forming will grow in very nice, neat mounds or clumps. They tend to mix very well with other perennials and will not become invasive. They will increase in girth slowly over time.
The rhizome forming grasses spread by underground stems and can become very aggressive and invasive. These grasses have their place but it may not be in a well-tended perennial border since they can soon take over an entire area. Before selecting a grass, be sure to understand how it grows so you won’t be planting a future problem. Some attractive but aggressive grasses include Blue Lymegrass, Cordgrass, and Ribbon grass.
I hope this post will help you determine which grasses are right for your garden.
What grasses do you have in your garden?