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Ornamental Grasses Demystified

June 17, 2016

Choosing the perfect ornamental grasses for your garden can be challenging for a number of reasons. In fact, while some plants may have the word grass in their name, they aren’t actually grasses.  Instead, they may be sedges, rushes, lilies or any number of other non-grass plants. And, while there’s a grass or grass-like plant to fit just about any environmental garden challenge, determining the right one for your spot may be overwhelming.

Black Mondo Grass flower

Black mondo grass (Ophiopogon planiscapus ‘Nigrescens’) is actually more closely related to asparagus! It has the fun texture of ornamental grasses & unique black coloration, but it isn’t a grass. It spreads slowly in the garden & tends to play nice with others. The showy flowers are a big hint that it isn’t a true grass.

In the world of grasses and grass-like plants, there’s much to choose from. Some are evergreen. Some have showy flowers. Some need deep shade. Some want hot, dry sunlight. Others, like it soggy — seasonally or always. Many will rot in wet. And, many can be weedy and even invasive. So, how to choose?

There’s a great saying that can be helpful if you’re trying to determine if the plant you’re considering is or isn’t a grass:

Sedges have edges. Rushes are round. Grasses are hollow up from the ground/have elbows down to the ground.

Carex testacea

Orange sedge, Carex testacea, has great evergreen texture for dry, sunny gardens. It has slightly sharp edges, which helps identify it as a sedge. It grows in a softly textured mound but may self-seed in the garden. It thrives in hot & dry. The center can rot out over time, especially in a wet winter. Just dig those up & replace’m with a volunteer seedling you fine elsewhere in your garden!

While this old saying may be helpful, it isn’t always going to help you categorize a plant you’re considering.

Junius effuses

Rushes typically have distinctively round blades like this – Juncus effusus, or common rush. It will readily self-seed into your soggy or seasonally soggy garden spots & it can be tough to dig out.

For instance, recently we were trying to figure out whether a plant growing in our pond was good or potentially bad. Identifying it was our first step in understanding whether or not it was the right plant in the right place.

Dragonfly nymph on water plant

Sedges have edges? So does that tell us this flat, not-round blade belongs to a sedge? It certainly supports Dragonfly nymphs grows well in wet!

The plant clearly thrives in very wet conditions, which can work well for many rushes and sedges. It appears to have flat, rather than round, leaves with edges, which indicates a sedge. And, it doesn’t have a showy, lily-like flower, so lilies are out. But, the blooms in clusters at the tips look more rush than sedge, so what is this?

Flora in a pond

Notice the plant in the foreground above. It has strappy, flat foliage & brown inflorescence clusters at the tips of rounded shoots. What is it!?

After doing some online research and digging through a few native plant, pond and grass/grass-like plant books, we were still stumped. So, we put the images out to several co-horts to help us with identification. Fortunately, one friend who had fallen in love with this plant’s little brown tufts remembered that it’s some kind of rush. With that information in hand, we dug back into our resource library and were able to determine that despite having flat leaves with edges, this is indeed the native plant Juncus ensifolius, also known as the sword-leaf rush.

There’s the point of confusion called out in the plant’s common name: sword-leaf! While the interior spike on which the blooms grow is round, what’s most apparent are the flat leaves with edges, not unlike the Schizostylis lily below, which isn’t a grass, sedge or rush!

Schizostylis coccinea

Many flowering plants like this Schizostylis are used in garden designs for both showy flowers & strappy, grass-like foliage. It will readily spread its roots far & wide in the garden in relatively neat clumps.

The good news is that with a bit of digging and help from your friends, getting to know a mystery plant isn’t impossible. The other good news: the mystery plant in our pond is a native plant meant to live in our wetlands — much like plain old common rush that may not have a showy flower, but thrives in soggy spots where many other plants will simply rot.

Junius effusus blooms

Common rush, Juncus effusus, loves soggy spots and often appears in wetlands. It has clusters of brown inflorescences at the tips.

And, let’s not forget those true ornamental grasses! One of our favorites in Asian-influence gardens and shady spots is Japanese forest grass. While it’ll take some sun, it performs best when protected from hot, burning late day summer sun. This beauty is herbaceous, disappearing into the ground for winter, but it’s soft texture and golden brilliance is unbeatable. Be forewarned: dogs and cats both love to chomp on it, but so far it appears our deer aren’t interested in it at all!

Japanese forest grass & astilbe

Hakonechaloa macra ‘Aureola’ pairs beautifully with pink astilbe under a Japanese maple near a stream in eastern morning light.

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