Ornamental Grasses
The Good, the Bad, the Ugly

Having used ornamental grasses for their glorious textures, complementary flowering, colors and forms for most of my 43 years of landscape designing, I have a love-hate relationship with them.
We are not talking about lawn turf grasses, as that is an entirely different discussion.
While most landscapers & gardeners commonly lump sedges and rushes into grasses, sedges and rushes will be a discussion of a different article.

Suffice to say most grasses have round stems -- and that is what we are discussing.
Grasses have been around for about 66,000,000 years and have evolved to around 12,000 species and countless varieties.  Dinosaur coprolites contain grass-like phytoliths: yes, dinosaurs ate grasses. We have about 1500 species in North America.

Grasses are monocots, which means that as they emerge from the soil, a single cotyledon ‘leaf’ is formed. In dicotyledons, two leafy cotyledons are formed.  Corn is a monocot and beans are dicotyledons.
By far, most of the grasses we raise are grains such as: wheat, oats, barley, rice, millet, sorghum, fonio, rye, and corn, and these are annuals. The commonly used grasses in our gardens are perennials.
Ranging in height from 1 inch to over 50 feet, grasses inhabit nearly every habitat on the planet.  Poa annua - Annual Bluegrass or Annual Meadowgrass, has now made its way to Antarctica and is one of the most invasive species of grass on the planet.

Lawn/turf grass, typically made up of Poa pratensis, Bluegrass, is generally considered not to be native to the United States, although some botanists claim that there may be some native patches in some remote mountain meadows in western United States.  Nevertheless, it is not native to the Eastern United States.  Bluegrass is a highly invasive species native to Northern Africa and Eurasia.  Many homeowners would never consider using non-native species in their landscapes, yet, are fully happy with the main dominant plant in their landscape being an introduced invasive specis.

Some of the ‘Ugly’ perennial grasses, and most of these are banned, that we have in Wisconsin are:
Arrhenatherum elatius - Oat Grass
Bromus tectorum - Drooping Brome/Cheating Grass
Dactylis glomerata – Orchard Grass
Elymus repens - Quack Grass
Glyceria maxima - Tall Manna Grass
Imperata cylindracea – Japanese Emperor Grass including the red leafed forms
Leymus arenarius – Lyme Grass
Microstegium vimineum - Japanese Stilt Grass
Miscanthus sinensis – Eulalia Grass (the invasive species)
Miscanthus saccariflorus – Silver Banner Grass
Phalaris arundinacea - Reed Canary Grass including the variegated forms
Phragmites australis – Common Reed Phragmites
Spartina anglica - Cordgrass

Many of the above grasses, once inhabiting your garden or lawn, are very difficult to get rid of.
Besides chemically spraying them with grass specific (only kills true grasses) herbicides, such as Fluazifop (Fluazifop-p-butyl) or non-specific herbicides such as Glyphosate, digging them out is the only way to eradicate them.

I am certainly not saying not to plant any of the `Baddest’ grasses for our garden.  Many are some of our most beautiful ornamental grasses.  I just wish to inform you that there is a maintenance issue in that they have a tendency to spread – sometimes invasively – by seed. They often seed into the bed areas in which you planted them and inside your desirable herbaceous perennials such as Hemerocallis-Daylily, Paeonia-Peony and Iris. Once established in the clumps of other plants, they are difficult to eradicate. They are even more difficult to eradicate when they germinate inside other desirable grasses. If they germinate inside non-grass plants, one can always use Fluazifop to control/eradicate them.  However, the only way to eradicate grasses that are invading other grasses is to dig them up, divide them, pick them part, remove the invasive grass, and then replant.  If they germinate in your lawn, you need to manually dig them out or replace the lawn.

Another one of the ways to control the seed germination of desirable ornamental grasses, is to treat the bed or lawn areas with a pre-emergent such as Pre-M, which contains Pendimethalin.  Other pre-emergence on the market may or may not control many of the grass seeds. When treating your lawn for annual grasses such as Digitaria - Crabgrass, you are also treating for the seed germination of many of the ‘Baddest’ grasses.

Some of the `Baddest’ ornamental grasses include:
Andropogon spp. - Bluestem
Bouteloua curtipendula Side-Oat Grama
Briza media – Common Quaking Grass
Calamagrostis arundinacea – Feather-Reed Grass
Calamagrostis brachytricha – Korean Feather-Reed Grass
Chasmanthium latifolium – Wild-Oat Grass
Descampsia cespitosa – Tufted Hair Grass
Hordeum jubatum - Squirrel-tail Grass
Elymus hystrix (Hystrix patula) – Bottle grass
Molinia caerulea – Purple Moor Grass
Panicum virgatum – Switchgrass – Panic Grass
Pennisetum alopecuroides – Fountain Grass
Schizachyrium scoparium – Little Bluestem
Sorgastrum nutans – Indian Grass
Spodiopogon sibiricus – Graybeard Grass
Sporobolus heterolepis – Prairie Dropseed

The `Good’ grasses are those that have a tendency to stay in one place – spreading slowly and typically produce few if any viable seed.  These are typically easy to manage and are very showy. The Calamagrostis hybrids rarely produce seed, but do die-out in the centers after years in the garden. You will need to dig them, divide and replant them every five or so years. If very happy with your perfectly drained soils, Festuca glauca can seed around quite happily. I recommend giving the seedling tufts to you friends. If you are lucky, Hakonechloa will spread by runners, but for most folks, it’s easily controlled. ‘Saphirsprudel’ produces very few seeds if any and is a form that is quite resistant to rust. The species is highly prone to rust that is common in our area. While Miscanthus rarely produces germinating seeds, the non-clumping forms just never know when to stop spreading. However, the clumpers are some of the more desirable grasses we have available for our gardens. They will die out as they slowly spread outward, forming a dead hole in the center. Just like Calamagrostis, you will need to dig them, divide and replant every 7-10 years.

Some of the ‘Good’ grasses for our gardens include:
Calamagrostis x acutiflora - Feather-Reed Grass
Festuca glauca - Blue Fescue
Hakonechloa macra - Hakona Grass
Helictotrichon sempervirens - Blue Oat-Grass ‘Saphirsprudel’
Miscanthus sinensis var. gracilimus - Clump Eulalia Grass

Happy gardening.
Steve Lesch © 3/2016

 


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