Grasses Take The Heat

The intense heat and humidity of summer make us long
for a summer breeze. Nothing compares to the momentary cooling and the beautiful
sound that develops as the air moves through a planting of ornamental grass.

Ornamental grass is a general title given to a group
of plants that are either true grasses or have a grass-like habit such as sedges,
rushes, cattails, and bamboos. Each grass differs in its habit and cultural requirements,
so it is important to select ones that are suitable for the environment we have
to offer.

There are hundreds of grasses available to us today
and they come in all sizes-from those growing only 12 inches tall to many that
grow to over 15 feet in one season. Most grasses prefer a sunny location but there
are a few that grow well in partial shade. And if you have wet soil, dry soil,
or somewhere in between, there are still many for you to pick from.

Miscanthus or maidenhair grass

The first group is miscanthus, also called Japanese
silver grass or maidenhair grass. It ranges in height from 3 feet to over 8
feet in bloom. This warm-season grass prospers in the heat of summer and although
it will flourish in moist soil, it also does well in dry, heavy clay soils that
are predominant throughout this region. What makes this plant so strong also
gives way to its ability to be invasive and naturalize, especially in areas
that are moist. As a general rule I like to plant miscanthus in hot, dry sites
with poor soil. This seems to keep them under control in the garden. Even in
the poorest of sites I have never found it necessary to fertilize a miscanthus
planting.

One of my favorite cultivars is Miscanthus sinensis
‘Morning Light.’ The narrow foliage and predominant white mid-vein give it an
almost variegated appearance. It is also smaller in habit than most miscanthus,
under 4 feet tall, making it suitable for almost any garden or large decorative
container on your porch or patio.

M. sinensis ‘Adagio’ also has narrow foliage and is an excellent bloomer,
with the inflorescence emerging almost red and then turning a light straw. M.
sinensis ‘Variegatus’ has incredible white striped foliage that provides
an excellent contrast for the garden. This particular variety needs to be dug
and divided every 3 to 4 years to keep it full and dense, preventing it from
flopping late in the season in your garden.

Bamboo grass

Pleioblastus variegatus (Arundinaria variegatus),
white striped bamboo, is a medium-sized and moderately invasive bamboo. Under
3 feet tall, the white striped foliage serves as a fabulous groundcover in areas
where it is difficult to get anything to grow. The invasive behavior is easy
to control when planted in poor, dry soil, but watch out if it is moist and
fertile: it can completely overtake your garden. This is another one of my favorite
plants to use alone or in combination in container gardens.

Purple fountain grass

Pennisetum setaceum ‘Rubrum,’ purple fountain
grass, has almost become one of my signature grasses. It provides a whole new
level to my annual garden and container designs. It is always extremely disappointing
to find out that this tropical grass is not hardy in Kentucky. The beautiful
reddish-burgundy leaves gracefully rise up like a fountain. With its foxtail-like
flowers, this grass reaches almost 4 feet tall. Most varieties of fountain grass
are completely hardy in Kentucky, but the purple fountain grass is not. As a
group, fountain grass is not touched by our heat and humidity and prospers in
poor soils. For hardy varieties look for cultivars of Pennisetum alopecuroides.

When to cut

Ornamental grasses should be cut to about 6 inches
above the ground each year to remove the old growth. Some people like to cut
them back in the fall but I like to wait until early March, leaving the foliage
up all winter to enjoy. Bamboos, sedges, and reeds are different and many do
not need to be cut back each year. In a mild winter only a little light pruning
may be necessary to get your ornamental grasses in shape for spring.

Let your imagination take you wherever it wants to
go when deciding what looks good in combination with your ornamental grasses.
I like to use lots of perennials like black-eyed Susans, Russian sage, amsonia,
goldenrod, and all kinds of asters in all kinds of combinations. In the heat
of late summer your garden can be as beautiful as it is in the spring with a
few tough ornamental grasses to carry you through. When fall color starts to
show in the trees, your grasses will surprise you with shades of yellow, burgundy,
and gold as they turn dormant for winter.