How Do Your Grasses Grow?
This article is an excerpt from Grasses, by Nancy J. Ondra.
Ornamental grasses aren't what you'd call no-maintenance plants, but they're definitely on the low-maintenance end of the fuss-and-muss spectrum. They'll thrive with the same good care you give your other garden plants, and they're normally not much bothered by pests or diseases.
Early spring is the ideal time to get warm-season grasses in the ground, so they can put down some roots and be ready to shoot upward as the temperatures start to rise. You can plant cool season grasses any time, although early spring usually works best for them, too.
Don't go to a lot of bother with soil preparation - definitely hold off on the rich manures and fertilizers, as ornamental grasses don't enjoy an overly rich soil - but do loosen the soil as you would for any other plant. Be sure to rid the planting area of any weeds before you plant, particularly if you're plagued by
pesky perennial grasses, such as quackgrass (Agropyron repens). Trying to weed out unwanted grasses from your carefully chosen cultivars can be the gardener's ultimate nightmare.
Grasses should be spaced about as far apart as the mature plants will be tall. For smaller grasses, that equates to 12 to 30 inches apart; for taller ones, allow 4 to 5 feet between clumps. They will look a little sparse at first - especially if you're starting with small grass plants - but they will expand over time. If you want a fuller look faster, you could space the plants more closely, but then you'd need to dig up and divide the crowded clumps several years sooner than you would otherwise.
Plant grasses the way you would any other perennial. If you are planting a grass that's been growing in a container, water it well before removing it from the pot. Dig a planting hole that's large enough to hold the roots or root ball comfortably. It should be just deep enough that the crown of the grass (where the leaves and stems come out of the roots) will be even with the soil surface, or slightly above. Slide the potted grasses out of their container and set them in the center of the hole. Or, if you're working with bare-root grasses, first make a mound of soil in the center of the hole, then set the crown on top and spread out the
roots over the mound as evenly as you can.
Next, add more soil around the roots until the hole is about half full, then water generously. Let that water soak in for a few minutes, then finish filling the hole with soil, and water again. After planting, add an inch or two of mulch around the plant, being careful not to pile it right against the crown. It's important to allow room for air circulation, as excess moisture near the crown can promote rot.
Feeding and Watering
Most grasses require minimal maintenance. You shouldn't fertilize heavily, because an excess of nitrogen can lead to lush, soft growth that tends to flop. Mulching with 1 to 2 inches of compost each year will help keep the soil and your plants in good shape. Water grasses regularly during their first year to help get a good root system established. Even grasses that are normally touted as drought-tolerant require a season or two to become fully established. If you've chosen grasses that are adapted to your climate, you shouldn't have to do much supplemental watering after the first year. If you decide to irrigate your grasses or if they're growing with other plants you'll be watering, use soaker hoses to direct water to the roots while keeping the leaves dry, thereby minimizing disease problems.
Be aware that watering can have a dramatic effect on the height and the sturdiness of certain grasses. Deer grass (Muhlenbergia rigens), for instance, grows about 2 feet tall in dry conditions, but when it gets plenty of moisture that height can double. Keeping the soil a little on the dry side can help keep often floppy grasses, like some miscanthus (Miscanthus spp.), from getting too lush and sprawling.
The principal task with grasses is cutting them back to remove old foliage. Many gardeners like to cut down and clean up their gardens in fall, and that's fine for grasses that usually don't last well into winter, including giant reed (Arundo donax), hair grass (Deschampsia spp.), Lyme grass (Leymus arenarius), blood grass (Imperata cylindrica var. koenigii 'Red Baron'), and ravenna grass (Saccharum ravennae). Cutting back all dried grasses makes good sense - and even is required by law in some locales - if you live where wildfires are a frequent problem.
Having said that, there are some compelling reasons to let warm-season grasses stand for the winter, if you can. For instance, leaving the foliage intact can help protect the plant's crown from cold and moisture, minimizing the chance of winter rot. In addition, you'll be able to enjoy the beauty of the seed heads and the foliage, and wild birds will appreciate the seeds and shelter. By the time the top growth starts to lose its appeal - in late winter or early spring - you can cut it down to 4 to 6 inches above the ground to let the fresh new growth emerge.
Cool-season grasses go dormant during hot weather, so they'll need a little atten- tion in early to midsummer to keep their good looks. For some, such as blue oat grass (Helictotrichon sempervirens), grooming is simply a matter of raking or plucking out the dead foliage. On others, you may want to cut back the top growth by about half to get a flush of fresh new foliage for fall. This works well with Lyme grass, hair grasses, ribbon grass (Phalaris arundinacea 'Picta'), and perennial quaking grass (Briza media).
For cutting back a small grass, handheld pruning or grass shears work just fine. Larger grasses need more powerful tools, such as electric hedge shears or even a power trimmer with a blade attachment. The leaves of some grasses have surprisingly sharp edges, so wear gloves, eye protection, long sleeves, and long pants when cutting down your plants. Before cutting, make sure there are no forgotten metal stakes in the ground that might be hidden by the foliage. Tying up the top growth with twine before cutting can make cleanup a
snap: you'll have one neatly tied bundle to pick up, instead of having to rake up dozens of stalks that are scattered throughout the garden.
The Choice Is Yours
Deadheading grasses can be a matter of aesthetics or a matter of sanity. In the former case, you might choose to snip off the flowers in favor of the prettier foliage or just leave them alone if you don't have time. With some grasses, though, sparing the clippers can spoil your garden - or at the very least give you more weeding to do. Of course, removing the flowers before they set seed will eliminate weeks or months of enjoyment. But, on the other hand, if you remove the unwanted seedlings, it could save you years of laborious weeding. Prime candidates for deadheading include the following:
Bottlebrush grass (Hystrix patula)
Broomsedges (Andropogon spp.)
Fountain grasses (Pennisetum spp.)
Indian grass (Sorghastrum nutans)
Japanese silver grass (Miscanthus sinensis)
Korean feather reed grass (Calamagrostis brachytricha)
Melic grasses (Melica spp.)
Perennial quaking grass (Briza media)
Switch grass (Panicum virgatum)
Tufted hair grass (Deschampsia cespitosa)
Wild oats (Chasmanthium latifolium)