Ornamental grasses lend beauty to the garden with their foliage and seed plumes. They also are well suited for container culture. Matching the growing requirements of a grass with the appropriately sized container, using the correct growing media/soil and providing good drainage is the formula for success. By anticipating the growth rate of the grass and repotting the plant when needed will allow for many years of enjoyment in the garden.
Purchase a container-grown ornamental grass that is healthy looking, robust and attractive from a plant nursery. Ideally, the plant should not have roots coming out of the draining holes of its pot, as it is a sign of a root-bound plant that may readily wilt.
Note the size of the container of the ornamental grass just purchased. Also read the plant label for information on this grass's mature size. Ask a nursery professional for the mature size of the plant if no plant label is available.
Prepare a container that is no less than twice as wide as the purchased grass's current pot. Make sure this container is sturdy and has at least one drainage hole in the bottom. To prevent winds from toppling the plant in this container, make sure it has some weight to it, especially if the plant label read in Step 2 mentions that this grass gets tall.
Purchase a soilless potting mix to fill the container. Potting mixes that are bagged (with or without fertiliser incorporated) should be made from peat and/or compost.
Test the potting mix before planting to make sure it is moist to the touch and there is no dust. Peat-based potting mix that is dry should be wetted first; a bag of mix that is saturated should be opened and allowed to dry to a damp condition before it is used.
Pull the ornamental grass out of its nursery pot, noting its size.
Roughen the rootball with your fingers or garden trowel, making small cuts or tears in about 3 to 5 places. This ensures that new roots will grow out from the rootball rather than continue to encircle and entangle in the same rootball shape.
Note the size of the rootball and begin filling the decorative container with potting mix. You want to match the top of the grass's rootball with a line about 1 inch below the top of the container. Add or take away soil as needed until the rootball sits at the correct height in the new container.
Tamp or push down the potting mix so that the grass sits snugly and evenly in the decorative container. The top of the rootball should be at the same height as the added potting mix, at 1 inch below the container's rim.
Water the newly planted grass in the container, adding a little water at a time. The container's rim should catch the water like a reservoir until it soaks into the soil. A second or third watering may be needed as the container top fills and soaks away; once water drains out of the container's bottom drainage hole, watering can stop.
Check to see if the rootball of the grass and the soil level in the container are still even. Add a small amount of potting mix if the rootball is higher than the soil; take away if the rootball is lower. Remember to keep a rim of 1 inch between the soil line and the top of the decorative container.
Expect to water the newly planted grass every day or two. The soil will drain more quickly and warm faster in a container and should be checked daily. As the grass quickly grows, watering may be required even more frequently. Putting a saucer under the container can lessen the amount of watering needed.
Be mindful that once the ornamental grass establishes in the container, it will grow quickly both in foliage and its thirsty, fibrous roots. Use the right-sized container for the ornamental grass: don't put a 5-foot-tall growing grass in a container that is 1 foot tall and wide. Even if you start with a larger container, it is possible that in 3 or 4 months the grass roots will have completely filled up the container. Expect to repot to keep the grass vigorous the remainder of the growing season, or for next year after the winter dormancy.
Never use garden soil or topsoil in containers. With the frequent watering and drying of the soil in containers, regular garden soil and topsoil will compact and turn hard after only a couple of days.