As grasses become garden staples, they are also finding their way into more and more containers. Growing ornamental grasses in containers is a great way to feature grasses without the worry of them spreading or taking over the garden. Container grown ornamental grasses are also much easier to divide.
The downside is that when growing grasses in containers, their hardiness is raised by about 2 zones.
An ornamental grass hardy to Zone 5, when planted in the ground, will probably only survive to Zone 7 in a pot. The actual hardiness of ornamental grasses grown in containers depends upon the location and material of the container, the very variable weather fluctuations of the winter months, and how well you winterize them. However, you can always treat ornamental grasses in containers as annuals.
Caring for ornamental grasses in containers is basically the same as any other outdoor potted plant. They will need regular water, but most are not as thirsty as flowering plants. Your grasses will also need feeding with a high nitrogen fertilizer a couple of times during the summer. Other than that, the major maintenance will be dividing them. Grasses will quickly outgrow their containers and may crack through them, if not removed, divided and repotted. But as I mentioned above, it's a lot easier to slip a grass out of a container than it is to dig one up.
You will also need to cut your grasses back each spring.
Here are my top ten picks for ornamental grasses grown in containers.
- Blue Lyme Grass (Leymus arenarius) Leymus can spread too quickly in a garden bed. Planted in a container you still get the imposing sword-shaped leaves that bend as they grow tall and the spiky flower heads. Zones 4 - 9*
- Blue Oat Grass (Helichtrichon sempervivens) Containers of Helichtrichon bring a cooling blue-gray to the garden as well as a gentle rustling sound and reach-out-and-touch texture. Zones 4 - 9*
- Red/Purple Fountain Grass (Pennisetum setaceum 'Rubrum') Fountain grass is a natural for containers, filling the pot with its arching habit. The rich, burgundy color of 'Rubrum' has made it a favorite even where it's an annual. Zones 9 - 10*. Others to try include: Pennisetum 'Burgundy Giant' and Pennisetum orientale (Oriental fountain grass, Zones 7 - 9*)
- Japanese Forest Grass (Hakonechloa macra 'Aureola'). It seems everyone wants Hakone grass once they see it. If you don't have the moist, partially shaded conditions it thrives in, try growing it in a pot. Zones 5 - 9*
- Bamboo Muhly (Muhlenbergia dumosa) This southwest native, got the name 'Bamboo Muhly' because of it's notched stems and feathery, bamboo-like foliage. It thrives in sun and heat and can take a bit of neglect in a container. Zones 8 - 11*
- Feather Reed Grass (Calamagrostis x acutiflora 'Karl Foerster'). Karl has wonderful, tall flower plumes that create an eye catching focal point when grown in a container. Although feather reed grass needs a bit of protection from the hot sun, it can survive winters in containers down to zone 6. Zones 5 - 9*
- Leather Leaf Sedge (Carex buchananii). Sedges are not real grasses but I mention this one here because they don't get the notice they deserve. They can get lost in a crowded garden, but grown in containers, their bronze tinged leaves gleam in the sun while the narrow blades pick up the slightest breeze. Zones 6 - 9*
- Japanese Silver Grass (Miscanthus sinensis 'Morning Light'). One of the most popularly grown grasses does just as well in containers. The airy growth habit has a softening effect and the white on the leaf margins brightens. Other good choices include: Miscanthus sinensis 'Variegatus', Miscanthus sinensis. 'Autumn Morning' and Miscanthus sinensis.condensatus 'Cosmopolitan'. Zones 4 - 9*
- Japanese Sweet Flag (Acorus gramineus 'Ogon'). Sometimes a container calls for something short. At a foot or less, Sweet Flag adds beautiful gold color and the familiar sweet scent. Needs water and some shade when grown in a container. Zones 10 - 11*
- New Zealand Flax (Phormium tenax and hybrids). Phormiums are frequently used and seldom recognized. For spiky, sword-like form and a variety of colors, including greens, reds, copper and yellow, they are perhaps the most versatile container grass-like plant to design with. Zones 9 - 10*
* Zones listed here are for ground grown plants.