If I plant ornamental grasses will they take over my garden and become invasive?
Answer: Some gardeners shy away from ornamental grasses for fear they’ll take over the garden or escape into nature. Some of the exotic grasses popularized in the 1980s and 1990s have proven to be invasive or potentially invasive in wild landscapes in certain parts of North America. The list includes Japanese blood grass (Imperata cylindrica), Chinese silvergrass (Miscanthus sinensis) and crimson fountain grass (Pennisetum setaceum).
It’s helpful to understand that all grasses grow by means of a creeping rhizome (an underground stem). New shoots arise at intervals along the rhizome as it pushes through the soil. If the rhizome grows very quickly and the shoots are spaced at long intervals along it, the grass forms an interwoven mat or turf (this type of growth is called rhizomatous). This is a desirable quality in a lawn grass but not so desirable in mixed plantings. A host of grasses produce very short rhizomes with shoots stacked up one atop the next. These clumping or bunching grasses expand very slowly and as such are much more useful in mixed garden plantings.