By late summer, it begins to bear panicles of its namesake oat-like, green flower heads, which are its chief ornamental feature. Not only are these flower heads visually appealing with their jagged edges, but they also flutter in the wind, creating a rustling sound that adds interest to the landscape. But while the plant does afford summer interest, northern sea oats comes into its own in fall. This is when the flower heads begin to ripen into seed heads and change to a bronze color. As fall progresses, the leaf blades change to a golden color to complement the seed heads. Although the foliage color eventually fades to a tan color, the plant continues to offer landscape interest in winter. Locate northern sea oats in a spot where it can be accompanied by other plants that enjoy the same growing conditions and that can complement it. For example, northern sea oats can provide a contrast in texture with compatible plants that have wider leaves, such as Rodgers flower (Rodgersia aesculifolia). A row of northern sea oats plants also makes for a great backdrop to a bed of shorter plants.
Light
Give northern sea oats full sun to partial sun. While it will survive if grown in partial shade, it will not thrive to the same degree: Flowering will be reduced, and its fall color will not be as strong. This is an important consideration since northern sea oats is grown mainly for its flower heads and for its fall color. However, the more sun it receives, the more water you should give it; so be prepared to provide it with more care (irrigation) if you are growing it in an area with full sun. If low-maintenance landscaping is more important to you than optimal performance, grow it in partial sun so that you can cut back on watering. At the southerly end of its range, the summers are so hot that it is best to grow northern sea oats in partial sun or even in partial shade.
Soil
Northern sea oats likes well-drained, fertile ground. A loamy soil fortified with compost is ideal.
Water
Northern sea oats has only moderate moisture needs if grown in partial sun or partial shade, but it does not like for its soil to dry out completely. Aim for a consistently moist soil, especially during the heat of summer.
Temperature and Humidity
Northern sea oats performs best in climates with moderate summer heat and humidity. It does not perform well in the Deep South, which is why the most southerly USDA zone it is listed for is zone 9.
Fertilizer
Northern sea oats needs a fertile soil to perform optimally, so feed it annually with compost or manure tea.
Types of Northern Sea Oats
Chasmanthium latifolium is one of five species of Chasmanthium, but the other four are not as commonly grown. The other four species are:
Chasmanthium nitidum (shiny wood-oats)Chasmanthium ornithorhynchum (bird-bill wood-oats)Chasmanthium sessiliflorum (long-leaf wood-oats)Chasmanthium laxum (slender wood-oats)
But some nurseries and online catalogs do carry a variegated leaf cultivar of Chasmanthium latifolium known as ‘River Mist’. As with many variegated plant cultivars, it likes a little more shade than the species plant.
Propagating
The best (easiest) way to propagate northern sea oats is through division. Divide and transplant it any time between mid-spring and early summer. Do not let its soil dry out completely during this operation.
How to Grow Northern Sea Oats From Seed
Northern sea oats is also easy to start from seed. No special steps are required to get its seed to germinate. You can either collect the seed in fall or buy it; the seed is readily available for sale online.
Common Pests and Plant Diseases
Northern sea oats is bothered by few pests or diseases. Most importantly, the deer leave it alone; because of their size (and thus their ability to eat so much), deer, where they are present, are typically the landscaper’s worst nightmare.
How to Get Northern Sea Oats to Bloom
Provided that they have been planted in full sun, northern sea oats will readily start blooming in the late summer each year, with little extra help from you. The flower head, which imperceptibly morphs into a seed head in fall, measures about 1 inch long and wide; it is razor-thin. For optimal flowering, simply keep the soil evenly moist and give the plant an annual feeding. Since the flower head is the main draw of the plant, do not deadhead.
