Big Bluestem
Big Bluestem (Andropogon gerardii) once covered much of the Midwest and was one of the main food sources for the prairie buffalo herds. It is currently enjoying a resurgence in several uses; the first is with using this grass as a hay source because of its high nutrient level, the second is in prairie restoration projects, and the third is in ornamental gardens because of its height.
This article won’t talk about the first two uses as these tend to be rather technical subjects and are well covered by university and conservation writing. This article will focus on the ornamental use of the plant in the perennial or grass garden.
The first thing to understand is that this plant does not like competition. It does not establish quickly (unlike other grass plants) and will usually take at least two years to establish and begin to create a presence. So if you’re trying to establish a stand of it in your home garden or home project, you do have to keep it weed free without competition or shading until it is well established.
Starting Seed
Seed is started by sowing on a firmly soil bed. The easiest way to do this is to cultivate as normal and then whack down the soil with the back of a shovel to firm it up and create a smooth seedbed.
The seed is sown (spacing approximately one-half inch between seeds) and then barely covered with soil or compost. The purpose of covering the seed is to stop birds from eating it and to preserve moisture around it to aid germination. Keep the area damp until the seed germinates. It is an easy germinator with warm soils in mid-spring about the time you’re planting the cauliflower and broccoli. (more tender than pansies but tougher than petunias) Remember to keep it well weeded.
Big bluestem is called a warm-season bunch grass. Unlike other grass plants that can not tolerate the high heat of summer days and go dormant, this one thrives on the heat and you’ll see the major growth spurt between the middle to end of June to middle of August as the heat increases. It is a bunch grass because it grows in little clumps rather than sending out rhizomes and forming a mat.
Big bluestem flowers in late summer and at maturity will easily top 8 feet in height. You won’t write home about the purplish-bronze flowers on this plant, they are three branched and resemble a turkey foot (giving rise to another common name of ‘turkey foot’ or ‘turkey claw’ grass). The foliage does turn an attractive red-bronze in the fall and this is the reason you’ll want it for the perennial garden.
Germinating Seed
Some gardeners have reported difficulty in getting the seed to germinate. This grass does have a seed-dormancy issue sometimes depending on how it has been stored.
If you’re having trouble with germination, sow earlier in the season to give the seed a cold period or store it in the crisper of the refrigerator for at least 90 days (put it in there in the fall and plant in the spring) to give it a cold dormancy. Freezing the seed will not increase germination and while this is often recommended, dry freezing will likely kill seed rather than help it. Cool temperatures in the refrigerator will do the same job with no damage.
Do not feed the young grass anything but compost. Nitrogen will feed the weeds and slow down early growth of big bluestem. Remember that in its native area, it never saw fertilizer other than the odd buffalo pattie. In hay fields, there is nitrogen applied after the crop is established and the plant does well with it at this time. So once your plants are established in the garden, do not worry if you feed them a little.
It is a very tough plant with deep roots once established and while all the other perennials are struggling in the heat and drought, big bluestem will thrive.
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