While Miscanthus Giganteus is adaptable to many types of soils, it will do best in moist, fertile soils.
If you have very infertile or sandy soils you may want to amend areas where you are planting this. After a year or two of establishing it should adjust to your areas normal conditions, but amending right where you are planting will help it the first year as it establishes. Amend sandy soils with compost, peat, or manure or a combination of any of these.
When planting in moisture saturated soils of late fall and early spring, especially while it’s cold out, roots must have superior drainage. Roots will not have adequate feeder root to take up excess moisture and will not grow the feeder root until temps warm. Eliminate rot and mold issues by adding sand for a few inches around the roots, a good shovel full of sand per hole. The only losses of plants both to us and to customers that we have seen have come from too much or too little moisture when planting. You as the purchaser are responsible to amend your planting area as needed to ensure success.
Your site should receive 6 hours of sunlight for good growth. While miscanthus likes lots of moisture, it also has woody root system, which can rot in overly wet conditions. Swampy areas are not suitable to this plant. If your area tends to have standing water parts of the year, you may want to elevate your plantings a bit by adding soil.
Eliminating competing vegetation is highly recommended to help miscanthus establish well. If you are able to spray the area with an herbicide before planting this is best. If you have not been able to apply an herbicide to that planting area, you can mulch around the areas where you plant, which will mark your planting spots. Then in spring as competing vegetation greens up, you can spray an herbicide around the the planting area. Miscanthus will not grow until temperatures are in the mid 60’s regularly, which is usually mid May in Michigan. There is often time to spray the competition before miscanthus is actively growing, or at least if it is growing, you’ve marked where it’s at and you will be able to see it and avoid spraying it. Pre-emergent products (such as Simazine) can keep vegetation from growing from seeds. Products like 2-4D will kill off broadleaf weeds but not damage miscanthus and can be used during the growing season.
Another method used for weed control is to place a thin, inexpensive grade of landscape fabric around the plants. You can do this by laying the fabric out, pinning it down with pieces of wire bent to make small stakes, and then cutting holes in the fabric when you plant. Or you can place the fabric around areas you have already planted, being sure not to cover the plants themselves. This method helps keep weedy plants from growing while the miscanthus establishes and also acts a mulch, keeping moisture in. The grass is vigorous enough that it will grow right through the ground cover in years to come and a cheap grade of landscape fabric should break down in a few years time. So for a small investment you will have helped your plants greatly, eliminated the need for sprays and herbicides to a great degree, and also marked the areas where your grass is planted.
To plant, simply dig a hole roughly 8-10″ deep, place your division in the hole at a depth so that 2-4″ of soil will be able to cover it. If you can tell where the rhizomes are pointing up, plant them in this position. If you can’t tell what is up and what is down, it’s no problem. There are growth buds all over the rhizomes and they will find their way to the surface. The most important thing when planting is just to be sure the root is covered well with soil and at a depth not too close to the soil surface so that it will not dry out.
If you are planting single rhizomes the hole will not have to be a deep as for divisions. You may lay the rhizomes flat and cover with 2-4” of soil.
Mulching your plantings will help keep competing vegetation at bay and will help keep moisture in. While miscanthus will store up the nutrients it produces, much like a bulb, we have found that fertilizing in the first growing season does help this plant. Using all purpose types of fertilizer or 12-12-12 products works well.
Caring for Miscanthus Giganteus does not have to require lots of work. However you may divide off of your plants after each growing season if you wish to increase your rootstock or to keep your plants within boundaries. Be aware that leaving your plants without dividing for several years will produce large clumps that will become heavy and hard to lift. You cannot simply shovel a portion of the root out, the entire clump needs to be dug, so keep this is mind and divide every few years if you wish, or leave the clumps to stand as is and expand. You do not need to cut your top growth off unless you wish. It will grow up through the debris left from the previous year. However you may wish to cut your old growth off to keep things neat and tidy. You may also burn the top growth, which seems to invigorate the growth of the plant.