Miscanthus Giganteus Advice


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So I planted Miscanthus Giganteus grass along the road frontage on the West side of my property in 2015 to create a screen while my norway spruce grow to create a permanent screen. I haven't been doing a good job with weed control as the native grasses have really taken over. I guess I don't mind because they are about 5 or 6 feet tall with my second year MG planting.

My question is if I did better weed control would I get better growth? Also what herbicide do I use. I have heard 24D would work and not kill the MG grass. Here are a few pictures.





I am by far no expert so I am communicating what I have been told......as I just planted my own MG just earlier this fall. 2-4D will handle broadleaf weeds and not harm the MG. For fighting grasses I have seen and heard that you can spray virtually whatever you want as long as the MG is dormant. I also know of people using atrazine (controlled herbicide) or Simonize (uncontrolled) can help as well and not hurt the MG from what I am told. Talk to FISH here as I know he has experience with MG far greater than I, I think he has a thread as well where he may discuss what he does also.....see if this link helps.
I went through in August and sprayed the piss out of everything with 24d...totally soaking the MG and all surrounding vegetation. Results were dead vegetation and MG didn't skip a beat. From your picture I think 24d would knock back a lot of that stuff.

If you want to knock grasses back, I would get set to spray early as possible in the spring.....mid-late April when the grass is growing but the MG should be dormant still.

I believe it need 60 degree soil temps to get going.
As CAS mentioned. Early spring when the miscanthus is dormant but cool season grasses are growing, spray overtop of your miscanthus with glyphosate to kill any competing vegetation. An established miscanthus clump will kick butt if it has that kind of help. Come back with 2-4d when they are about a 2-3 foot tall if broaadleaves have started. Then stand back!
Simazine is easy to get and can be sprayed early spring with gly. But not real necessary. Helps the first year.
Thanks everyone really appreciate the information. I will tackle this in the spring and keep you posted .

Does anyone throw any fertilizer down or soil conditioner to help get better growth?

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I have not and some of my plantings are on gravelly soil. They have done well.
The www.mapleriverfarms.com website covers recommended weed control and use of 2-4d,other herbicides and fertilizer. Likely you have bought the rhizomes from them. They are the PREMIERE experts for sure. I copied the info below off of their site which addresses fertilizer and use of herbicides. Weed competition slows down all plants somewhat and when herbicides can be used it is the easiest most effective way to help get a plant established (that's my not a pro take on it).


Planting and Care Info

The individual rhizomes should be planted 3-4 inches deep, horizontally with nothing above ground. A well-tilled bed does help the roots establish quicker, but is not necessary. More importantly, adequate moisture and 60°+ ground temperature will promote growth. Do not worry so much about grass competition, but more so with broadleaf weeds that block sunshine - just during the first year of establishment. Second year growth will outpace everything.

It is not necessary at the end of year one to cut down the dead stalks. Neither is it necessary to cut down stalks every year going forward because the heaviest growth is always on the outside circumference of the cluster. Having said that, it does benefit growth to remove the stalks every year if possible.

Light fertilizer late summer/early fall the first year is acceptable, but not necessary, but the beginning of the second year growth and following years with help greatly. Anything you would be putting on your lawn would be fine. Next spring you can fertilize a little heavier as they are more established. We often go straight urea 40-00 because of the inexpensive volume of nitrogen the miscanthus just loves. We apply half a fistful on each cluster in the spring and that's it for the year.
The rhizomes are planted about 4" deep into a well prepared seed bed in the spring as soon as soil is workable. A little deeper if the soil moisture level is low. Europe has been working miscanthus for over ten years. They plant at one plant per square meter for establishment. Here in the U.S. we are planting at one rhizome per square yard - three foot plant spacing in rows three feet apart. That rate would require approximately 4,850 plants per acre. Row layout and density is up to the grower based upon a field planted to be lifted in two years (denser) or for establishment. Also, a field planted to match equipment already owned for cultivation could change row width and spacing. Good yields can be achieved on a wide range of soils but the key to high tonnage is moisture supply. A wide range of PH is tolerated but growth is best between 5.5 and 7.5 PH. Sandy or free draining soils only yield well if rainfall is adequate so should be avoided if possible.


This is a crop that will produce for 15-plus years so consider your site selection carefully. Thorough site preparation, particularly weed control is essential to ensure vigorous establishment. Also, water the crop (if possible) following planting and continue to irrigate the first year if necessary. Weeds can check growth the first two years of establishment. Glyphosate based herbicides can be used in the dormant period between harvest and initiation of spring growth. Miscanthus is in the grass family like corn. Common corn herbicides- Dual, Atrazine, 2D, 4D - for weed control have successfully been used.

Fertilizer demands are low due to the plant's efficient nutrient use and its ability to pull nutrient back down to the rhizomes at the end of each growing season. Almost every year, decomposition of the leaves, rhizome nutrient reserves, and atmosphere deposition will meet the crops nutrient requirements. After the first year, only small quantities of nutrients will be needed every two to four years to help maintain good yields.