Hello, which ornamental grasses have reseeded for you in Colorado? Did you consider any of them downright invasive?
Much as I love them, my blue oats (Heliotrochon sempervirons) are starting to get that way, but only the ones that are in more fertile soil and some shade and more (as opposed to no!) watering. The ones in the picture are in sand and are virtually rainfall-only.
I lied. I just found a few strands of blue oat in the middle of my lavender on my dry sandy slope.
No kidding! My neighbor planted blue oat grass about three years ago, and it has been so well-behaved. But then, he has clay soil.
Thanks for letting me know.
Many of the "native" grasses that have become popular in recent years will reseed, like sideoats grama, glue grama, little bluestem, Indian grass, etc. But then it's logical that they would, because those are the grasses that grow--and spread--in the tall and short grass grasslands like the Oglala National Grasslands in the Panhandle of Nebraska.
In spring and early summer the grasslands are a beautiful sight to behold!
If you stay away from the "grassland natives," and look for the more "ornamental" grasses, most of them will behave pretty well for you. And many of the newer hybrids are sterile, so they pose no problems at all. An example is Fescue! The green fescues used in lawns will reseed all over the place, but the hybrids of the ornamental blue fescues, like 'Elijah's Blue', a favorite of mine, is sterile.
In many cases the straight species are the ones that can be a problem, but if you find hybrids of the genus you're looking for, you won't have a problem. For instance, there is a straight species Miscanthus growing on the Atlantic coast that is a noxious weed and is apparently causing a lot of problems, but the Miscanthus hybrids (which I LOVE) are mostly sterile or virtually sterile. So you can't rule out a whole genus because there can be "bad" ones and "good" ones within any genus, and you can't even rule out a genus/species, because that straight genus/species might reseed, but a hybrid of the same genus/species would be fine! Basically, the best general advice is to look for hybrid varieties, and then maybe google them to see what comes up--but beware the Naysayers when you google them, because there are people out there who throw the baby out with the bathwater--they rage against ALL Miscanthuses because they're just too lazy to figure out which ones are ok!
I'll copy my list of OGs that "may self seed" here, but it's copied from a Word document, so I'm not sure how well it's going to "translate" when it's copied here! You'll notice that there are no hybrids on this list! I'm sure there are things that are not on this list, but at least it's a place to start!
Ornamental Grasses That May Self Seed
Alopecurus -- Meadow Foxtail
Bouteloua curtipendula -- Sideoats Grama
Bouteloua gracilis -- Blue Grama Grass, Mosquito Grass
Briza media -- Quaking Grass
Chasmanthium latifolium -- Northern Sea Oats
Deschampsia caespitosa -- Tufted Hair Grass
Schizachyrium scoparium (a/k/a Andropogon scoparius) -- Little Bluestem
Sorghastrum nutans -- Indian Grass
Stipa tenuissima -- Ponytail Grass
Hope this helps some at least!
Thanks for your thoughtful reply, Skybird!
My blue oats won't reseed, but I sure wish they would! My pennisetum doesn't either, nor does my miscanthus ('Morning Light' cultivar). I don't grow stipa but have seen tiny tufts of self-seeded ones around my work building. Chasmanthium is my absolute favorite ornamental grass ever, I get maybe 1 or 2 babies a year from it (but they usually don't make it through the summer, not sure why...sob....).
I didn't think that Northern Sea Oats were hardy enough to survive here. But then, I'm beginning to think that Colo Spgs and the Denver area are very different. For that matter, we have a tremendous number of microclimates just here in the Springs!
I've heard that northern sea oats can get downright invasive in Denver, but I don't know that from personal experience.