Gardening Unplugged - Ornamental Grasses

Gardening Unplugged - Ornamental Grasses

with Tony Avent

By Published November 2022

In this episode of Gardening Unplugged, Tony Avent gives guests a walking tour of the many examples of ornamental grasses available for gardeners today. Learn what makes a plant invasive and why well-behaved ornamental grasses have a place in every garden.

Ornamental Grass species that Tony mentions in this video:

Arundo donax ‘Peppermint Stick’

Bambusa multiplex ‘Green Giant’

Carex digitalis

Carex gentilis

Carex montana

Hakonechloa ‘Japanese Forest Grass’

Juncus inflexus

Miscanthus giganteus

Miscanthus sinensis 'Zebrinus'

Miscanthus transmorrisonensis

Muhlenberg capillaris

Muhlenbergia dumosa

Muhlenbergia emersleyi

Muhlenbergia sericea

Muhlenbergia lindheimeri

Muhlenbergia sericea 'White Cloud'

Pennisetum alopecuroides 'Hush Puppy'

Pennisetum ‘Oceanside’

Panicum virgatum

Saccharum arundinaceum

Sorghastrum nutans

Sorghastrum nutans 'Slim Pickens'

Schizachyrium scoparium

Sporobolus airoides

Sporobolus wrightii



Video Transcription

Are you ready? Okay, all right everybody that wants to join us for our ornamental grass walk we'll get started. I'd like to welcome everybody here to Juniper Level Botanic Garden and Plant Delights Nursery, and for those that haven't been through one of these before we sort of take a 15-minute walk and we're just going to look at today, ornamental grasses. So, this is going to be a little bit of an excursion because we got things scattered all around, so please excuse that. So, let's begin right over here.

A Brief History of Ornamental Grasses

The world of ornamental grasses is really a fairly big world and we're going to include today things that look like grasses that are closely related to grasses and those would be the genus Carex and those are generally going to be a much smaller grass. So, I'll begin here with, and there's several genera of grasses and we're probably going to be 12 to 15 genera that really comprise what we know of as grasses. And the reason we're really interested in grasses is it was a trend that started back in the early 80s. It was and really was brought to the US by the Europeans, the Germans in particular, a landscape architect named Wolfgang Oehme. Back when the in the early to mid-80s he brought what was called the naturalistic style of German gardening to America and began using American plants in ways that people had not used before. The Germans are very high on American plants, so they really appreciated some of the natives we had. And what was really interesting, they added a whole another element, especially to the fall garden, but they added a textural element that we really did not have in the gardens. Now the grasses are not pollinator plants, they're not a plant that's going to attract pollinators, because they are wind-blown pollinated just like the oaks in spring, the pines, etc. But they do add a really neat thing and they also host a number of plants that may not be pollinators on the grass, but they require the grass or the sedge for part of their lifestyle.

So we'll begin with a genus that you probably know but you may not know this species. This is the genus Muhlenbergia. It's a fairly commonly grown plant now, was not 20 years ago and we'll see that a little later. People know it of the pink flowered one known as Muhlenberg capillaris. This is one from northern Mexico, so it is a North American Native. This is one called dumosa. This is originally brought in by a Yucca Do Nursery down in Texas and none of it was hardy here. So, our director of horticulture Patrick McMillan went back into the wild populations, went into a colder area, and brought back a colder form that we are currently trying. And hopefully, this will survive when we have some really harsh winters again. But this one is deciduous; it does go down to the ground in the wintertime but comes back and sort of has a look like bamboos which I really like.

Now one that is not flowering yet is this blue foliage grass over here, this is a sorghastrum. So, this is, people know [it as] Indian grass, which is fairly commonly grown in the ornamental grass world. But most of what was grown is a form that really does much better up north, it really does not do well here. This is Sorghastrum nutans. This is one of Patrick's collections from South Carolina, so it has this beautiful upright form, and this is from Pickens County South Carolina. And it's a very nice upright form, full flower in October, so we've introduced this one under the name of 'Slim Pickens.'

Now, right here in front of us is another great group of native grasses, these are the schizachyrium, or the blue stems. This, if you've come and seen this in spring summer, it's beautiful powder blue and then in the fall it gets this beautiful russet color. Some of the earlier forms really sort of fell over, we like these that are more upright. Anytime they get into full bloom they're going to be sort of arching, but these don't do the splaying that we found in some of the very early cultivars. And there's some really amazing Schizachyriums. The species on almost all of these is scoparium.

What is an Invasive Plant?

I'm not going to drag you all the way down, but if you take a look straight to the end of the parking lot, this is one of my favorite grasses. And this is a big ornamental grass. This is the genus Arundo. So, this is Arundo donax and this is a variegated form called 'Peppermint Stick'. There was an old, variegated form that was grown for years, but by mid-June it turned green, so it wasn't really as exciting. This one was found in England. It's an amazing grass. It's a very thick stemmed grass. It flowers now, it's just coming into bloom, so when we finish take a walk down there, it's really quite amazing. This plant is more known for being the source of reeds for wood instruments. So, if you've ever played a wood instrument; a clarinet, etc.., etc., that's where the reeds come from! They're still made out of that plant. Now about four years ago we had a movement by the Department of Agriculture to look at banning that, because they had been asked by the native plant people to ban it for being invasive. And so, we got a call from them and said: "What do you, what do you know about this plant?" And I said: "Well, we've only grown it for 35 years." I said it doesn't meet any criteria for being invasive. Number one, to be invasive a plant has to seed. All cultivars of this are sterile, so it cannot seed. Number two, it does not run. So, it has absolutely no way. So, what had happened, there was a hurricane down on the coast and it had blown parts of clump into several areas and people, instead of actually doing scientific research, freaked out, said "well it shouldn't be here, so it must be an invasive!" So, there's a lot of bad information out there. So, it is absolutely a very well behaved, as long as you've got a big enough area for that.

Right beside it, another muhlenbergia. This is one that we… you don't see this very often in the trade, it's a little more wispy and not quite as flashy as the others. This is Muhlenbergia emersleyi and this comes from out in Arizona deserts. Now we mentioned carex and I'll show you a few as we walk by. These are carex, this is what most carex look like. There's a lot of different carex we have over a hundred different carex through the garden. They're native all over the world. This is a southeast native, this is Carex nigra ‘Montana’. This is Carex digitalis. They're all variations on a theme. Carex are real... some are sun plants, some are shade plants, some are wet plants, some are dry, but they really add a wonderful texture. Where many plants in our woodland gardens are bold, the carex really give us a very different feel, and they're an incredible host for many, many great wonderful insects.

Another plant that has really got a lot of bad press is the genus Miscanthus. Again, appearing on a lot of invasive species lists by people who don't know what invasive species are. Miscanthus... To be invasive, it is a very specific definition. A plant must invade a functioning natural ecosystem displacing natives once population equilibrium has been reached, causing economic harm. That is the definition of invasive. You can't just make up your own. Okay, what happened with miscanthus is, they built interstate 40. And any miscanthus planted near there got moved by cars all the way up from one end of the state to the other. So now if you go to Asheville, every roadside on Interstate 40, every highway shoulder, is covered in this. But it does not move outside the highway shoulders, okay. That is not a functioning natural ecosystem, that is a man-made ruderal area. So, it is growing where no native plants would dare to grow. It does not move into the natural areas. That said, as a gardener I don't want a plant that's going to reseed all over my gardens. So, there are good miscanthus, there are bad miscanthus. So, through the years we've trialed probably 60-70 cultivars. Anything that we grow does not seed. [We're] Not interested in having a plant that seeds around. So, you've got to be very careful when you hear fundamentalists, who don't want to let their views get tainted by realities or real science, start spouting off - "well this is this and this is this" and so many people just aren't trained to go back and look at the actual data. So, there are bad miscanthus, there are good miscanthus. This is one of the old zebrinus types, it's one of the few plants that actually has horizontal variegated banding. Most plants have vertical banding, so this is a really neat, neat group of plants and certainly does still have a place in gardens.

Bamboos are Ornamental Grasses Too

Now in the grass family is another plant you see down here on the corner by the greenhouses. That is bamboo. Bamboos are ornamental grasses. Okay. And like the miscanthus, there are good bamboos, there are bad bamboos. No bamboo is invasive using the official term, because to be invasive a plant must seed, to seed a plant must flower. Bamboo flowers once every 100 years. That's it! That's the only time a bamboo will flower. So, bamboos are not invasive. Now within bamboos you have what we call pachymorphs and leptomorphs. Pachymorph means packed rhizomes, it's a clumper. Leptomorphs are leaping rhizomes, those are the runners, okay. As a gardener, I will never let a running bamboo in my garden under any circumstances, they are a disaster! Not because they cause ecologic harm, but they can ruin your garden. They will take over everything. This is a clumper, this is the genus Bambusa, b-a-m-b-u-s-a, Bambusa multiplex. This is one called 'Green Giant.' I love the look of bamboo, as long as it's not going to run and take over in my garden. I think they're absolutely fabulous plants. Within the clumpers you have those that love heat and hate cold, those that love cold and hate heat. So, we can, we're right on the borderline, we can grow both. This is a heat lover. If it drops below 10 degrees that goes to the ground and has to start over again, which it does fine. And then we have smaller ones, which I'm trying to see if we can... we may be able to see as we walk.

Just behind the palm there, you will see a bamboo. It's much shorter, about six to eight feet. That is one of the cold lovers that hates heat, and those belong generally in the genus Fargesia. So, you can see as we walk along here, and we looked earlier at the carex, see how we've used them here in the seat. That's the fine texture you'll see them here. And there are really neat carex from all over the world, as I mentioned. So, this would be a US native, the brown one there is an Australian native and that's the way it's supposed to look. It's supposed to always have brown foliage. Things in Australia and New Zealand are really weird if you've had the chance to go. The plants just don't look normal. So, there's a wide variety in the genus Carex. All right...

A genus of grass that you don't see in a lot of the books is in bloom up here, we've got it planted all amongst the palm. That is the genus Setaria. Setaria is a fascinating fall bloomer, it seeds a little much, you do have to be wary about that, but I love the textures, there's really nothing quite like it, because it'll top out at six to seven foot in height.

Now earlier we looked at the genus Schizachyrium. A very closely allied genus are the Andropogons, and these have, these are pretty much finished their season they're starting to go dormant now. But this is a beautiful andropogon called 'Blackhawks'. If you are here anytime during the summer, the foliage is jet black. It's really a neat plant both texturally and color wise, that you don't see very often. Now over here on this side is another fairly common genus that we haven't looked at yet. This is the genus Pennisetum. This is Pennisetum alopecuroides. It's an Asian native grass, one of the most popular genus of all the grass. Now in my world they're good Pennisetums and bad ones, they're the ones that seed all over the place, which I don't want, and the ones that don't seed at all. This is one of the sterile ones, this is one called 'Hush Puppy'. So, if you're getting a Pennisetum, you want one that does not seed, because the seedy ones you'll get like three or four hundred seedlings a year. And as a gardener that's not what I want.

Now up against the fence is one of the best genus of ornamental grasses, this is the genus Panicum. It is a genus of natives. This is Panicum virgatum, likes full sun. Now what's happening here, I've got these planted where they're starting to get too much shade, so they're starting to fall apart. Panicums normally are wonderful, and you'll see a lot more in the next section, and they range from leaf color, to green, to almost blue. They range in height from two and a half feet up to seven feet. So, a really wide range of native grasses, I think they're really incredible. Now I mentioned we talked a little about plants that aren't grasses, in addition to carex, and this gives the very much effect of a grass. This is juncus. This is Juncus inflexus, a wonderful... and this is a rush. So yeah, yeah grasses, rushes, and sedges all comprise what we know of as ornamental grasses. Juncus generally like it very wet, so we were testing these on the outside to see how they would do dry, and they've actually done very well. And these are evergreen, whereas most of your ornamental grasses are deciduous and go down in the wintertime. All right let's walk across and...

You see a lot of ornamental grasses here, more miscanthus and these is typical of some of the hybrids. And the hybrids range anywhere from three foot tall up to seven foot tall, and again everything we've got over here is a non-seeder. Now behind us is a new uh grass we haven't talked about. This is the genus Sporobolus. There are native sporobolus all around US. It's a wonderful US native. This is Sporobolus airoides. This is one that, excuse me, this is wrightii. Sorry, wrong name. This is one we've grown for years, and this is a Southwest species. So, this grows all the way from really up in Utah all the way down through Arizona and New Mexico. It's been absolutely fabulous for us, just sort of a native counterpart to something like a pampas grass or cortaderia. So, I think these are excellent and they've proven wonderful in the garden. Now if you can see right through there with the plumes, this is another pennisetum, but that is a different species, that's Pennisetum orientale, and this is a huge one. This one, this is one we named ‘Tall Tales’, introduced 25 years ago. This one gets up six foot tall and blooms non-stop from spring till fall. There's not many grasses that can do what that one does, but that requires a big space. If you don't have a 12-foot-wide space that's not your plant.

Now here's one of those that I mentioned earlier. This is the genus Muhlenbergia. This is the plant everybody knows is Muhlenbergia capillaris. It turns out, it's not Muhlenbergia capillaris. When Patrick came on board with us in March, he's like “can I get you to change this?” I said, “I've been trying to tell people for years”. What happened, this originally got misidentified by a taxonomist in Florida and then wound up in the commercial trade as Muhlenbergia capillaris. It is not, it is Muhlenbergia sericea. So, if you've ever been to Charleston and seen the hand-woven baskets there that they make, that's what this is. It's made out of this plant. So, it is a muhlenbergia, it's just not capillaris. It is a great plant.

The plants we find in the trade... after about five years you need to really divide them, because if not, the flowering really declines. In the wild this is a fire species plant. It has to be burned and so in the gardens we typically don't go out with the flamethrower. So, you need to do the same thing by digging it up, dividing it and then replanting it. And we would do that in the fall. We haven't talked much about dividing, so that's always an issue with ornamental grasses - they can be a little tough to divide, especially the larger ones. We typically recommend you do your best work dividing in fall. They can be divided at other times but fall - winter is really a great time to do that. And before you divide, cut the plant back within six inches of the ground, and don't try to dig the whole plant up, you know, it'll beat you to death. But once you cut it back, get an axe and just go right from one side right through the middle and then do the other side, and do it in quarters. Then it's really easy to take a quarter of the plant up and move it around. Without that, it really takes some pretty strong beefy people to divide a grass. Carex is another one, do not divide it anytime except late fall and winter. Bamboos - late fall and winter. If you tried to divide a bamboo in the middle of summer - it is dead. Same for carex. So, you divide them, they're easy, as long as you do it the right time of year. Now over here is one of my favorite miscanthus. We just blogged about this one, this is Miscanthus transmorrisonensis. So, everything else you've seen pretty much is one called Miscanthus sinensis, which means from China. Transmorrisonensisis a re-bloomer, it's the only re-bloomer in the Miscanthus. It just blooms, and blooms, and blooms, and blooms for months. I’ve grown that 35 years, had zero seedlings. It's an extraordinary plant. But right now, nobody wants to grow Miscanthus, because they read online, they think “Oh my God, this is horrible plant that's going to ruin the world!”. We have to be so careful what we read. Again, more different miscanthus.

And you can see, if you look back, one of the shorter miscanthus. See there's one that's only a three and a half feet tall. So, you really can fit those, there's just not another grass that has the plumage quite like that. It is fabulous as a dry cut in the house, that's just it's one of the best grasses to use ornamentally for cuts.

So, we looked earlier at some of the panicum. This is another panicum, one of the taller ones. This one has not held up as well. We're really looking for, in terms of what makes our catalog, it has to stay upright, anything that flops over like that, that's just not going to make it. This looked great up till recently, but that doesn't meet our standards. Still, it's a great plant. And then again, another different one here, doing a little better.

Up here on the right, another muhlenbergia this is lindheimeri. That's an excellent plant. That thing from mid-October there's no grass that's close to that. It's… I put that in my top ten. And then a miscanthus behind it. Really interesting grass here, this is an Eragrostis, another genus. This one I originally collected down in Georgia on the side of the road, and I thought this was really neat plant and sent it to a taxonomist. I'm not a grass taxonomist, that's a whole another world. And he ID'd it as Eragrostis elliottii which is a native species. So, we started selling it and then Proven Winners picked it up and it's now sold all over the world is ‘Wind Dancer’. Turns out, it's a South African species, that was planted on the roadside for stabilization, so it's not at all a native. Still a great plant. It does seed around a little bit, but beautiful powder blue foliage early in the season. So really great, but if you see that in your stores, now you know the rest of the story.

And you'll see some more of the late flowering Muhlenbergia. And that's what's really great about having some that stagger their flowering times is these texturally look wonderful now, but you've still got another month, month and a half before they start flowering.

Cryptomeria… Cryptomeria

Nope, Cryptomeria 'Knaptonensis'.

So, you see more texturally how these muhlenbergias look. This is also lindheimeri that will be blooming much later, so I just love the texture of the foliage. Now here's a little different twist on a Miscanthus. This is Miscanthus giganteus and obviously for the height and a beautiful, variegated form and just coming into plume right now. So, there's really so many different forms, sizes. Another variegated Miscanthus down here in between the giant asters.

Now if you look up above you, this this is an example of an extreme in the genus. This is also a fountain grass or Pennisetum. This is one from Africa. This is Pennisetum ‘Oceanside’. It's just starting to come into bloom now, with the plumes way up there. So, this is about a 12-year-old patch. So, it does spread a little bit, but that's again 12 years, that's not excessive. But that's one, if you got a neighbor, you know, maybe got a bunch of used cars you want to block. Ornamental grasses can be fabulous for that.

This is Jasper (cat). Jasper missed out on the start of the tour. So, another great one for large areas is this clump sitting right across here. This is the genus Saccharum. If you know sugar canes this is a perennial hardy sugar cane. This is Saccharum arundinaceum. The plumes are just starting. The plumes on this are cotton candy pink. They will open up in about another two weeks. Extraordinary grass. Again, you got a neighbor you want to block, it doesn't take many of those to really make a solid screen. So that's again in my mind a very exceptional ornamental grass.

And this will get you a little closer to one of the clumping bamboos that like cold and hate heat. This one we almost saw earlier, that's the genus Fargesia. So that's the mature height on that. That's never going to get to be a big thing. So those are really incredibly well-behaved options for the ornamental grass world. So, I'll stop here, do we have any questions?

It's a lot of options, there's a lot more we haven't seen, so please explore around. There's a lot that looks really good this time of year, but just there's nothing quite like the grasses. And come out here in early morning, late evening and just the plumes just, are just incredible on those that do the plumage in fall. Questions?

Q: What is the grass that grows on your property along the road?

A: Along the road? Oh, in front of! If you come in and you pass our house, before you get to the nursery, that is the Muhlenbergia, it's the white version of the non-capillaris capillaris and that's one called ‘White Cloud’. That's an extraordinary plant. If you haven't grown that... If I had one ornamental grass to grow, that would be it. There's just nothing quite like that plant. It flowers later than the pink by usually three to four weeks. So, for us, mid-October it just explodes with this just massive cloud of white. It's pretty darn incredible. And like I say, you'll see a lot more Genera in the garden. Hakonechloa is one you see in magazines a lot, Japanese Forest Grass. Most of the clones don't take our summers but we have found a couple now that do very well here. And you'll see some fairly old clones. That's a woodland grass. And they're right up in this garden, not too far over there. Any other questions on grasses?

Okay, thank you...Yes?

Q: Are the Carex woodland grasses, are they the ones that grow in the shade?

A: Yes, exactly yes. And again, most of the Carex, I'd say about 50 to 60 percent of the Carex, prefer shade, and then about 40 percent prefer Sun. So just because it's in a particular genus you can't make assumptions on it likes this, because all the others like that.

Q: What about a grass for Richmond? A smaller grass…

A: A grass for Richmond? You are a little cooler than we are, summers are very similar, so I'd say pretty much anything that we can grow here is going to do well for you. Considered the zone, you're on the 7a-7b line, we're on the 7b-8a line, yeah. I mean that can change. Yeah?

Q: Hey Tony is there a good Carex for dry shade?

A: Carex for dry shade. Yeah, one of our favorites is Carex gentilis, that does really look well. That's actually one we brought back from Taiwan, that is, and that's the only Fall blooming Carex that we grow that's pretty incredible. Radiata would also do well, that's a native one. We've got a collection from Halifax County, that would do really well. Some like wet, some like dry of the Carex, so you do need to just look, and we have that on all the signage, does it like wet or dry. But radiata would be a fantastic native selection. Other questions? Okay, you all enjoy! We'll be out in the garden if you have more questions. Thank you very much.

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