combining grass & perenials

I want to use native grasses and perennials for a slope near a road salted highway that faces due east. Dry soil in full sun, zone 5, NH. From research I've narrowed it down to Little Bluestem and Panicum virgatum. I want to go with a purple and yellow color combination. Will these grasses compete with each other? Would I have to re-sow each year? Is purple coneflower native to New England? I see it growing in front yards everywhere. Any native yellow or purplish perennials you'de like to suggest?

Is broom sedge (Andropogon virginicus) native to the NA continent? To New England?

One would automatically think that switchgrass being a much larger and taller plant than Little bluestem, that it would outcompete and smother the Little bluestem. But seeing as switchgrass is native to tall grass prairies that are generally more moist, and Little bluestem (a mid grass) native to drier climates comparatively, I wonder. My guess is, that in the end Little bluestem would do better.

There must be some more tolerant to salt than others, but I just don't know. But for dry, in general you will find that anything native to mid grass prairies will do better than those native to tallgrass prairies. Mid grass ecosystems may have alkaline soil and could be more adaptable to road salt, where as tall grass praires are never alkaline in America.

Purple Coneflower, Pale Purple Coneflower and Yellow Coneflower are all native to Northern United States and Canada. Here are two websites you can go to get info on US native plants: http://plants.usda.gov/
or Dr. John Hilty's site at: http://www.illinoiswildflowers.info/
Although Dr. Hilty's site is on Illinois plants. We are in the same zone 5a.

Ratibida pinnata (yellow coneflower) is tall and would go well with Little Bluestem and other grasses. If you'd like some seeds I could check my plant for seed heads.

Diana

Thanks Leftwood. I am amazed about how much there is to learn! It is so helpful to know the reason why the right plants work. And thanks Diana for the offer, but I'm not yet ready to plant because currently the area is well covered with thatchy lawnand as a newbie I was thinking I'de start after the spring thaw. So here is the next question, do I remove the lawn and then seed and plant? Or can I just sow the seed into the lawn? .
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I don't know how big an area you are thinking of seeding, but you could start with just a small area first by using heavy duty landscape fabric, (not the flimsy plastic stuff) and secure with many ancor pins. In the Spring when you're ready to start planting, the lawn grass below will be good and dead. You can then pull off the fabric, loosen up the soil with a heavy rake and plant your seeds, or dig holes for purchased plants. You'll have more success if you start with a clean slate. No competition with established lawn grass. Otherwise you will end up with a patch of overgrown lawn and weeds that you can't mow because its mixed with your new plants. Picture your pretty little Bluestem grass trying to compete with Burdock and Thistle and all their prolific relatives. Oh, the horror of it!! Ha!

Good luck, and I'll keep some seeds in the fridge in case you need them in the Spring. I have lots of Purple Coneflower seeds also.

Diana

Thanks Pastime, I may take you up on that later. The area is about 90 sq' I've been having so much fun driving around noticing all the coneflowers I see in people's perennial gardens! I ventured over to DG's coneflower forum to aquaint myself them.

With the onset of cool weather, I'm not sure everything would be killed by spring, but at least well on the way. Anything that might be still alive would easily and quickly be killed with a quick spray of Round Up.

Ratibida pinnata is a favorite of mine. Needs poor soil and dry conditions or it will grow too lush with too many flower stalks (who would've though?) that then splay out. The best grown plants I've seen only have one to five flower stalks. Root competition, like from the bluestem is a plus too.

Thanks leftwood, I'll add that one to my list of potentials. To kill the present lawn, would it be too late to cover after the snow melt? I'm thinking that would also help kill off the weeds.

The problem is temperature. The colder it gets, the longer plants can survive under adverse conditions. If you wait, plants (the grass and weeds) will have had all fall to store energy in there roots to survive long into the spring without detriment, and you want to plant seed as early as you can. The grass, etc. would survive well into mid May.

Remember how in chemistry we learned that chemical reactions generally slow by half with every 10 degree reduction? So that means you need to double the time to wait for plant death every 10 degrees. Definitely a bad idea to wait. Do it today if you can. No, do it yesterday. But if you are not averse to using a chemical like Round Up, you can do that on a warm day in early May, and plant the next week. Or spray on a warm day (65F or above) in Sept/Oct.

Thanks Leftwood, this is helpful info. My concern is: if I go ahead and kill the lawn this fall will I have detrimental erosion during the spring thaw? I don't want to lose soil, although the slope is walkable. Maybe I'm overly concerned with soil erosion? Also, I'm sure our first frost should be in about 3 weeks, would that be okay for sowing grass seed? I'm not big on herbicide use, but I went ahead and used one to kill off the invasive bamboo that had spread out in a 15' diameter. (Ah, but that's for another DG forum.)

Of course, we don't have that problem with bamboo here in Minnesota. We're lucky if we can keep it alive! But chemical means are the only way to kill a vigorous bamboo, IMO.

No need to worry about erosion. The thatch and dead roots will not have time to decompose. Soil will still be knitted together. If you use Round Up, or any other glyphosate product that says you can seed in a week, that will be fine. Cool season grasses can germinate at even at 35F soil temperature. A hard frost might bring the soil temp down to 50F. So no problem. However little bluestem is a warm season grass. Planting this fall will probably be of no advantage, because it will probably not germinate this fall, and instead come up next spring anyway. But you could still seed this fall if you wanted to. If it were me on that hill, I would wait until very early next spring, as surface seed does have a tendancy to float and wash.