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Nitrogen Fixer - Need Suggestions

 
E. Elkins
Posts: 22
Location: North Carolina, USA (Zone 7B)
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I'd like to add a nitrogen fixer to an established area that includes small fruit trees and perennial flowers. Here are my constraints

*Mature size needs to be under 2' to 3'
*I'd prefer a perennial that's hardy through Zone 7B so I that won't have to replant
*Clumping rather than spreading
*Needs to be heat (90+ F) and drought tolerant
*Must tolerate heavy clay soil

I'd really like a compact shrub, but I'm not finding anything suitable. I've also looked at perennial cover crops, but the only good option that I've come across is Birdsfoot Trefoil. Does anyone have any other suggestions? I'm hoping that I've overlooked something...
 
Tyler Ludens
pollinator
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Posts: 8974
Location: Central Texas USA Latitude 30 Zone 8
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I've been looking at Baptisia Blue False Indigo or Wild Blue Indigo. There is a large-growing form to 4 feet Baptisia australis and a smaller relative Baptisia minor.
 
E. Elkins
Posts: 22
Location: North Carolina, USA (Zone 7B)
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H Ludi Tyler wrote:I've been looking at Baptisia Blue False Indigo or Wild Blue Indigo. There is a large-growing form to 4 feet Baptisia australis and a smaller relative Baptisia minor.


I really appreciate your reply -- I'd dismissed Blue False Indigo because I thought it was too large, but I appear to have been mixing it up with Amorpha fruticosa (aka Desert False Indigo or Indigo Bush). Baptisia minor looks especially interesting. I found one nursery that suggested it as a good lupine substitute for the south, so it could be just what I'm looking for...
 
Toby Hemenway
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Baptisia was the first thing that came to mind. It's a great plant. There are small indigo varieties that you should research, and Amorpha should also be a good choice; I've kept it pretty small.
 
E. Elkins
Posts: 22
Location: North Carolina, USA (Zone 7B)
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Toby Hemenway wrote:Baptisia was the first thing that came to mind. It's a great plant. There are small indigo varieties that you should research, and Amorpha should also be a good choice; I've kept it pretty small.


Excellent -- thanks for seconding Baptisia, Toby. I did some research last night, and Baptisia minor looks to be just about perfect. It's a shame that it takes it a few years to bloom (or so I've read) -- the flowers spikes are lovely. I'll take a closer look at Amorpha, as well.
 
mike mclellan
Posts: 93
Location: Helena, MT zone 4
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I have used Baptisia australis in a more formal flowerbed setting. It was absolutely bulletproof. Tore out all the surrounding flowers eventually but didn't have the heart to attempt to dig both of them out and likely kill them. Their taproots were quite deep. I didn't water them the last three years I lived there and it didn't faze them at all. I realize this was in a setting far different from NC ( central Wyoming where the wild wind howls constantly and the UV is high due to the elevation) but I was greatly impressed by its tenacity and beauty.

Have you also considered lupine? There might be a variety suited to your area.
 
E. Elkins
Posts: 22
Location: North Carolina, USA (Zone 7B)
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mike mclellan wrote:Have you also considered lupine? There might be a variety suited to your area.


Hi, Mike. I'm glad to hear that Baptisia was a good performer for you. The fact that it did so well in rather harsh conditions is encouraging. I considered lupine, but gardeners here in NC report mixed results -- some can grow it successfully but many can't. In fact, Baptisia is a commonly recommended lupine substitute for the southeast. Nonetheless, I have some lupine seeds that I purchased on a whim last year, so I might give it a try.
 
Jordan Lowery
pollinator
Posts: 1528
Location: zone 7
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its not a perennial, its a biannual, though it can be perennialized easily. is white sweet clover. small bushy plant to about 3ft, some rare specimens can get to 5ft with good conditions, but will not grow so dense it hurts neighboring plants or steals sunlight. it can be chopped and dropped for mulch, many other uses as well.

it is considered a pretty bad weed to most people though, and kill it on the spot. despite the fact it is a GREAT nitrogen fixer.

bush lupine is also good and doesnt get much bigger than 5ft in its mature stage, and it makes wonderful honey and smells absolutely amazing when in bloom.
 
Matthew Nistico
Posts: 269
Location: Clemson, SC ("new" Zone 8a)
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@E. Elkins - Baptisia sounds like a winning candidate. It meets the criteria you posted, and the Wild Blue Indigo variety, at least, is native to boot. (Are all Babtisia native?) Others here have also recommended Amorpha, which would surely also be a great candidate. I have added Lead Plant (Amorpha canescens) to a native meadow that I am starting and building into a food forest ...or perhaps a food savannah would be more accurate. Wikipedia provides that "The lead plant (A. canescens), a bushy shrub, is an important North American prairie prairie legume. Lead plant is often associated with little bluestem (Schizachyrium scoparium), a common prairie grass. " There are several bluestem species seeded in my meadow. I wish I could report on how the combination has performed for me, but I'm only just getting it all established.

I post here today because in looking up some info discussed by others in your thread I noticed for the first time another Amorpha - Amorpha georgiana - with the common name Georgia False Indigo. With you in NC mountains and me in SC mountains, I thought this might be a promising candidate from a bit closer to home. Has anyone grown it? Can anyone provide info and anecdotes?

~ Matthew N., Southern transplant
 
Ivan Weiss
Posts: 172
Location: Vashon WA, near Seattle and Tacoma
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I'll probably be planting amorpha, but the nitrogen fixer that really excites me is galega orientalis. This has potential as a nitrogen fixer, a bee plant, a fodder plant, a chop and drop mulch plant, and a compost plant.
 
Brenda Groth
pollinator
Posts: 4434
Location: North Central Michigan
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some other options i can think of right off the top of my head are lupines, runner or bush beans, peas, clover, sweet pea
 
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