What zone and climate are you in?

Albizia julibrissin (hardy silk tree) is very ornamental to my eye. Unusual pink flowers for several weeks in the summer that attract butterflies and hummingbirds, nice umbrella shaped spreading canopy, dappled shade underneath, and leaves that fold up every night. In zone 6 it is on the edge in terms of hardiness. In warmer zones, it can be invasive, spreading a lot be seed. There's a lot of venom for that tree in the South, and it will likely show up in response to my posting! Search this group for a taste of what I'm talking about. It is also susceptible to a wilt disease that can kill it in a season.

Kentucky coffee tree is nice looking. Nothing too showy, but just a nice shape IMO.

Mesquite tree is another good looking one, but it's limited to the desert southwest AFAIK.

Alex

around here maybe honeylocust. most legumes have significant drawbacks like spikies or messy pods. I think there are some non-legumes like alder that can fix too, but they have drawbacks too (short lived).

There might some tropicals, but I don't know anything about that.

alnus glutinosa 'imperialis' is stunning (RHS Award for Garden Merit)
alnus incana 'pendula' is fantastic
alnus glutinosa 'pyramidalis' is an excellent substitute for lombardy poplar

otherwise a male selection of Kentucky Coffeetree ('Espresso')

Kidneywood (Eysenhardtia texana) and Goldenball Leadtree (Leucaena retusa) are nice small flowering options if you're zone 8 or warmer.

Here is a link that might be useful: Goldenball Leadtree, Wahootree, Littleleaf Leadtree, ...

Honeylocust, while a legume, does not form root nodules, which casts its nitrogen fixing ability into doubt. Some say it fixes nitrogen anyway, but I don't think this is really settled yet.

Bristly locust. Well, they're not pretty & they sucker profusely, but they make the greenest grass around them.

can we ask why you need a tree to do this???

ken

What about redbud (cercis), that's a pretty-looking legume but does it fix nitrogen?

...does (redbud) fix nitrogen?

Not according to the USDA PLANTS database.

Here is a link that might be useful: Cercis canadensis plant characteristics

This post was edited by bostedo on Sat, Nov 30, 13 at 10:23

Robinia pseudoacacia can look great, IMO, but I dislike seeing them anyway, at least anywhere north of my location. They're just barely "native" here in the Fox River Valley of WI but a true marauding invasive menace everywhere north, especially in the very sandy areas where it can quite readily displace everything else. Other than that, great trees!! ;^)

+oM

Have always been fond of laburnum and even the widely detested Mount Etna broom (Genista aetnensis). Although more shrub-like than tree-like, I also have a fondness for the various indigoferas (amblyantha, heterantha, kirilowii).

Have always been fond of laburnum and even the widely detested Mount Etna broom (Genista aetnensis). Although more shrub-like than tree-like, I also have a fondness for the various indigoferas (amblyantha, heterantha, kirilowii).

learn me up peeps...

i thought you plant a production cover crop ... which fixes nitro ... such as bean ...

so that the following year... you can till in the roots.. so as to have nitro available for the second crop.. here in my county.. corn ...

every other year.. every other crop ....

one year.. nitro fixer.. the next year.. the nitro user ..

so what is the point of a tree that fixes nitro ...???

i simply dont understand the equation???

an make it simple.. i am a dullard, when it comes to soil science .... as in.. dig hole.. plant things.. walk away.. water occasionally ... no amendments.. no fert.. no nothing.. just water ...

ken

Ken,

Well they drop leaves that are unusually high in nitrogen in addition to the root slough off. If you're on a completely organic lawn program like I am and you're looking for a tree for the front yard, you might as well get a nitrogen fixer.

Kentucky Coffeetree was the obvious choice originally, but then I read a lot of claims that it doesn't actually fix nitrogen. Black Locust is one of the best nitrogen fixers (highest nitrogen content of leaves), and it actually isn't all that ugly. The only concern I would have is seedlings/suckers popping up all over my lawn.

This post was edited by CPTK on Sat, Nov 30, 13 at 16:49

Lack of fall color aside, I rank black locust highly pleasing to the eye. Especially in that sterile, sandy ground where it seems to do best. But yeah, they can sure-root sucker. Little sharp thorns aren't fun either, should you ever find yourself pruning one.

Flowers are cool too. But again, in areas where they're displacing native N. hardwoods and mixed forests, not good.

+oM

Maackia amurensis is nitrogen fixing but might be a bit small for you since you were considering Kentucky Coffee Tree, sure is pretty eitherway.

I like your thinking on this one.

Alders are also capable of nitrogen fixation.

Since we don't know where CPTK resides, perhaps half of our suggestions are useless. That said, I'd not pick a yard tree based on that criterion-whether or not it fixes nitrogen. Even in an organic program, it is easy to supply all the N a lawn needs. So just based on that alone-and it is all we're going on-I'd make my tree selection based on other factors.

+oM

I'm not very fond of alders, but alnus cordata might be the prettiest of them. Thrive on dryer ground than other alders, perfect for a lawn. Not very cold hardy for an alder though, only USDA zone 6A.

completely organic lawn program like I am and you're looking for a tree for the front yard,

==>>> i guess its time to go back to bed .. as i learned my one new thing for the day .. lol ..

my organic lawn system includes .. simply ... mowing back in the grass ... and mowing the leaves in in fall ... i dont even water .... and yes.. it browns for most of july/august ... but then.. i dont have to mow it ...

no.. i dont have a perfect lawn ...

but i gave up the lawn warrior ideal when i moved to 5 acres ...

its green... who really says it needs more nitro.. other than the lawn warrior enablers.. such as the guy who wants to sell you fert ...

you would be better off.. simply not fert'g... in any form.. than planting a locust.. though i cant say the one you mention is the worst of the lot re: suckers ... i was taught to avoid locust in the lawn ....

you would be better served... planting an heirloom deep rooted tree.. like an oak ... that will cool the lawn.. rather than a bunch of carp trees that are less than good trees.. for reasons other than nitro fixing..

BTW.. great tree discussion ... have you broached this with the lawn warrior forum.. if so.. link us

ken

Is Yellowwood N-fixing?

hair,
I have seen some disagreement on Yellowwood. Most seem to think that it does not. Otherwise to me it would be the best option for the OP.

Just wanted to add about Robinia pseudoacacia Black Locust. House I grew up in had ALLOT of them around it, many fully grown. Never had much problems with thorns. At least the once where I lived, seemed to not produce many or any thorns after they got larger. Nothing for fall color, but the trees covered in flowers in spring with their strong scent was just as good as the week of fall color you get with most trees. Just some personal experience.

Arktrees

This post was edited by arktrees on Mon, Dec 2, 13 at 14:53

Black Locusts are nice in flower. However, they get that damn locust leaf miner and turn brown by July, making most of our roadside woods appear to be littered with dead trees.

It only seems to affect them where they form large colonies, solitary trees or small groups generally seem to escape it and look good through the summer.

Hehe, I wish those we've got up here would get that leaf miner! As you can see, my feelings towards this tree are deeply conflicted!

One other item to add to this discussion: A species can and will vary in its characteristics depending on site factors. Thus, a bl. locust on rich, fertile soil may never develop N-fixing ability, whereas the same type of tree on sterile mine tailings may be quite far along in that ability. Of course, it's not really the tree doing this but rather, colonies of bacteria working in concert with the roots of the tree.

+oM

I put my zip code in the original post, so I'm not sure why several replies have stated that they don't know where I'm located.

Also, I'd ask that we stick to the topic of good looking nitrogen fixing trees. Although I appreciate lectures concerning my personal choices from strangers as much as the next guy, this particular forum thread has a specific topic.

Must access memory of physical locations corresponding to all possible zip codes......there, that didn't take too long. Looks like you're in N. Carolina. Must admit though, I had to cheat, both in terms of going back to your OP and looking...and sure enough, that string of numbers is there...and then looking it up. Memory just isn't what it used to be! Sometimes, and for the same amount of effort you just spent yelling at us, you could have simply stated where you're at. Suit yourself though.

That said, I get your point there, Mr. CPTK. In fact, you remind me of me a few times when others have veered off and away from my original question.

So what are you leaning towards? At least, you didn't just drop a question in here, to never return, as in the meantime, we forum regulars go on and on with possibilities. That's happened enough.

+oM

I may be a Mensan, but I'm also blonde. I had no clue the 66441 was a zip code. Purposely planting trees with nitrogen fixing ability was a novel concept to me, and frankly I'm really enjoying watching the thread evolve. It even led me to Google to spend a couple hours reading about projects involving nitrogen fixation in land reclamation.

I thought the thread not only provided a few reasonably good recommendations about attractive choices but a lot of information in which other people might be interested. At least we remained on the topic of trees and nitrogen fixation. We have taken the airplanes with flights of ideas on wilder runways, and the trains of thought to stranger tracks.

Personally I'm appreciative when all aspects of a question (specific or not) pop up, sometimes one learns something, especially from the collective experience of this group.

Hey, sorry if my choice of words concerning the zip code came off wrong. I was just pointing it out. 66441 is actually Junction City, KS.

I was annoyed at one particular post lecturing me on my choice to plant a nitrogen fixing tree. 99% of the posts were great. Thanks for all the suggestions.

The most helpful information you can give us is your USDA temperature zone and your very general location. Most people have that information in their heading. Don't expect us to look that up for you. It's up to YOU to provide as much useful information as possible.

Signed,

7a AL (alabama)