Well, so far on my own I have found red clover and fava beans listed as n-fixers that will work in slightly acid soil. Neither of them seems like they will look very good in my north country guild, I don't recall seeing either of them in association with the above mentioned trees, but I guess I need to do a lot more research on my own.

I am aware that very acid soil is a serious deterrant to n-fixation. That's why this whole guild both confuses and intrigues me. All the time I've spent up north in wild blueberry patches I wasn't paying that close of attention to all the plants around on the ground. I do recall seeing ferns, but not much else.

Of course there's always good old manure. Doesn't seem like many of these plants are heavy nitrogen users anyway, although I don't know about cherries.

You might contact Peaceful Valley Farm Supply and talk to them. They have a good variety of cover crops, and could probably make some recommendations. (They also have a paper catalog.) I, too, live in an area of acid soil, and the clovers seem to do well here (and they're attractive to bees).

Sue

Here is a link that might be useful: Peaceful Valley Farm Supply

Thanks for the link. The crimson clover looks pretty! I also was thinking about maybe lupine, but it isn't very hardy here on the border of zone 6, and my urban yard gets hot. Maybe in a few years when the trees get bigger. There are these things called "pea shrubs" or "false lupine" that might work, but they're kind of big. The reason I'm so partial to decorative plants is that my yard is tiny! Everything has to do double or triple duty. I'm also kind of partial to natives.

In Alaska, it would be alder and lupines, the wild blue ones. Lupine seeds are poisonous- be warned in advance. You should also be able to use pea shrubs- check Raintree Nursery. I have a couple of pea shrubs here. Soil pH is 4.5 - 5 so it's definitely acid!

I wanted to follow up on this. I went to a native plant nursery for some of my plants, and while I was there I bought sweet fern because I remembered it from my days of living in the wild and I thought it would look good in the bed. A week ago I was working with a student on N-fixers, and quite accidentally I came upon information that said sweetfern was an n-fixer. And the leaves can be used for tea, although it's not exactly "yummy." I planted one but plan on trying to squeeze in at least one more. It does well in somewhat acid soil.

I just saw this thread, and thought it was a good opportunity to use the excellent plant species matrix in the newly released "Edible Forest Gardens" by Dave Jacke and Eric Toensmeier.

I found the following as herbaceous nitrogen fixers that grow in acid (5-6) or strongly acid (less then 5) soils, and that are hardy in your zone.

Amorpha nana Fragrant False Indigo
Amphicarpaea bracteata Hog peanut
Baptisia australis Wild blue indigo (most acid tolerant on
this list)
Desmodium canadense Showy tick trefoil
Lupinus perennis Lupine

I also found Sweet Fern. I had thought about getting Sweet Fern for my garden, but I think it does not like clay soil.

Good Luck!

Alex

Clay soil, BOOOOO! The bane of most of us SE Pennsylvania'ers. That's why I'm using raised beds, I ammended everything with a mixture of sand, topsoil, compost and lots of peat.

Follow up note: the blueberries are really struggling in my yard. The rabbits ate off all the new growth this winter. Next year I'll need to cage them. I'm wondering if it is even worth it in my tiny yard. Nothing perennial and edible seems to thrive. Not many native things seem to thrive either, since it is so hot and buggy and pest dense in my yard. I have no trouble growing standard herbs and veggies in pots or in the garden though. So far I've had one sweet fern survive and thrive through the winter, and one died. However, the one that died did so in a place that everything I plant dies in. I'm going to have to dig down into that spot this spring and see what gives. I think possibly there is cement down there from an old post.

Any ideas on how to keep my soil tipping towards acid? I have pine bark mulch on the beds. I guess I can works some peat into it every year. Not very sustainable.