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Rose Acacia / Bristly Locust (was: Please help me ID this flowering shrub)

 
Dan Boone
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Hi! I've got an oak tree at one edge of my yard and the area under it has become a wild jumble of shrubs and grasses that I am slowly clearing and planting with more useful things. (It's not as shady as you'd think since the oak mostly blocks just the early morning sun.)

However, in the space I want to use, I have eight or ten flowering shrubs (ranging in height from knee level to about eight feet tall) that I don't know what are. Some of them are in my way and may need to be cut down or transplanted (or, depending on what they are, I may need to change my intentions for the space and leave them.) The shrubs are clearly of some value; the flowers are beautiful and sweet-smelling and attractive to bees. This morning despite strong winds, there was a bumblebee the size of my thumb working the blossoms -- seriously the largest bee I have ever seen. You can understand why I want to make this ID.

The photos below are not awesome; the wind was really moving the shrubs when I took the pics. But they may be good enough. I'm pretty ignorant about flowers so I'm hoping this will be so obvious people will wonder how I didn't already know. One feature that may not be obvious from the pics is that the younger growth of stems (not the main stems of the larger ones) is covered with copious hairs that make the stems look like they would be painfully thorny. But the hairs are not in fact stiff or sharp or painful to touch. The oval leaves and hairy stems remind me a lot (visually speaking) of the wild roses that grow in Alaska (Rosa aciculariso) but the flowers are radically different; indeed, they almost look leguminous.

Enough babble, onward to the pictures! And thanks for any help you can provide.

mystery-flower-01.jpg
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Mystery shrub; plant in lower left is a young sunchoke
mystery-flower-02.jpg
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some leaves and flowers
mystery-flower-03.jpg
[Thumbnail for mystery-flower-03.jpg]
closeup of leaves, flowers, hairy spines, and not-fully-opened buds
 
Ken Grunke
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I googled "purple flowers hairy stems" and came up with Rose Acacia after a few minutes. This looks like a pretty close match:
http://www.rogerstreesandshrubs.com/gallery/DisplayBlock~bid~8131~source~gallerychooserresult.asp
 
Jennifer Wadsworth
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Definitely looks like a legume!

I think Ken might be right: http://www.kew.org/science-conservation/research-data/resources/legumes-of-the-world/genus/robinia
 
Dan Boone
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That's it! Thanks, folks. Specifically it's Robinia hispida, aka Rose Acacia, Bristly Locust, or Moss Locust. It's a close relative of the Black Locusts so beloved by permaculturists, and its nitrogen-fixing ability seems not to be in dispute like the other leguminous trees I have (honey locust and redbud). So it's a shrub I do want, if perhaps not quite right in that spot.

Very much appreciate the help!
 
Miles Flansburg
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Dan Boone
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I have edited the thread title to reflect the successful ID. One reason this was so helpful to me is that I have a color vision deficiency; I would have said those flowers are "blue" but I live in a world where there's no such thing as purple or pink, so I've learned the hard way never to utter the word "blue" unless I'm prepared to be laughed at. It makes flower ID even trickier than it already is, believe me.

Now that I know what it is, here is what I've learned about the plant. Search tells me it's never been discussed in detail on Permies.com, which is a bit of a surprise, because it's got a lot of positive qualities. It is leguminous, it's said by the USDA to be nitrogen-fixing, and because it suckers from exposed roots it's especially good at erosion control in and near eroding gullies, for which it is widely used. Growing in zones 6 to 11, it will tolerate poor and dry soils and is usually not recommended for decorative plantings (despite being a quite beautiful shrub) because it spreads rather aggressively (some states consider it invasive).

Downsides are its invasive spreading/thicketing nature (so it won't play well with others) and the fact that it's apparently not edible in any respect; it's generally described as being poisonous in all parts, although the Cherokee supposedly made some use of its roots for a toothache medicine.

http://en.wikipedia.org/wiki/Robinia_hispida
http://plants.usda.gov/factsheet/pdf/fs_rohif8.pdf
http://www.illinoiswildflowers.info/trees/plants/bristly_locust.htm
http://www.finegardening.com/plantguide/robinia-hispida-bristly-locust.aspx
http://blog.lib.umn.edu/efans/ygnews/2009/07/rose_acacia_-_a_shrub_with_sho.html
 
Dan Boone
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Miles, I'm not sure you can't grow it. Although I got my "zones 6-11" info from one of the garden/nursery links I posted, the USDA flyer I linked says it's widely used by highway departments in the Northeast, although it "may winter kill above the snow" in Northern Maine. Maybe 6-11 is the limit for growing beyond shrub size? It might be worth an experiment.
 
Miles Flansburg
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Might have to try it someday. Maybe in a sunscoop.
 
Peter Ellis
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That looks to me like a pretty good choice for a "nurse plant" when starting up a food forest system. Lacks some of the functionality that some others might provide, but looks like it should be a good insectary along with being a nitrogen fixer, visually pleasing with those lovely flowers. And since it is not edible, when it comes time to chop it back and make it give way to the next round, I wouldn't feel like I was losing something

Wonder about growth rate for chop and drop. Need to make a note to keep this one in mind.
 
Brian Cady
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found a seed source: F. W. Schumacher has seed availble: https://www.treeshrubseeds.com/specieslist?id=380
Here's a 2-pge descrioption: plants.usda.gov/factsheet/pdf/fs_rohif8.pdf

Has anyone used this as a short-lived nurse crop for planted trees? Has anyone done business with F. W. Schumacher?
I imagine this would fix nitrogen, then get shaded out by taller trees when the tree canopy closed.
It's supposed to only cast light shade itself, and to be winterkilled in zone 4 above the snowline. It's native in Tenn. and NC.
 
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