In the last N-fix I touched on the use of autumn olives (Eleagnus umbellata) in reclaiming strip mines. I wanted to continue this theme with autumn olive’s southern counterpart lespedeza.
Despite its similar occupation, Lespedeza bicolor is very different from autumn olive. It’s not actinorhizal, it’s a legume, the more common kind of N fixer. It’s hardly woody, it’s herbaceous, growing a full 6-12 ft every year only to die back to the roots in winter in my climate. Its root system is rather shallow, and quite fibrous. It’s a medium level nitrogen fixer, more in the range of amorpha. About the only characteristic it has in common with autumn olive is it grows like crazy in soil worthy of horror movies.
It’s been an invasive species that colonized and then poured out of the southern strip mines for decades. Lucky for us in the north, and probably the reason why I’ve never seen a lespedeza in any strip mines around here, lespedeza needs a long season to ripen its seed –a minimum of 160 frost free days.
You might wonder then how it has a range far in to Canada? There are exceptions. In fact the USDA selected for fast maturation of seeds in L. bicolor the most notable being ‘Natob’ which ripens seed a whole month earlier.
There’s an interest in the plant making seed because it was intended to feed wildlife such as quail. For this, and grazing animals the USDA mentioned switchgrass (Panicum virgatum) makes a good companion. Switchgrass grows very tall during hot weather so ditto for harvesting mulch.
So far I haven’t bothered with L. bicolor and have stuck to the more showy but similar L. thunbergii. My Neighbor has two cultivars, ‘Alba’ and ‘Gibralter’ in her yard, well over a decade old, and has never had them reseed or set seed on the ‘Gibralter’ as far as she can tell. Neither is a hybrid, but seed doesn’t seem to ripen for her.
The two lespedeza in my food forest are side shoots from her ‘Gibralter’ I transplanted. Unfortunately they weren’t successful in growing to six foot like hers; they topped off and bloomed very prettily at three feet this year. I assume they’ll get that size once well-established.
I would like more though, because lespedeza’s drastic change in height every year allows for a lot of niche planting with tons of room available in spring, then partial shading in summer, and an all out eclipse in fall. Then too, the canes will last through most of the winter, creating a wind break for more tender plants.
The only possible problem could be the shallow root system. I haven’t experimented much with it, so can’t say how much it suppresses nearby plants, and my Neighbor mostly has other shrubs around hers. Best bet is probably spring bulbs such as camassia closest to it. Then a little further away where sun will last until at least mid summer you could plant Turkish rocket which is very taprooted and doesn’t do much after May. Good King Henry has about the same schedule but its roots don’t pierce quite as deep.
Two of our native species, L. capitata and cuneata are both much shorter, capitata topping off at four and cuneata at a two feet usually. Cuneata is considered an invasive species in some states though, such that its sale has been banned in them. I don’t plan on growing them unless included in a pasture mix.
I prefer ‘Gibralter’ not only for its biomass, but its beauty. It has very deep pink color with an almost iridescent blue and purple hue on the tips if you look close. Often it’s placed near a pond in ornamental gardens to give the effect of a green and pink waterfall.
Overall, lespedeza is quite a diamond in the rough with whom I’m pleased to keep company.