N-fix 5: Lespedeza

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.

Winter Lespedeza. Photo © Chris Evans, River to River CWMA, Bugwood.org
Winter Lespedeza. Photo © Chris Evans, River to River CWMA, Bugwood.org

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.

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Lespedeza thunbergii ‘Alba’ in my neighbor’s garden. The gold in the background is a variety of black locust (Robinia pseudoacacia).
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My own little ‘Gibralter’ with the resident aster.

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.

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‘Gibralter’ nearly finished with flowering in my Neighbor’s yard.

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. Here is an excellent example

Overall, lespedeza is quite a diamond in the rough with whom I’m pleased to keep company.

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7 thoughts on “N-fix 5: Lespedeza”

  1. Hey, I’m planning to grow lespedeza bicolor in Z6 in order to provide summer forage for bees. I’ll probably use it to fill out the space between elaeagnus bushes, thus making a super nitrogen team 🙂

    Were the specimens you are familiar with frequently visited by bees?

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    1. You know, I don’t recall noticing very many bees on those flowers. I saw some, but it wasn’t covered in them like the Heptacodium. It is very late blooming, and in my climate usually gets nipped by frost before it can even finish.

      I would be very interested in hearing how that kind of pairing goes.

      I have heard though that N-fixers will only recruit bacteria if there is a deficiency of N in the soil to begin with. To make a “team” I would actually go for a non-nitrogen-fixing companion for the Eleagnus, since reducing the nitrogen in the ground would result in more bacterial recruitment, and hence more nitrogen introduced to the system. I’m hoping to do just that with the Lespedeza and Panicum virgatum pairing I mentioned. I have seed for the “Cave-in-Rock” variety. Paulownia would also be great if you wanted to coppice/pollard it.

      Either way, thanks for mentioning your plans. I always find them of interest.

      Are you starting your Lespedeza from seed, or do you have plants to separate?

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      1. My original intention was to start it from seed and I have already received the starter package. Later on I noticed that lespedeza is often for sale s an ornamental plant. However, I’m aiming for at least 10 of them so the cost of buying grown speciments would not make sense. Maybe just one as a pilot case to see how it behaves over the year.

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  2. … Also, I read that cuttings made in summer take easily, so should anything happen to the seedlings (don’t germinate, get disease, are eaten / trampled by animals…) the one grown specimen would also serve as a backup for propagation.

    In a similar vein I’ll be trying to grow maackia amurensis from seed but also start with a couple of 2 or 3-year old specimens. In maackia’s case there’s an additional reason for doing so in that, from what I’ve heard so far, maackia would take 6-7 years before flowering.

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    1. I always prefer cutting when I can get them. It has never occurred to me to try that with lespedeza -probably because of it’s herbaceous nature. That would probably work well though. I’ll have to try that myself just to see how it turns out.

      I found morning glories can root. I found one had grown against a leaky pipe shaded by the plant in a greenhouse, and the spot that was touching the pipe had a massive ball of white roots grown out.

      Often it just works best to get plants. Seeds cost less, but after three times of buying a single packet of seeds from some obscure company, you’re three years without a plant, and have in most cases spent more than the plant would have been to begin with. Wise choice to start with plants of Maackia. I’d love to hear how easily the seeds come up though.

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  3. My cunning plan is to introduce maackia to our bees as a substitute for summer forage on sweet chestnut which does not normally grow in our conditions (low flat land). This is my main goal at the moment – lespedeza, caragana and the elaeagnuses are supporting players. There’s also evodia of course, and paulownia and catalpa speciosa, and koelreutheria, but for some reason I’ve got my eye chiefly on maackia. I hope it works out.

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