I am now about to break my own rule, but like a proper merchant banker I shall retain a clear conscience, if not a six figure bonus. Amphicarpaea bracteata is the hog peanut, a widespread North American legume with a fascinating reproductive system. Of more immediate interest is its production of tasty underground beans,
which can be harvested in the autumn.
In order to circumvent my own rules, I have therefore unilaterally elected to rename Amphicarpaea bracteata "talet" rather than "hog peanut". First of all, it's not a peanut, Arachis, although it does form underground pods. It's recognisably a bean. Secondly the beans are definitely worth fighting over with the hogs. A pod isn't a root, as avid botanists amongst you will have already spotted; this is assuredly an egregious deviation from my mission statement, but just as the first potatoes in Europe were thought to be truffles, I consider hog peanuts to be an honorary root crop. They do grow underground in a rootlike way and are sometimes even erroneously referred to as tubers.
So why talet you may ask? Talet is the name given to the hog peanut in the milpas (traditional cornfield polycultures) of the Sierra Norte de Puebla, Mexico, where it is semi-domesticated, or, perhaps more correctly, an encouraged weed. Seeds are sown with the corn and then harvested and toasted on a skillet when the fields are ploughed at the end of the season.
Surprisingly, perhaps, they seem to grow quite well here. The plants have trifoliate leaves and look a bit like mini French beans. They're actually rather pretty in an understated sort of way. This photo, courtesy of Frank van Keirsbilck , provides an impressionistic sweep of talet foliage.
The shoots will climb up any stems in their vicinity and after a while, long horizontal side branches power out from the leaf axils. These produce thin stalks, like long antennae, that burrow into the ground. At their tips are tiny flowers and each one has the potential to form a bean. These flowers are cleistogamous, that is they never open and are self-pollinated. At the same time, all unbeknownst and invisible, similar shoots are developing underground straight from the parent seed.
Later in the season the aerial flowers appear, first in the form of single cleistogamous flowers, which may go unoticed and somewhat later still as small clusters of open- pollinated (chasmogamous) flowers, with pale lilac petals. So that gives the plant a range of seed types: soft fleshy ones underground from the cotyledonary shoots, similar ones from the long aerial side shoots, both of which are self-pollinated. Then there are the small hard seeds from the aerial flowers, some of which are self-pollinated and some of which are open-pollinated. In a good season the big seeds will survive until the following spring and produce big plants. If things get a bit tricky, the small hard seeds will probably make it through until conditions improve again, perhaps several years later. They may get carried some distance from the original plants during this time. Their genetic variability will show up in the seedlings, some of which may be better suited to the prevailing conditions. If they like what nature dishes up, they'll produce lots of the big seeds once more. The technical term for this botanical bet hedging is amphicarpy. If you understood any of that, well done. I think I'll go and lie down for a bit.
Another advantage of Amphicarpaea is its abilty to fix nitrogen. The correct strains of Rhizobium bacteria for effective nodulation belong to the "cowpea miscellany" (weren't they a progressive rock band circa 1976?). These tend to be absent from British soils, so I just plucked some nodules from my Apios plants, crushed them in water and poured them over the Amphicarpaea plants. It seemed to do the trick with lots of nodules developing afterwards.
There's a closely related species in Asia, Amphicarpaea edgeworthii. The Japanese, who leave no stone unturned when it comes to testing things for edibility, have even investigated it as a potential crop plant. The Japanese name, "yabumame", means, apparently, "bush soy", which is suggestive of innate potential. I had to laugh when I saw a plant growing, oh-so-nonchalantly, right outside the dormitory building in Tsukuba, Japan where I stayed for a couple of weeks in 2007. It was even funnier to step into the greenhouses and see, wholly unexpectedly, oca, ulluco and mashua plants, but that's another story.
I can see talet being grown as a living mulch around root crops, like, oh, I don't know, oca for example, or in a modification of its Mexican cornfield habitat, as a ground cover in a sweet corn patch. At the moment it expends a lot of energy producing long runners that deposit seeds far and wide. Maybe with selection, varieties with shorter runners and bigger yields could be obtained. The abstracts of Japanese papers I've read on the subject seem to suggest this.
Although the plants themselves are frost tender, I have frequently noticed seedlings popping up from unharvested seeds the following May. A tasty underground legume that can actually survive here and emerge in spring - that's no peanut.
Talet apparently needs short days to initiate flowering. As A. bracteata occurs right up into Canada, it's possible that varieties better suited to our long day summers might be found there. Anyone who can provide me with seeds from such northerly locations will earn my undying gratitude and an honourable mention on the blog.
OK, the yields are unimpressive, but this a wild plant. Compare your average King Edward with a wild potato progenitor, say, or a wild carrot with a nice juicy Chantenay Red Core. It's unlikely they'd be mainstays of the British diet had they not undergone rigorous selection for size and taste. No, in my opinion, talet has definite potential. Accentuate the positive: tasty bean, grows well; eliminate the negative: low yield, daylength sensitivity and do mass selection in between.
Another interesting observation, which could be advantageous, is that, in my experience, talet doesn't want to bake in the sunniest spot in the garden. Plants in full sun seem altogether dejected and yellow. Give them a bit of shade and they're big and vigorous. A shade tolerant, nitrogen-fixing bean crop that grows in Britain - Gimme! Gimme! Gimme! Apologies to ABBA, but who'd want a man after midnight when they could spend the preceding few hours munching on handfuls of delicious talet beans from their own polyculture plot?
Double the yield, reduce the excessive vigour and we might just have a really useful new temperate legume crop. What are we waiting for?