Phaseolus coccineus
Was sind Prunkbohnen (Phaseolus coccineus) ?
Breeding hardy perennial beans
Prunkbohnen, auch als Scharlachbohnen, Phaseolus coccineus oder Käferbohnen bekannt, sind eine wunderschöne, kletternde Pflanzen, die hauptsächlich als Zierpflanze verwendet wird. Sie stammen ursprünglich aus Mittel- und Südamerika und sind bekannt für ihre langen, seidenartigen Blüten, die in lebhaften Farben wie Rot, Rosa, und Weiß blühen. In Österreich werden sie auch als Käferbohnen bezeichnet.
Prunkbohnen sind eine Art Kletterpflanze und werden oft an Pergolen, Rankgittern und anderen Strukturen angebaut, um eine grüne Wand oder einen blühenden Vorhang zu schaffen. Sie werden auch häufig in Töpfen und Kästen angebaut, um Terrassen und Balkone zu schmücken.
Neben ihrem Einsatz als Zierpflanze, können Prunkbohnen auch als Nahrungsmittel verwendet werden. Die grünen Hülsen der Bohnen sind reich an Vitaminen und Mineralien und können gekocht gegessen werden. Die trockenen Bohnen können ebenfalls gekocht und als Beilage oder in Suppen verwendet werden.
Die Prunkbohne ist eine ausdauernde Pflanze und kann in den meisten kühlen und warmen Klimazonen gedeihen. Sie bevorzugt vollsonnige Standorte und braucht regelmäßige Bewässerung, um gesund zu bleiben. Die Pflanze kann aus Samen gezogen werden und wächst am besten in gut drainiertem, leicht saurem Boden.
Insgesamt sind Prunkbohnen eine wunderschöne Zierpflanze, die nicht nur Farbe und Textur in den Garten bringt, sondern auch als Nahrungsmittel verwendet werden kann.
Breeding
Phaseolus coccineus
I read in the past that Phaseolus coccineus is normally a perennial, but which was selected for being annual. Some perennial forms of Phaseolus coccineus produce large edible tubers. Its native range is from Central to South America.
I managed to find a landrace from its most northern and probably most cool-climate range. It is grown by the Tarahumara people in the Sierra Madre mountains at nearly 2400m altitude. They have cold and wet winters in this region with snow and -20°C.
A local grower told me that this landrace came back from its root even after severe cold and wet winters.
I planted the seeds in my region in Germany and here is what I found out:
The plants were healthy and vigorous. They bloomed a lot and didn't get any diseases.
There were very few seedpods forming on the first generation of flowers. I don't know exactly why? But I have several hypotheses. Maybe someone else has more insight into the topic.
a) Pollinators: I learned that it is pollinated in its natural habitat by hummingbirds, and there are no hummingbirds in Germany
b) Bad climate conditions: We have a very different climate here than in its natural habitat. We had a hot ( 37°C) and dry summer, that's probably something the plants didn't like and they aborted fruit pods.
I also did dig out the roots which were not thick tubers as I expected. There were some thicker roots but nothing really big. This may be due to the fact that even as it is a landrace it is still grown as an annual in Mexico.
The plants pushed out a big second wave of flowers in late summer, early fall. Those produced more seedpods than the first ones. Unfortunately, the seeds didn't ripen entirely before the first frost hit. I did gather the still green seedpods and I am going to try to let them ripen a bit more indoors. For now, I have maybe 50 mature seeds.
I distributed those seeds and leftovers from the original seeds to growers all over Europe to see how they will do in other more favorable climates.
Future projects
If those plants show to be reliable perennial and cold hardy they can be crossed with modern Phaseolus coccineus varieties to get a high performing perennial bean that's adapted to European climates. In a further step it can also be crossed with the common bean Phaseolus vulgaris to introduce the perennial trait into common beans.
If this accession fail to be perennial or to be cold hardy further research needs to be done to find a suitable source for perennial cold hardy beans. A field test of several hundreds of accessions that are available in European genbanks would be the fastest and easiest way to identify interesting cultivars.
