Knölvial – This year's edible perennial

The UN has decided to 2016 is legumes years and in honor of this, the edible perennial group appointed by the rather overlooked knölvialen (Lathyrus tuberosus) to year edible perennial.

Lathyrus tuberosus is a climbing plant that makes beautiful pink flowers by summer. It works well to grow in the woodland garden context. Just like most other legumes knölvialen bind nitrogen from the air with the help of bacteria and thus helps also their neighbors with a little extra nutrition. I have successfully grown it in polykultur with Jerusalem artichokes, korogi (Stachys affinis) and raspberry.

Knölvialen get big, beautiful and fragrant flowers in July and August.
Knölvialen get big, beautiful and fragrant flowers in July and August.

As the name suggests knölvialen grown for their edible tubers. The first year is the brown pink, from the second year, they become almost black, and therefore can be a little hard to find in soil. They grow on long strings, and therefore has a similar growth habit as the related potato bean (American apios), that does not really seem to thrive so well in our Swedish climate. Lathyrus tuberosus got some bad reputation that it would be very low yield, but in my plantations (in a quite easy and humus soil) gave it as much as 400g per square meter. The roots are harvested in autumn or in spring after the frost has passed out of the earth. They can be boiled (20-25 minutes), fried and roasted and tastes a lot like sweet chestnut.

How much bumps I got from an area of ​​one square meter. Not so bad!
How much bumps I got from an area of ​​one square meter. Not so bad!

The tubers are rich in minerals (the nedan) and contains about 1,3 % protein [1,2].

Calcium Magnesium Phosphor Potassium Iron
mg / 100g mg / 100g mg / 100g mg / 100g mg / 100g
Knölvial 92,80 21,82 6,59 154,54 0,75
Potato 5,00 22,00 44,00 379,00 0,31

Lathyrus tuberosus can grow in sun to partial shade and grows about 1,5 m on a seasonally. Ideally, you want it to grow into a humus and soil moisture retention. The most easily propagated by tubers, but can also be pulled up from seed. The seeds then need to be roughened with a file or sandpaper and soaked. Seeds are available from Impecta and plants can be found in our nursery here in Stjärnsund if you are passing.


[1] Turan, M., S. Kordali, H. Rich, A. Dursun, and Y. Sezen, Macro and Micro Mineral Content of Some Wild Edible Leaves Consumed in Eastern Anatolia. Acta Agriculturae Scandinavica, Section B – Plant Soil Science, 53(3): p. 129-137, 2003.
[2] USDA. National Nutrient Database for Standard Reference. 2011., Retrieved 2015.


2 thoughts on “Knölvial – This year's edible perennial”

  • Hej og tak for en god blog! I bought your book and am starting to get to know it. I'm surprised to write that spinach vine (hablitzia tamnoides) likes to stand in the sun?
    Everywhere else will I know, that it should be in the shade, and that it comes from an environment with much shade.

    Is it because your garden is far north??


    • Hi!
      Hablitzia absolutely prefer partial shade in our experience also, but if the soil has a high organic matter content and does not dry out too much or there are moving ground water, it is perfectly possible to grow it even in full sun.

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