Monday, June 04, 2018

Crop summary: Air potato, Dioscorea bulbifera

Eric Toensmeier's Perennial Vegetables first introduced me to this easy staple carbohydrate. Although it's only truly perennial in the subtropics or warmer, I brought a few back to Portland from my first Hawai'i visit. I hoped to cultivate it similarly to a dahlia, overwintering propagules in a non-freezing space to be planted in spring, and yielding crop and more planting stock before the killing frosts. Alas, my precious babies rotted away in our pseudo root cellar before I ever got to plant them, so I didn't get to really make their acquaintance until I moved to Hawai'i.

As the name hints, air potato vines form large (up to triple-fist sized) balls of starch in the air, so no soil disturbance is necessary for harvest. Fortunately, you needn't stare worriedly at the vigorous vine engulfing its 30' living trellis tree, wondering how you'll get to the crop. After the deciduous plant dies back in the fall, the ripe tubers fall to the ground (from November through February here in Puna.) You should ensure that the ground under the vine is reasonably clear of vegetation, or can be hacked down before the tubers start falling, so you can find them with reasonable ease. Once you have them, use them in any way you would potatoes. Peeling is optional.

One year yield
A yam relative, Dioscorea bulbifera is very low maintenance; I pretty much just plant them under or near a tree I don't mind having covered by the vine, weed them once or twice or maybe thrice, and pee on them now and then. The yield can be excellent. Last April (or May?), I planted three moderately sized tubers, roughly the size of the three at far right in the photo. The harvest from those three plants is collected on the table (not counting any I failed to find; I didn't follow my advice above about having clear ground for easy harvest!) So in their first year, the plantings gave back roughly thirteen-fold, and hopefully now that the perennial roots have established, they'll yield even more this year.

Stored air potatoes beginning to sprout
Planting is from any of the tubers you harvested in the previous months; the larger the propagule, the more vigorously the vine takes off. I've found that the harvested aerial tubers sprout as much as two months earlier in storage than the roots remaining in the ground.

Toensmeir writes that you can cut a tuber into smaller pieces to plant out individually, so I cut three large tubers in half to double my planting stock. While the halves which got the existing sprouts continued to grow quickly, it took the other halves 6-8 weeks to develop new sprouts, so it may be best to perform this surgery well in advance of spring.

You could also make the cuts to eat most of the tuber while planting just the portion with the sprout.

A land owner where I lived has seen pigs eating both aerial and belowground tubers, but nonetheless, many plants survive from year to year. If pigs are a threat on your land, keep an eye out. Be prepared to gather fallen tubers frequently during harvest season, or to harvest them before they fall.

Hawaiians introduced both a bitter form of air potato, and Dioscorea pentaphylla. Both grow wild but are only eaten as famine food.

If you're curious for more, check out Spencer's air potato write up at Tropical Self Sufficiency.

No comments: