Monday, June 06, 2011

Perennial polyculture species profiles

This is part two of a three part series on perennial polycultures:

  1. Designs: a five year review
  2. Species profiles
  3. New designs


In Perennial polyculture designs, I mentioned inadequate knowledge of plants as one barrier to successful implementation of my designs. We've now gained enough knowledge of a few perennial plants to try again. With this mouthful of a title, I give the relevant design characteristics of perennial vegetables we're trying in polycultures this year. Unless otherwise noted, I consider these plants primarily root crops, though some have secondary uses like edible flowers or leaves. By the way, for more information on many of these unusual root crops, including some polyculture experiments, see:
  • Oca testbed - nice details on tomato & oca bicrops, plus lots more on oca and some on other roots
  • Radix Root Crop Research and Ruminations - pioneering work with many roots I haven't tracked down or in some cases even heard of before
  • Obligatory link to Plants for a Future database.

Species characteristics

Garlic (Allium sativum)

  • Harvest time: July or August
  • Harvest process: Lift all bulbs, which doesn't require much soil disturbance. Store in cool dark place.
  • Planting process: Plant cloves in October or November, which doesn't disturb soil, but cloves shouldn't be disturbed by other digging after being planted.
  • Generally doesn't require any watering, and in fact shouldn't receive water in July so the bulbs can dry out for long term storage.
  • Vegetative growth: small amount of leaves over the winter, growing more actively in spring. Die back in July with the summer drought.

Skirret (Sium sisarum)

  • Harvest time: October through April. Stores in the ground all winter.
  • Harvest year: can harvest after one year of growth, or leave in the ground for multiple years for more and larger roots, which seem less prone to having a woody core.
  • Harvest process: Dig large chunk of soil from around plant (up to 2.5' diameter with older plants), pull out crown. Cut off roots, optionally divide and replant crown. Can be difficult to find in late winter after stalks have rotted away.
  • Drought & shade tolerant
  • Vegetative growth: Appears mid-season (April), grows fairly quickly to 3-5' tall (depending on age of plant), and dies down in early fall (October). Dense, casting heavy shade.

Garden strawberry (Fragaria x ananassa)

  • Use: berries
  • Harvest time: summer through fall
  • Best with full sun and adequate water through growing season.
  • Benefits from thinning (following the annual harvest for June bearing varieties, and in the winter for day neutral varieties)
  • Vegetative growth: semi evergreen to 1' high, spreading quickly from runners

Potato (Solanum tuberosum)

We haven't actually grown potatoes very much, but my understanding so far:
  • Harvest time: June onwards. Can probably store in the ground through the winter?
  • Harvest process: Seems to need a fairly thorough excavation of the soil, especially to find all the roots. We had many potatoes return this year from last year's plantings, so this seems to have potential as an overwintering perennial. Disease buildup normally demands crop rotation.
  • Supposedly fairly drought and shade tolerant.
  • Vegetative growth: Starts growing in late March or April. Reaches 3' wide? Yields supposed to improve with hilling up soil onto the lower stem.

Oca (Oxalis tuberosa)

  • Harvest time: after the first light frost(s) kill the foliage, but before hard freezes damage the tubers, which often dwell close to the soil surface.
  • Harvest process: Dig out all the roots, generally concentrated at the center, though some may form where foliage touches the soil. Store in cool dark place for the winter, replanting some tubers in spring. In mild climates, tubers missed at harvest time may resprout on their own in spring.
  • Appreciates some shade during heat of the summer, but may not tolerate too heavy competition. We tried it as a ground cover amongst other plants one year, and they swamped it out with very little root yield.
  • Vegetative growth: Leafs out in April or May, generally low growing to about 1', though can clamber up other plants if it needs to gain access to sunlight. Doesn't put on much growth until September, when cooler cloudier weather kicks in, at which time the foliage explodes to 3-4' wide.

Asiatic lily (Lilum sp)

  • Harvest time: Late fall through early spring.
  • Harvest method: Compact bulb, so fairly easy to harvest with minimal soil disturbance. Leave large offsets behind to regrow. Can be difficult to find in late winter after top stalks have rotted away.
  • Like their feet in shade and top growth in sun, thus well suited to combination with a low ground cover.
  • Vegetative growth: comes up in early to mid spring, grows to 3-4' tall, and dies down in fall.

Yellow asphodel (Asphodeline lutea)

  • Harvest time: Can definitely harvest in the summer, and I think we can dig roots year round.
  • Harvest process: Medium soil disturbance, concentrated around center of each plant. The plants make numerous offsets, and each plant has multiple thin roots. So you can harvest some entire plants and leave/replant others, or cut some of the roots off of each plant and replant them all for slower/less vigorous regrowth. Not sure yet of the best method.
  • I think it prefers full sun, and probably doesn't need any irrigation.
  • Vegetative growth: somewhat sparse, to about 1.5' tall on flowerless plants, or 3' tall on single flower spike. Doesn't seem to compete all that well with other plants, so may do best with a low growing ground cover for weed exclusion. From the Mediterranean, so well adapted to our summer drought by dying down in mid summer and coming back with fall rains, staying green through the winter.

Good King Henry (Chenopodium bonus-henricus)

  • Uses: leaf crop (spinach substitute) and seed crop (used like quinoa, though smaller).
  • Harvest time: leaves throughout season. Seeds over a period of about three months, July through September.
  • Harvest process: seeds require periodic picking every week or two as different seed stalks ripen at different times.
  • Somewhat shade & drought tolerant, though I assume for optimum seed production we should give it full sun and summer water.
  • Vegetative growth: comes up in late spring, reaching about 1.5' tall and perhaps a bit wider. In our back yard where chickens roam, we have a fairly pure stand of GKH and it does fine. In our front yard, (because chickens aren't eliminating the other plants? or because the GKH hasn't dominated the root zone yet?) the GKH gets crowded out by the early spring growth of nipplewort (Lapsana communis), lemon balm (Melissa officinalis), and wood avens (Geum urbanum) and I've had to weed the bed this year. Like the yellow asphodel, would probably benefit from a low growing weed suppressing ground cover.

Jerusalem artichoke / Sunchoke (Helianthus tuberosus)

  • Harvest time: October through April
  • Harvest process: Major soil disturbance. Will always miss some roots so that it will regrow the next year. Can be difficult to find roots in late winter after stalks have rotted.
  • Drought and shade tolerant
  • Vegetative growth: appears mid spring, reaches 8+' tall. Dies off in late fall.

Mashua (Tropaeolum tuberosum)

  • Harvest time: In theory, should harvest after the first light frost(s) kill the foliage, but before hard freezes damage the tubers. Roots seem much hardier than oca and yacon, though, such that they might store OK in the ground through the winter.
  • Harvest process: Fairly thorough excavation to dig all roots, storing in cool dark place for the winter. We usually miss some of the roots so that it regrows the next year.
  • Appreciates some shade during heat of the summer
  • Vegetative growth: Vining to at least 10' tall, climbing other vegetation. Appears in mid spring and grows at a fairly steady rate until frosts.

Groundnut (Apios americana)

(c) 2004 Steve Baskauf
We haven't had much success with this plant, but we haven't totally given up on it yet..
  • Harvest time: dormant season, late fall? through late spring?
  • Harvest method: Extensive excavation required. Leave some tubers behind to regrow.
  • Fixes nitrogen
  • Vegetative growth: vining, scrambling up surrounding vegetation. In our climate, appears around June and disappears in September or October.

Chinese artichoke (Stachys affinis)

We've only grown these for one year, so I base this mostly on the literature:
  • Harvest time: Dormant season (fall through early spring)
  • Harvest process: Probably requires major soil disturbance, especially since I don't think dead plants leave woody stalks behind to mark their spots. Will regrow in spring from tubers you missed.
  • Moderate moisture requirements?
  • Vegetative growth: appears in early or mid spring, gets about 1' to 1.5' tall, runs quickly (mint family) and forms good ground cover. Not sure exactly when it dies down.

Creeping bellflower (Campanula rapunculoides)

  • Harvest time: I think we can get usable roots year round.
  • Harvest process: Fairly major soil disturbance. Need to dig towards the center of the clump to find usable roots. I suspect it will keep regrowing vigorously after each harvest with no need to deliberately leave roots behind.
  • Very shade tolerant, and competes well with other vegetation.
  • Vegetative growth: Leaves appear in early spring and make a good source of greens while others are somewhat scarce. Plant reaches about 3' tall and runs vigorously. I think that without irrigation it responds to our summer drought by going somewhat dormant, resuming growth in the fall before dying back for good over the winter.

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