Tuesday, June 21, 2011

Perennial polyculture: New Designs

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

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


Following the massive failure of our original polyculture designs (see part one), I spent some time this past winter utilizing my hard-won knowledge of our successful perennials to try again. I didn't design anything for greens, since we have more than enough already established and coexisting quite nicely. I focused instead on root crops, which have proved more difficult to just plant here and there for a few reasons (not all reasons apply to all root crops):
  • Soil disturbance damages adjacent perennials or roots of woody plants
  • I lose track of where I planted odd plants after they've gone dormant, so can't harvest the roots
  • Roots (especially those starting from small tubers or seeds) get outcompeted by other perennials
In this post I'll present the polycultures we're trying this year. I'll also mention a few other ideas I've had but haven't tried to implement. Refer to part two of this series, species profiles, for individual plant characteristics, presented in roughly the same order in which they appear in polycultures in this post.



Garlic & Skirret

Garlic & skirret in foreground
volunteer burdock & more skirret in background
This bicrop makes use of different time niches with these two root crops. I planted garlic at about 9" between bulbs, with skirret between with 9" spacing to other skirrets and 4.5" to neighboring garlics. Garlic grows through the winter and has died down in early summer by the time skirret has gotten big enough to begin competing for light. Garlic bulbs should lift out easily without disturbing the skirret, and skirret's drought tolerance allows for non-irrigation of the garlic while the bulbs dry down.

This patch could be replanted in the same place year after year by harvesting all the skirret in September and October, then replanting garlic cloves and skirret crowns. Or move the garlic to a new patch and harvest the skirret as needed through the winter, replanting the skirret crowns into that new patch as they become available.

Skirret, Day Neutral Strawberry, & Oniony Thing

This patch combines the need to thin strawberry plants with the need to thoroughly dig up skirret roots. It works because you can leave skirret in the ground for two years before harvesting, and because we have day neutral strawberries which should be thinned in late fall or over the winter. (June bearing strawberries should be thinned after they bear their crop in mid summer). I planted four rows 15" apart in a 5' bed, with skirret and strawberries alternating in their rows every 8". (16" between strawberries, 16" between skirrets, 8" from a skirret to the closest strawberry.)

I planted some sort of evergreen oniony thing between the rows to have some winter growth of its edible leaves. Originally I planned for the ongoing disturbance of the skirret & strawberries to prevent the oniony thing from getting swamped out. But as of mid June, the oniony thing is dominating the area and I'm aggressively harvesting their leaves to open up space for the strawberry and skirret!

This fall I would harvest skirret from two of the four rows (rows 1 and 3), replanting skirret crown divisions after harvest. This will wipe out most or all of the strawberries in those two rows. Next year the strawberries left in the undisturbed rows 2 and 4 will recolonize rows 1 and 3, while the skirrets in rows 2 and 4 grow for a second year.

Next fall I would harvest the skirret in rows 2 and 4, wiping out those strawberries and replanting the skirret crowns. Then follow the same pattern in the future, harvesting two rows each year, such that each row is harvested every other year. This should keep the strawberries from crowding themselves out, as a natural byproduct of thoroughly digging the soil to harvest the skirret. I would adjust the size of the skirret crown divisions in future years to integrate well with the strawberry growth rate--smaller if the skirret is outcompeting the strawberries, or larger if the skirret is getting swamped.

Skirret, Oca, & Potato

This patch uses time niches to some effect, though it doesn't have any winter evergreens.

Oca and potatoes alternate in rows with 16" from one oca to the next potato, (32" from oca to oca and 32" from potato to potato.) I spaced two rows 30" apart in a 5' bed. I then planted one row of skirret halfway between the oca/potato rows, with skirret on 12" spacing within its row.

Skirret and potatoes grow vigorously early in the season, with oca putting on growth more slowly. We'll harvest potatoes July through September, with skirret still providing shade for the oca in the heat of the summer. With the cooler cloudier weather in September, the oca vegetation should quickly fill out to use up the space left behind by the potatoes. We'll dig all the oca tubers out after the first frost, and harvest skirret as needed through the winter. We can either reimplement the same polyculture in the same bed, or rotate it to other beds to prevent disease problems with the potatoes.

Oca, Asiatic Lily, & Yellow Asphodel

Confusing mess w/unplanned strawberry etc

Utilizes different time and height niches. These are planted in an understory wedge to the north of a young persimmon. At 6' tall the persimmon casts minor shade. Oca is planted on 30" centers with asphodel surrounding it on 10" centers. One lily is planted in the center of each oca "triangle". I don't have enough asphodel propagated yet, but eventually their density could be increased to about 6" between plants.

Asphodel grows from fall through winter til early summer, making its roots available for harvest while the oca is still small. The oca and asphodel provide ground cover for the lily, which grows above them. Harvest all oca after first frost, and harvest lilies as needed through the winter.

Lilies and asphodels can be harvested with fairly minor soil disturbance, so the main conflict might be the effects of oca harvest on the asphodel roots with their new-ish growth going into winter.

We planted this polyculture into an area somewhat invaded by strawberries, and with remnant camassia and weeds including dandelion & popweed. We may have trouble with the strawberries especially, since we don't have a strong ground cover or weed excluding element.

Yellow Asphodel, Good King Henry, & Violet

Utilizes height & time niches. Violet should be an evergreen (we're using Viola odorata) for permanent low ground cover and winter greens, with the yellow asphodel and good king henry (GKH) growing up through it. The GKH begins growing late in the spring, but the other two plants should help suppress early weeds, and the asphodel will then die down in summer for the GKH to fill out further. We should be able to harvest the asphodel roots in the summer with minimal disturbance to the GKH.

I planted GKH about 2' apart, and would eventually like to have asphodel at 6-8" spacing filling all the interior area. We don't have enough asphodel plants yet for full density, so they're more sporadic for now. The violets will fill in wherever they find gaps.

Jerusalem Artichoke, Mashua or Groundnut, & Chinese Artichoke or Creeping Bellflower

Jerusalem artichokes with small
chinese artichoke underneath
This polyculture has a core structure but multiple possible plants to plug into the different niches. It mimics the well known three sisters guild of corn, beans and squash, which Eric Toensmeier has proposed morphing into the perennial guild of jerusalem artichoke, groundnut, and chinese artichoke. This polyculture makes use of above ground space niches, but not of time niches, since these root crops require heavy disturbance for harvest in fall through early spring. With the possible exception of the creeping bellflower, they should all benefit from the regular ground disturbance and loosening of the soil.

We're retaining jerusalem artichoke as the vertical element; we had an existing 100 square foot patch. However, we've never had much success growing ground nuts here, so we only planted 3 or 4 which survived from last year, instead mostly planting mashua on 3' centers as the vining element to climb the jerusalem artichokes. We can easily supply nitrogen via our urine so we don't require the leguminous groundnut for nitrogen fixation.

For the ground cover layer, we're trying about half a dozen fast-spreading chinese artichoke in half the patch, with creeping bellflower 1-2' apart as another vigorous, shade tolerant root crop in the rest of the area.

Our patch gave us about 100 pounds of jerusalem artichokes last year (1 pound per square foot). It makes sense to knock back the jerusalem artichoke production a bit in favor of more root diversity, and hopefully the total yield of roots will increase while we're at it.

Brief Mention

Oca & Tomatillo / Ground Cherry

Ocas & tomatillo at bottom
tree collard and mashua at top not part of guild

Inspired by oca-testbed's oca & tomato bi-crops, I've planted 3 ocas, 2 annual ground cherries, and 2 tomatillos with 10" between each oca and its neighboring ground cherry or tomatillo (20" from one ground cherry or tomatillo to the next).

Squash & yacon

I planted some squash seeds at 6' centers and yacon halfway between at the 3' mark. The yacon should grow tall enough to hold its own by the time the squash reaches it, to share the space niche a bit. It may work somewhat as a time niche, too, as squash often dies back in early to mid fall with powdery mildew, while the yacon can keep growing until frosts kill it.

Not Implementing

Oca & squash

We created an accidental time niche bicrop a few years ago when a squash covered up some oca for most of the summer, but started dying back with powdery mildew in early fall, allowing the oca to explode in growth and fill out the space. We didn't get much of an oca yield--but I wasn't experienced enough at that time to pay close attention to frost and harvesting all the oca promptly. So maybe we got some roots but they rotted? Or maybe the squash didn't allow the oca to grow well enough to produce roots? I'd like to try this again with squash on 6' centers and two or three ocas at the 3' point in between. Or try combining it with the squash & yacon polyculture, with the squash and yacons spaced further apart to allow oca some breathing room between the larger plants. (See oca-testbed's polyculture mound of yacon, oca, and chinese artichoke.)

June bearing strawberry & summer root crop

I've tried to design a polyculture which combines digging some root crop with the need to thin June bearing strawberries in late summer, after they've finished cropping for the year. I've had a much harder time with this than with day neutral strawberries (see my polyculture with skirret above), since very few root crops can be harvested in the summertime after two years of growth to allow the alternating row harvest method. Strawberries fill out quite well by mid spring, creating a lot of competition for anything shorter than they are, limiting the ability to sow seeds or plant small divisions at the beginning of the growing season. Further, the root crop can't be allowed to outcompete the strawberries too badly -- we have some burdock in our patch, and we have to keep harvesting the huge leaves (we do eat the leaf stalks) or the strawberries get totally covered up!

Spring ephemeral bulbs such as Camassia, Triteleia, Brodiaea, or Erythronium might work for the row harvest method, especially if you establish a solid patch first, then add strawberries later. Or instead of harvesting a full row at at time, you could do a distributed harvest of the thickest clumps of bulbs, disturbing patches of strawberries here and there while eating the largest ephemeral bulbs and leaving the small ones behind to regrow quickly the following spring. Or try root crops whose seeds can germinate in the autumn, overwinter as a small plant, and grow quickly in spring: black salsify (Scorzonera hispanica) or dandelions for full row harvest after 1.5 years, or black salsify, dandelions, or parsnips for distributed patch harvest the summer after they've been sown.

1 comment:

Unknown said...

Hi Norris. Interesting, inspiring and well-considered stuff. Let's hope the plants stick to the plan :-)
The Skirret/Oca/Potato arrangement caught my eye. I'd pretty much decided that potatoes are best in a monoculture, but you have made me reassess. Variety of potato would be critical though: there is such a variance in maturity time and ultimate spread.
My experience of Jerusalem artichoke showed that it has limited potential for polycultures in my climate. It sucks all moisture out of the soil to the detriment of anything else growing amongst it. But in a wetter climate, or with irrigation it has a lot of possibilities.
I look forward to seeing how it all goes.