A polyculture - the species are claimed to help each other, and each claim below names its mechanism.
Contested and regional. The fourth sister is variously given as sunflower, Rocky Mountain bee plant, or amaranth, depending on nation and source. Do not present a canonical version.
What binds this planting
The corpus backs this planting with 3 graded mechanisms its members share:
At least 4 m²43.1 ft². A bed smaller than that does not get this guild quietly substituted for something else — the planner greys it out, says why, and offers the nearest adaptation that does fit.
The real placement, on an example 10 ft bed - the same layout the planner draws.
Between seasons
Nothing is left living in the bed over winter; the whole planting is re-established.
What it claims
insectary draws pollinators and predatory insects
A good hunch
Mechanism: The flowers supply nectar and pollen that adult predators and parasitoids feed on, so a patch of them near a fruiting crop keeps those beneficial insects fed and close by to work the crop. The effect is real but not guaranteed — an insectary patch does not always suppress pests.
Evidence: confirmed against 1 source in the research-based literature.
the source
UC Statewide IPM Program (UC IPM), 'Insectary Plants', ipm.ucanr.edu/environmental-protection-and-pesticide-stewardship/insectary-plants (read 2026-07-11): 'Insectary plants are those grown to attract, feed, and shelter insect parasites (parasitoids) and predators to enhance biological pest control. Insectary plants provide nectar and pollen, which the adults of many natural enemy species need to consume.' (UC IPM also notes 'insectary plants may not always help' suppress pests — consistent with the 'reasonably supported' framing.)
Roles
A role is filled by whatever satisfies its predicate, not by a fixed species list. The canonical filler is the default; the alternatives are priced.
What the alternative costs: A sunflower feeds natural enemies from its extrafloral nectaries as well as from its flowers, and it pays for that twice here: it is a heavy nitrogen feeder set among corn that is already one, and it casts shade over the mounds the squash and beans are working. Borage carries neither cost - it stays short and casts none.
What it costs the ground
Rotation history attaches to the ground, not the bed, so this is what the planner remembers about this patch after the guild comes out.
Grasses: full load
Legumes: full load
Cucurbits: full load
Rules that gate it
Well established
Corn requires a block of at least 4 rows (roughly 12 plants) for adequate kernel set.
fatal if ignored → block
Mechanism: Maize is wind-pollinated and protandrous. Tassels shed pollen that must land on silks of neighbouring plants. Below roughly 12 plants in a block of at least 4 rows, insufficient pollen reaches enough silks; each unfertilized silk is one missing kernel.
Evidence: confirmed against 4 sources in the research-based literature.
the 4 sources
UMN Extension, 'Growing sweet corn in home gardens', extension.umn.edu/vegetables/growing-sweet-corn (read 2026-07-11): 'Always plant corn in blocks of at least four rows. Corn planted in a single row will have much of its pollen blown out of the row, and will produce ears that have blank areas where kernels did not form.'
NC State Extension, 'Organic Sweet Corn Production' (Horticulture Information Leaflets), content.ces.ncsu.edu/organic-sweet-corn-production (read 2026-07-11): 'Corn is wind-pollinated and should be planted in blocks of at least 4 rows for good pollination to occur.'
UMD Extension, 'Growing Sweet Corn in a Home Garden', extension.umd.edu/resource/growing-sweet-corn-home-garden (read 2026-07-11): 'Plant in blocks of at least three to four short rows, rather than one or two long rows, to ensure good pollination; minimum of three rows side by side (preferably four rows).'
Clemson HGIC 1308, 'Sweet Corn' (updated 2023-01-23), hgic.clemson.edu/factsheet/sweet-corn (read 2026-07-11): 'This crop is wind-pollinated; therefore, plant in blocks of several rows rather than 1 or 2 long rows to ensure full ears.'
remedy
Plant in a block of at least 4 rows, or omit corn and substitute a trellis.
