bulb ring suppresses turfgrass competition at the stem
Mechanism: Resource competition and physical occupancy of the root collar zone.
Evidence: settled without a trial - competition.
Currant Guild
A perennial guild - a standing planting, not lifted between seasons.
The fruit-tree guild's ring pattern, scaled to a berry shrub.
What binds this planting
The corpus backs this planting with 3 graded mechanisms its members share:
- Insectary plants near fruiting crops increase pollinator and predator visitation.
- Narcissus deters voles and rodents.
- A bulb ring suppresses turfgrass competition at the base of a woody perennial shrub or vine.
Space it needs
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.
What it looks like planted
- 1 × currant
- 8 × daffodil
- 1 × russian comfrey
- 8 × white clover
- 3 × yarrow
Between seasons
The guild is the standing planting; it is not lifted at all.
What it claims
understory insectary improves predator presence
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.)
chop-and-drop mulch cycles K and builds soil organic matter
fixer feeds the shrub in-season
Evidence: confirmed against 3 sources in the research-based literature.
the 3 sources
Univ. of Arkansas Extension, 'Creating a Three Sisters Garden', uaex.uada.edu (read 2026-07-11): 'Most of the nitrogen converted by the beans will not be available to the corn and pumpkins the first year; the bean roots have to break down to release nitrogen. Corn is a heavy nitrogen [feeder].'
Hupe et al. 2021, Sci Rep 11:11424, 'Evidence of considerable C and N transfer from peas to cereals via direct root contact but not via mycorrhiza', pmc.ncbi.nlm.nih.gov/articles/PMC8169652 (read 2026-07-11): reports 'a mean N transfer rate of 8.4%, with a range of 2.7 to 22.5%, ... from N2-fixing legumes to non-N2-fixing mycorrhizal cereals' and 'N transfer rates of between 3.1 and 6.0% ... from soybean to maize'.
'Nitrogen uptake and transfer in a soybean/maize intercropping system in the karst region of southwest China', pmc.ncbi.nlm.nih.gov/articles/PMC5648690 (read 2026-07-11): 'N transferred from soybean to maize account for 2.4%–3.3% of the N uptake of maize.'
The honest version
Currants and gooseberries tolerate part shade and take the fruit-tree guild's companion ring at berry scale. Ribes hosts white pine blister rust — the planner flags this automatically; where the disease is regulated, black currant may be restricted, so check before planting.
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.
Canopy
- Canonical: Currant
Fixer
- Canonical: White Clover
- Alternatives: Wild Lupine
Mulch producer
- Canonical: Russian Comfrey
Bulb ring
Insectary
- Canonical: Yarrow
- Alternatives: Dill, Lacy Phacelia, Borage, Lemon Balm, Chives
Rules that gate it
Perennial woody guilds are not bed-scoped. Their ground entity is the drip-line ring.
Mechanism: A tree's root zone expands for a decade and extends well past the canopy edge.
Evidence: settled without a trial - root architecture.
Do not plant a juglone-sensitive species within the root zone of Juglans. The sensitive list is the hazard's own, and it is wider than the nightshades - it also carries apple and cabbage.
Mechanism: Juglans roots exude hydrojuglone, oxidized to juglone, a respiration inhibitor. nightshades are highly sensitive: wilt and death.
Evidence: confirmed against 2 sources in the research-based literature.
the 2 sources
UW-Madison / Wisconsin Horticulture (Joy, Hudelson & Jull, rev. 2024-02-28), 'Black Walnut Toxicity', hort.extension.wisc.edu/articles/black-walnut-toxicity (read 2026-07-13): 'Vegetables such as tomato, potato, eggplant and pepper ... are particularly sensitive to juglone'; 'The toxic effects of a mature black walnut tree can extend 50 to 80 feet from the trunk of the tree, with the greatest toxicity occurring within the tree's dripline.'
Iowa State Univ. Extension & Outreach, Yard and Garden FAQ, 'What plants are sensitive to the juglone produced by black walnuts?', yardandgarden.extension.iastate.edu (read 2026-07-13): juglone-sensitive plants include 'members of the tomato family (tomato, potato, eggplant, pepper).'
remedy
Plant it outside the walnut's root zone — the whole drip line and beyond. There is no soil treatment for juglone.
Self-incompatible species require 2+ genetically distinct plants.
Mechanism: Many fruit trees carry self-incompatibility alleles at a single locus: when a pollen grain shares an allele with the pistil it lands on, the pistil rejects it and no seed sets. A plant's own pollen always shares its alleles, so it cannot fertilize itself — and neither can a second tree of the identical variety, which is genetically the same. Fertilization needs pollen from a genetically distinct plant.
Evidence: confirmed against 2 sources in the research-based literature.
the 2 sources
Penn State Extension, 'Pollination Requirements for Various Fruits and Nuts', extension.psu.edu/pollination-requirements-for-various-fruits-and-nuts (read 2026-07-11): 'Apple: Cross-pollination is always needed to produce adequate fruit crop'; 'Cherry: Sweet: Most varieties are self-unfruitful'; 'Those fruits listed as self-fertile will set fruit with their own pollen.'
'Pollen-Pistil Interaction in Response to Pollination Variants in Subtropical Japanese Plum (Prunus salicina Lindl.) Varieties', PMC9692414, pmc.ncbi.nlm.nih.gov/articles/PMC9692414 (read 2026-07-11): 'Japanese plum exhibits gametophytic self-incompatibility (GSI), a prezygotic reproductive barrier where genetically related pollen is rejected by the pistil ... governed by a polymorphic locus (S) ... Self-incompatibility occurs when the same S-allele is expressed in the haploid pollen grain and the diploid pistil.'
remedy
Plant at least two, and where the species needs a second cultivar make them different varieties — two of the same will not pollinate each other.