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// SPECIES PROFILE · PERENNIAL · INTRODUCED · PERMACULTURE STAPLE

Comfrey

Symphytum officinale · Symphytum × uplandicum (Bocking 14)

The deep-taprooted, fast-growing, perennial herb that anchors most permaculture orchard plantings — harvested four or five times a season for high-mineral mulch, brewed for nutrient-rich foliar tea, and worked by bumblebees, hummingbirds, and the carpenter bees that rob nectar through the side of its tubular flowers. Symphytum officinale is the European wild species; the most-recommended cultivar for NE Oklahoma food-forest design is the sterile triploid hybrid 'Bocking 14' — productive, non-spreading by seed, and root-cutting propagated.

// QUICK FACTS
Family
Boraginaceae (borage family)
Group
Perennial — long-lived herbaceous clump-former
Native range
Europe and W Asia; introduced to N America in colonial era
USDA hardiness
Zones 3–9 (Tulsa = 7a/7b)
Mature size
2–4 ft tall × 2–4 ft wide
Sun
Full sun to part shade
Soil
Tolerates almost anything; thrives in rich moist soil
Water
Average; deep taproot makes it drought-resilient
Bloom
May–Sept; pendant pink-purple-cream tubular flowers in scorpioid cymes
Root depth
3–10 ft taproot — the source of its “dynamic accumulator” reputation
Cuttings
4–5 per growing season; regrows from cut crown in 4–6 weeks
Wildlife value
Bumblebees, mason bees, hummingbirds; nectar-robbed by carpenter bees
Toxicity
Pyrrolizidine alkaloids — not for internal medicinal use
Ecological role
Biodynamic accumulator · pollinator · permaculture staple
Comfrey (Symphytum officinale) — broad hairy leaves and pendant pink-purple flowers
Symphytum officinale — broad hairy basal leaves and pendant scorpioid cymes of tubular pink-purple flowers. Photo via Wikipedia / Wikimedia Commons.

Identification

[ field key — leaves · flowers · roots · cultivars ]

Habit & leaves

Stout herbaceous perennial 2–4 ft tall, growing as a single or clumped rosette of large basal leaves with smaller leaves up the flowering stems. Leaves are alternate, simple, broadly lanceolate to ovate, 8–18" long on basal rosettes, with prominent coarsely bristled and roughly hairy upper surfaces. The hairs are silica-loaded and irritating to bare skin (a useful ID feature). Stems are winged where the leaf base extends down (a key Symphytum trait).

Flowers

Borne in scorpioid cymes — one-sided coiled clusters that uncoil as flowers open in sequence — from the tip of upright leafy stems. Individual flowers are pendant, tubular- bell-shaped, ~1/2–3/4" long, with five fused petals and color that ranges from creamy yellow-white in S. officinale to pink-purple in S. asperum and the hybrid S. × uplandicum. Bloom continues from May through September on healthy plants.

Roots — deep & black

The single most consequential feature: a stout, fleshy black-skinned taproot branching deeply — mature plants commonly send roots 3–10 ft into subsoil, drawing up minerals (potassium, calcium, phosphorus) from below the reach of most garden plants. The roots are also the source of comfrey's propagation challenge: any root fragment left in the ground will regenerate a new plant.

The 'Bocking 14' hybrid

Most permaculture-recommended comfrey is the cultivar 'Bocking 14', a sterile triploid Symphytum × uplandicum selected by Lawrence D. Hills in the 1950s at the Henry Doubleday Research Association (Bocking, Essex). Its sterility is critical: it cannot escape by seed, sets no viable achenes, and spreads only by deliberate root-cutting propagation. True wild S. officinale, by contrast, can self-seed aggressively in moist garden settings.

Habitat & Range in NE Oklahoma

Comfrey is not native to North America. Symphytum officinale is a Eurasian wetland-edge plant of damp meadows, streambanks, and ditches, introduced to the eastern United States in the colonial period as a medicinal herb and persisting locally around old farmsteads, herb gardens, and Pennsylvania-Dutch homesteads. It is naturalized in scattered locations across the eastern US but does not form extensive wild populations in NE Oklahoma — soils here are typically drier and more alkaline than the species prefers, and summer heat suppresses late-season growth.

In the Tulsa region, you will encounter comfrey almost exclusively in cultivated settings: permaculture orchard understories, urban food-forest plantings, biodynamic and herb gardens, and around the edges of vegetable gardens where it has been intentionally placed as a living fertility resource. It thrives in the moister soils of the Cross Timbers oak-hickory ravines, in the alluvial loams of the Verdigris and Caney bottoms, in irrigated raised beds, and along greywater-irrigated orchard guilds where its deep taproot can locate consistent subsurface moisture. It is much less successful on shallow chert ridges, on the rocky alkaline limestone of Osage County, and on unirrigated south-facing slopes.

Practically speaking: place comfrey deliberately where you want it, in a location with reasonable soil moisture and at least afternoon shade during August's worst heat. Once established, plants typically live for 20+ years without disturbance and increase only modestly in clump size from the original planting.

Ecology & Wildlife Value

[ pollinators · nutrient cycling · soil · toxicity ]

Pollinators

Comfrey flowers are designed for long-tongued bumblebees: pendant tubular corollas with nectar at the base. Bombus pensylvanicus, B. impatiens, B. griseocollis, mason bees, leafcutter bees, and hummingbirds work the flowers from the front (legitimate visitation). The flowers are also a favorite of large carpenter bees (Xylocopa virginica), which often nectar-rob by chewing a hole through the side of the corolla — smaller bees then visit the same perforation, bypassing pollination entirely. Watching the carpenter bee & honeybee dance around a comfrey clump in May is one of the quieter pleasures of the orchard understory.

The "dynamic accumulator" claim

Comfrey leaves analyze high in potassium (~5–7% on dry weight basis), calcium, nitrogen, magnesium, and several micronutrients — concentrations comparable to or exceeding most cover crops. The deep taproot is the source: it accesses subsoil mineral pools largely unavailable to shallow- rooted annual crops. Cut-and-mulch use of comfrey effectively pumps these subsoil minerals to the surface for use by neighboring fruit trees and vegetables. The "dynamic accumulator" framing is sometimes overstated in permaculture literature but the measurable nutrient mobilization is real.

Soil & mycorrhizae

Comfrey is a non-mycorrhizal plant — its roots rely on bacterial associations and on the brute force of deep taproot exploration rather than the fungal symbiosis that most garden plants use. Practically this means comfrey will establish in poor or compacted soils where mycorrhizal partners are sparse, and that the cut leaves return a different nutrient profile to the soil surface than (for example) cover-crop residue from clover or rye.

Pyrrolizidine alkaloid toxicity

All Symphytum species contain hepatotoxic pyrrolizidine alkaloids (PAs) — especially in roots, less so in mature leaves. PAs cause irreversible liver damage on chronic ingestion and are listed by the FDA as unsafe for internal consumption. Topical use on intact skin appears safe; internal medicinal use is no longer recommended despite the plant's long European medicinal history.

Wild seed-spreading vs. sterile cultivar: Wild Symphytum officinale is a vigorous self-seeder in moist gardens and can become difficult to remove (any root fragment regrows). For permaculture and orchard use in NE Oklahoma, plant only the sterile triploid 'Bocking 14' or the closely related 'Bocking 4' — both are seed-sterile, propagated only by root division, and stay where you put them. Sources include Coppertop Farm, Strictly Medicinal, and Horizon Herbs.
Internal-use warning: Despite folk-medicine traditions naming comfrey "knitbone," the FDA, the German Commission E, and the UK Medicines and Healthcare products Regulatory Agency all advise against internal consumption due to documented liver toxicity from pyrrolizidine alkaloids. Topical use on unbroken skin is generally considered acceptable in short courses; do not consume comfrey tea, capsules, or fresh leaves internally.

Horticulture & Care

[ siting · root cuttings · cutting-and-mulch · tea ]

When to plant intentionally

Plant comfrey deliberately as a permanent fertility hedge: in the drip line of a fruit tree to capture leaf litter and recycle subsoil minerals, around the base of a chicken yard to absorb manure nitrogen, along the downhill edge of a vegetable garden to intercept leached nutrients, or as a perimeter plant on contour swales in food- forest design. Do not plant in mixed perennial borders where its bristly foliage is unattractive at close range, in narrow turfgrass beds (impossible to remove later), or near aggressive grass species that will compete heavily with newly established plants.

Planting from root cuttings

Cut-and-mulch management (the core practice)

The fundamental management approach is to cut the entire above-ground portion 4–5 times per growing season — roughly once every 5–6 weeks from May through September — and use the cut foliage as in-place mulch around fruit trees, vegetables, and other heavy feeders. Each cut pulls a fresh batch of subsoil minerals to the surface; the cut crown regrows in 4–6 weeks. Wear gloves (the bristles are irritating) and use sharp shears or a sickle. Cut just above the crown but not into it.

Comfrey tea (concentrated liquid fertilizer)

For a concentrated liquid fertilizer, fill a lidded 5-gallon bucket roughly 3/4 full of fresh-cut comfrey leaves (no water), cover, and let sit for 3–6 weeks. The leaves break down anaerobically into a black, exceptionally smelly, mineral-rich liquid. Strain and dilute roughly 1:10 with water for use as a foliar feed or root drench. The smell is genuinely terrible — site the bucket far from the house and downwind.

Long-term management & removal

Comfrey clumps are essentially permanent: they outlive most of the people who plant them, expanding modestly in clump diameter over the decades but not aggressively spreading (especially with the sterile 'Bocking 14' cultivar). Removal, if needed, requires thorough digging out of the entire taproot system; any 1" root fragment left in soil will regenerate a new plant within a season. Repeated mowing eventually exhausts the crown but takes 2–3 years.

Pests & diseases

Cultural & Material Uses

Comfrey has been cultivated in European gardens since at least Roman times, originally as a medicinal herb (the genus name Symphytum comes from Greek symphyton, "to grow together," referring to its traditional use on broken bones). Modern uses have shifted decisively toward soil and garden fertility rather than internal medicine.

Sources & Further Reading

  • USDA NRCS PLANTS Database — Symphytum officinale: plants.usda.gov/plant-profile/SYOF
  • Lady Bird Johnson Wildflower Center — Symphytum officinale: wildflower.org — SYOF
  • Missouri Botanical Garden Plant Finder — Symphytum officinale and S. × uplandicum 'Bocking 14'.
  • Hills, L.D. (1976), Comfrey: Past, Present and Future, Faber & Faber — the foundational text on the cultivation and selection of 'Bocking 14'.
  • Toensmeier, E. (2007), Perennial Vegetables, Chelsea Green — comfrey in the context of permaculture perennial-food systems.
  • Garden Organic (UK; formerly Henry Doubleday Research Association) — comfrey research summaries and 'Bocking 14' propagation guidance.
  • FDA Center for Food Safety and Applied Nutrition — 2001 advisory on pyrrolizidine alkaloid toxicity in comfrey products.
  • Wikipedia — Symphytum officinale: en.wikipedia.org/wiki/Symphytum_officinale (CC BY-SA 4.0; portions of the description, ethnobotany, and toxicity sections summarize Wikipedia content).
  • Mader, E. et al. (Xerces Society) — Attracting Native Pollinators, Storey Publishing — comfrey as bumblebee forage.
  • Stickel, F. & Seitz, H.K. (2000), "The efficacy and safety of comfrey", Public Health Nutrition 3(4A): 501–508 — clinical review of PA-related liver toxicity.

Companion Planting

[ guild · polyculture · cross-layer pairings ]

In a multi-layered food-forest guild, comfrey pairs naturally with: american persimmon (Diospyros virginiana), american beautyberry (Callicarpa americana), maypop / passionflower (Passiflora incarnata), cosmos (Cosmos bipinnatus), common sunflower (Helianthus annuus), and black cherry (Prunus serotina).

Combine comfrey with the warm-season grasses listed above for a self-sustaining matrix.