The illustrated growing guide

Comfrey

Symphytum × uplandicum

Family Boraginaceae

Est. zones 4-9

Botanical illustration of Comfrey — Perennial · Symphytum × uplandicum

A sterile Russian-comfrey hybrid, so it sets no seed and never becomes the roadside weed common comfrey can. A deep-rooted dynamic accumulator: chop the leaves 3-4x a season for high-potassium 'comfrey tea' or chop-and-drop mulch under fruit trees. Increase it only by root cuttings or crown division, and site it for good — the roots make an established clump very hard to move.

Perennial

⚠ Spreads aggressivelyComfrey spreads vigorously and regrows from bits of root, so it's very hard to fully remove once established — give it a contained bed or a spot where it can roam freely, and edge it every year.

Where to buy the plant — 1 nursery

Comfrey — a print from the Medicinal Herbs collection

From the print shop

The closest print we make

We don’t print Symphytum × uplandicum. The closest we have is Symphytum officinale (“Comfrey”) in the Medicinal Herbs collection — the same genus, Symphytum, not the same species.

16 designsfrom $21.99white or black groundmatte poster, unframed

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Overview

Will comfrey suit your garden, and what goes wrong.

✓

Will it fruit where you are?

Enter your ZIP — we look up your USDA hardiness zone (2023 map) and check it against what comfrey actually needs.

Hardy inZones 4-9

Comfrey at a glance

HardinessUSDA 4–9

Mature size2-3 ft

PollinationAttracts pollinators, but plant is sterile (propagates by root division only).

Chill requirementNot yet established

Bloom seasonSpring/Summer

Harvest seasonCut 3-4 times/season

Growth rateVery Fast

Common comfrey problems

None specific
None specific

I·b

The Bocking strains

Why garden comfrey is sterile, and which number to plant.

Garden comfrey is Russian comfrey (Symphytum × uplandicum), a sterile hybrid — it sets no seed, so unlike common comfrey it can't sow itself into a roadside weed. You increase it only by root cuttings or crown division.

In the 1950s Lawrence D. Hills — who went on to found the organic-gardening HDRA — trialed 21 comfrey strains at Bocking, Essex and numbered them Bocking 1–21. Only two are still grown today, and they split by job:

Bocking 14 — the gardener's strain: the highest potassium (~7% potash), the best comfrey-rust resistance, and thin leaves that rot down fast. The champion for chop-and-drop mulch, compost, and “comfrey tea.”
Bocking 4 — the forage strain: deeper-rooted and more drought-hardy, higher in protein and lower in the alkaloids that make comfrey unsafe to eat — the pick if animals will graze it.
Plant it once, on purpose. The deep taproot that mines minerals also makes an established clump very hard to dig out — put it where you want it for good, under fruit trees.
Not for the kitchen. Comfrey's pyrrolizidine alkaloids are hepatotoxic; treat it as a topical and garden herb, never a regular edible.

Pick your strain in the cultivar catalogue below.

Growing

Light, water, soil, propagation and the season’s jobs.

How to grow comfrey: light, water & soil

LightFull Sun to Shade

WaterModerate

SoilAdaptable · pH 6.0 - 7.0

FertilizerHigh Nitrogen feeder (use urine or manure)

PruningThroughout season — Cut to ground for mulch ('Chop and Drop').

Spacing2-3 ft

How to plant & propagate comfrey

PropagateRoot cuttings or crown division only — sterile, sets no seed

The comfrey growing playbook

Field-tested instructions for every job comfrey asks of you, compiled from university extension guidance — in the order the season brings them.

Watering

Water when the top 2 inches go dry

Check the soil between cuttings and water once the top 2 inches are noticeably dry. Aim for moderate, steady moisture rather than letting the patch swing between soaked and bone dry. The roots run deep enough that comfrey rides out drought, but it still prefers moderate soil moisture, and the leafy regrowth you are asking for after each cut is mostly water.

Feeding

Feed nitrogen through the cutting season

Soil test before planting and work the fertilizer into the top 6 inches. On an established patch, apply roughly 1 to 2 teaspoons of 21-0-0 per square foot per month through the growing season. Comfrey is not a legume and cannot fix its own nitrogen, and you carry the entire leaf mass off the plant several times a year. Every cutting exports nitrogen the plant has to replace before it can push the next flush.

Dividing

Start new plants from root cuttings or crown divisions

Comfrey can go in any time from April to September, but it establishes best in spring. Lay root cuttings flat 2 to 4 inches deep, putting the longer pieces deeper, and set crown divisions or transplants upright about 2 inches deep. Space rows 2 to 3 feet apart in a checkerboard, tightening the spacing if you want more leaf per square foot. Comfrey rarely produces seed, so cuttings and divisions are the only practical way to increase it. Root cuttings take 3 to 6 weeks to push buds while crown divisions break ground in about 10 days, which is why divisions are the choice when you want leaf the same year.

What to watch for

Walk the edge of the patch and pull strays early

Each spring, look for shoots coming up outside the bed you planted, especially anywhere you dug or moved soil last year. Lift young strays whole while the root is still shallow. Control weeds in the patch by shallow cultivation only, and avoid damaging comfrey roots, which sets the plant back. Comfrey is propagated from root cuttings precisely because root pieces develop buds and grow on, so soil-moving work around a patch tends to spread it rather than remove it. Utah State Extension warns comfrey can become invasive if it is not contained or controlled, which is why it is worth checking the edges once a year while strays are still small.

Harvesting

Cut leaves every two weeks, 2 inches above the crown

Leave the plant alone the first year and start cutting in year two. Once established, gather a bunch of leaves and cut about 2 inches above the ground every 2 weeks through the growing season. If you want root as well, dig from one side of the root system only so the plant carries on. Cutting low and often keeps the crown pushing fresh leaf instead of running to flower, and the first season is what the plant needs to build the deep root that funds every later cut.

⚠ Comfrey contains pyrrolizidine alkaloids that can cause lethal liver toxicity if eaten repeatedly or in high doses. Do not treat these leaves as food or tea, and anyone with a known liver condition should talk to a doctor before ingesting comfrey in any form.

Comfrey companion plants

Good companions

Fruit trees (chop-and-drop mulch under them)

Underlined names have their own growing guide in this library.

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The year

What comfrey asks for, month by month.

The comfrey year, month by month

MonthJanFebMarAprMayJunJulAugSepOctNovDec

Bloom

Prune

Harvest

What each band means

Bloom — flowers open — pollinators working, frost on blossoms is the danger.
Prune — shape it now — cuts heal cleanly and structure is visible.
Harvest — picking time — check ripeness every few days.

The comfrey year as text

Jan pruning
Feb pruning
Mar bloom, pruning
Apr bloom, pruning
May bloom, pruning, harvest
Jun bloom, pruning, harvest
Jul bloom, pruning, harvest
Aug bloom, pruning, harvest
Sep pruning, harvest
Oct pruning
Nov pruning
Dec pruning

These are the species' typical months — expect them a few weeks earlier in warm zones and later in cold ones. Watch the plant, not just the calendar.

Ecology & uses

What it does for the garden, and what it is grown for.

Comfrey in the garden system

Herbaceous layer perennial
Dynamic accumulator
Nectary/insectary

AttractsBees

MoistureFacultative / average

SaltSalt-tolerant — fine near roads and coasts

DeerBrowsed — protect young plants

OriginIntroduced

What comfrey is grown for

! Some parts toxic — see notesNever take internally — pyrrolizidine alkaloids cause sinusoidal obstruction syndrome and severe liver injury (FDA asked manufacturers to remove oral comfrey supplements in 2001). Topical use only, on intact skin, in short courses (EMA: about 10 days; Germany caps 4-6 weeks a year). Avoid in pregnancy and breastfeeding, and use caution on children.

UseMulch

UseCompost Activator

Traditional useSalve (Medicinal)

Traditional use rating3/5 in herbal tradition

Harvesting & storing comfrey

Cut 3-4 times/season.

Edibility, identification, and traditional-use notes here are general reference — not medical or veterinary advice, and not a claim that any plant treats or prevents anything. Medicinal ratings record how strongly a plant features in herbal tradition, nothing more. Never eat or dose a plant you have not positively identified. More on how to use this library.

Cultivars

Named varieties of comfrey, ruled as a catalogue.

Best comfrey varieties & cultivars

2 on file

Comfrey's named strains are the Bocking series — sterile Russian comfrey (Symphytum × uplandicum) selections bred by Lawrence D. Hills at Bocking, Essex in the 1950s and numbered from his trial plots. Because they're sterile they set no seed and can't invade, so you plant them once and increase them only by dividing the crown. Bocking 14 is the one most gardeners want: rust-resistant, the highest in potassium, with a deep taproot that mines minerals for chop-and-drop fertilizer. Bocking 4 is the beefier forage strain.

Bocking 14

Zones3-9Diseaseexcellent (best comfrey-rust resistance)Size~2-3 ft; slender wingless stems

The garden standard and the strain you'll usually find. Sterile — sets no seed — with the highest potassium of any comfrey (~7% potash) and the top rust resistance. Its thin flower stems break down fast, so it's the pick for chop-and-drop mulch, compost activation, and 'comfrey tea'. Slightly higher pyrrolizidine alkaloids than Bocking 4, so keep it out of the kitchen and off livestock feed.

Where to buy ‘Bocking 14’

Story Thyme Farms may earn a small commission from these links, at no cost to you — it never changes what we recommend.

EtsyBrowse growers↗

Bocking 4

Zones4-9Diseasegood; a little more rust-prone than 14Size~3-4 ft; thicker officinale-like stems

The forage strain: deeper-rooted and more drought-hardy, with more protein and lower pyrrolizidine alkaloids — the safer pick where it'll be grazed or eaten. Also sterile. Choose Bocking 4 for animal fodder; choose Bocking 14 for feeding the soil.

Where to buy ‘Bocking 4’

Story Thyme Farms may earn a small commission from these links, at no cost to you — it never changes what we recommend.

EtsyBrowse growers↗

Sources & plant ID

Where the care distinctions come from, and how the plant is filed.

Research basis

Sources behind this profile

No extension citations are attached to comfreyyet. The care figures below come from the library's own catalogue rather than a traced primary source.

Plant ID

BinomialSymphytum × uplandicum

FamilyBoraginaceae

TypePerennial

USDA symbolSYUP

OriginIntroduced

Invasive riskSpreads aggressively

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Where to buy

Third-party nurseries — not Story Thyme Farms.

Third-party nurseries, not Story Thyme Farms. Prices are theirs.

Story Thyme Farms may earn a small commission from these links, at no cost to you — it never changes what we recommend.

EtsyBrowse growers↗

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Questions

Comfrey questions, answered straight.

Is comfrey safe for kids and pets?

With care. Never take internally — pyrrolizidine alkaloids cause sinusoidal obstruction syndrome and severe liver injury (FDA asked manufacturers to remove oral comfrey supplements in 2001). Topical use only, on intact skin, in short courses (EMA: about 10 days; Germany caps 4-6 weeks a year). Avoid in pregnancy and breastfeeding, and use caution on children. Site it accordingly if children or pets roam the garden. This is general reference, not medical or veterinary advice — call a vet or poison control if something has actually been eaten.

When do you harvest comfrey?

Cut 3-4 times/season.

What grows well with comfrey?

Proven companions include fruit trees (chop-and-drop mulch under them) — the full companion list, and what to keep away, is in the Growing tab above.

How do you propagate comfrey?

Root cuttings or crown division only — sterile, sets no seed.

Is comfrey invasive?

It can be an aggressive spreader — give it room or a barrier, and check your state's invasive-species list before planting.

Elsewhere

Where comfrey sits in the library.

Where comfrey sits in the library

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