Common comfrey

Common comfrey: how do you recognise it?

Habit

Vigorous clump 60 cm to 1 m tall and about 60 cm wide, with upright, winged stems.

Leaves

Large and lance-shaped, up to 25 cm long, rough with bristly hairs; the leaf base runs down the stem as a wing.

Flower

Drooping tubular bells in curled clusters, creamy white, pink or purple-violet, from May to July.

Roots

Thick, branching taproots, black outside and white inside, reaching more than a metre deep.

Seed

Four small black nutlets per flower; it self-seeds readily.

Flowering: May–July · Plants: March–April and September–October · Pruning: July and October

Why grow it?

• One of the best bee plants: bumblebees visit the bells from May to July.
• The leaves make a potassium-rich liquid feed for tomatoes, beans and flowering plants.
• Fresh leaves make a good mulch and a quick activator for the compost heap.
• Native and tough: it grows in sun or shade, even in wet soil.
• After a hard cut it soon regrows, so you get leaves several times a year.

Common comfrey: where does it grow best?

• Sun, partial shade or shade; it flowers most freely in sun.
• Fertile soil: sand, loam, clay or peat, slightly acid to chalky.
• Ordinary to wet soil: ideal by a ditch, at a pond edge or in a damp corner.
• Give it 60–90 cm of space in a permanent spot: once planted, it is hard to get rid of.

Light

Sun, partial shade and shade

Soil type

Sand, loam, clay or peat

Acidity

Not fussy

Moisture

Normal or wet

Size

1 m tall, 0.6 m wide

Hardiness

Hardy (to -30 °C)

Goes well with

• Fruit trees: Under or beside fruit trees it supplies leaves for mulch every year.
• Purple loosestrife: Purple flower spikes in summer, in the same damp spot.
• Hemp agrimony: Flowers in late summer and attracts butterflies, also by water.
• Meadowsweet: Creamy, fragrant plumes for a wet border.

Common comfrey: when and how to plant it?

Plant in March–April and September–October.

1. Plant in March–April or September–October.
2. Choose a permanent spot, for example a corner of the vegetable garden or next to the compost heap.
3. Dig a generous hole and mix in compost or well-rotted manure: it is a hungry plant.
4. Plant at the same depth as in the pot, or lay a piece of root horizontally 5 cm deep.
5. Leave 60–90 cm between plants.
6. Water well and keep the soil moist until it is growing strongly.

Care

Watering

Only water young plants in dry spells; an established plant draws moisture from deep down.

Feeding

A layer of compost or manure in spring: the richer the soil, the more leaves.

Harvesting leaves

Cut or mow the leaves to 5 cm above the ground when the plant is 50–60 cm tall; this can be done 2–4 times a year. Wear gloves against the rough hairs.

Making liquid feed

Steep about 1 kg of fresh leaves in 10 litres of rainwater for 2–4 weeks in a covered butt. Dilute 1 to 10 before use; it smells strongly.

Mulching

Lay wilted leaves around tomatoes, beans and fruit bushes, or mix them into the compost.

Tip: Use the leaves for liquid feed and mulch, but plant it where it can stay: it roots deeply and keeps coming back. If you do not want seedlings, choose Russian comfrey ‘Bocking 14’, which does not set viable seed.

Common comfrey: when to prune it?

Pruning months: July and October.

When: After the first flowering, in July, you can cut the whole plant back. In October, clear away the dead leaves.

How:

• After flowering, cut all stems and leaves back to 5 cm above the ground; new leaves appear within a few weeks.
• For the bumblebees, you can leave part of the clump standing and cut it back later.
• Cut off the flower stems before the seed ripens if you do not want seedlings.
• In October, clear the dead leaves or leave them as a mulch.

Caution: Wear gloves and long sleeves: the bristly hairs on leaves and stems can irritate the skin.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In March–April or October: slice off a piece of the clump with roots using a sharp spade and replant it elsewhere.

Root cuttings

In winter or early spring: lay 5 cm pieces of root horizontally 5 cm deep in the ground or in a pot. They sprout readily.

Seed

It self-seeds; you can also sow outdoors in autumn or spring.

Common comfrey: how does it get through the winter?

Hardy to −30 °C.

• Very hardy, to about −30 °C: it never needs protection.
• The leaves die back in autumn; the plant regrows in March.
• Feel free to leave the dead leaves as a mulch, or put them on the compost heap.

Diseases and pests

• Rust: Orange pustules on the leaves, especially in spring. Remove affected leaves and do not compost them.
• Powdery mildew: White powder on the leaves in a dry late summer. Cut the plant back; the new leaves are usually healthy.
• Slugs: They eat young shoots in spring. An established plant soon outgrows the damage.
• Flopping: After rain the tall stems fall over. Cutting back after flowering gives a more compact plant.
• Spreading: Seedlings and new shoots outside its spot. Dig them out young, roots and all; every piece of root regrows.

Through the year

• March: Planting. Add compost or manure.
• April: Planting or dividing.
• May: Flowering. First leaves to harvest for liquid feed.
• June: Flowering. Harvest leaves for liquid feed and mulch.
• July: After flowering, cut back to 5 cm.
• August: Harvest the new leaves for liquid feed and mulch.
• September: Planting. Last leaf harvest.
• October: Planting. Clear dead leaves or leave them as a mulch.
• December: Rest. Take root cuttings in mild weather.

Edible and useful

Not edible. Comfrey contains pyrrolizidine alkaloids that can seriously damage the liver: do not eat the leaves (not even fried) and do not drink comfrey tea. What is more, young comfrey leaves are mistaken for those of the highly poisonous foxglove. It is an excellent garden plant, though: as a green manure, in the compost and as a liquid plant feed. If any is swallowed, call a poison centre (in Belgium 070 245 245) or your doctor at once.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• Some short-tongued bumblebees bite a small hole at the base of the flower to reach the nectar without pollinating it.
• ‘Bocking 14’ is named after the English village of Bocking, where comfrey varieties were compared for their leaf yield in the 1950s.
• In common comfrey the leaf bases run down the stem as wings: this is how you recognise the species.