Comfrey
A coarse, deep-rooted perennial that flowers for months and is worked almost exclusively by long-tongued bumblebees — and by short-tongued ones that have learned to cheat. Comfrey's hanging tubular bells are too deep for a honey bee to enter, so short-tongued bumblebees bite a hole at the base and steal the nectar, and honey bees then use the holes. It is the clearest demonstration of nectar robbing available in an ordinary garden.
Caution
Contains pyrrolizidine alkaloids and is hepatotoxic. Internal use as a herbal remedy is restricted or advised against in several countries, and it should not be eaten despite its long folk history as knitbone.
Value to bees
- Nectar
- Very high
- Pollen
- Moderate
- As a honey crop
- Feeds the colony but rarely yields a surplus
- Which bees, and why
- The defining plant for observing nectar robbing. Long-tongued bumblebees such as the garden bumblebee feed legitimately through the front. Short-tongued species bite a slit in the side of the corolla and take the nectar without touching the anthers — and honey bees, which cannot make the hole themselves, then queue up to use it. Watching a comfrey clump for five minutes teaches more about flower access than any diagram.
A deep tubular corolla that excludes short-tongued bees entirely by the front door. This is the textbook case for why 'attracts bees' means little without knowing which bees.
- Worth knowing
- Exceptional nectar, but genuinely restricted by flower shape — which is why the separate rating for accessibility matters more here than almost anywhere else.
Flowering
- In flower
- May to September (northern hemisphere)
Very long, and extended further by cutting: comfrey cut for compost regrows and reflowers within weeks, so a plant can be harvested three times a season and still feed bees.
- When nectar flows
- One of the heaviest nectar producers in a temperate garden, and it keeps secreting in dull and damp weather when Mediterranean plants stop.
- Year-to-year variation
- Extremely reliable. Not a honey crop at any scale.
Growing it
- Conditions
- Sun or part shade, any soil, and moisture. Effectively indestructible once established.
- Size
- 60-120 cm.
- Native range
- Europe and western Asia; naturalised widely.
- Suits
- Large gardens, Meadow or wildflower area, Hedgerow, Small gardens
- Plant the sterile cultivar 'Bocking 14' if you want it contained — the wild species self-seeds enthusiastically and the roots regenerate from any fragment left in the ground.
- Cut it two or three times a season for compost or liquid feed; it regrows and reflowers each time, so the gardening use and the bee use do not conflict.
- Site it where you intend it to stay. Comfrey is very difficult to remove once its taproot is down.
What it looks like
A vigorous clump-forming perennial with large coarse bristly leaves and nodding one-sided clusters of tubular bell flowers in cream, pink, purple or blue, uncoiling as they open.
Sources
- Bumblebees: Behaviour, Ecology, and Conservation — Oxford University Press (2010) · Monograph
- Field Guide to the Bees of Great Britain and Ireland — Bloomsbury (2015) · Field guide
How sources are selected and weighted is set out in the sources and evidence policy.
Guides covering this plant
- Nectar plants explainedNectar is a payment. Understanding what the plant is buying, and how it controls the price, explains most of what flowers do and why some are useless to some bees.
- How to make a garden genuinely useful to beesMost bee-friendly advice covers flowers in June, which is the one thing bees are least short of. The gaps are at the ends of the year — and half the problem is not flowers at all.
- Summer plants for beesSummer looks abundant and contains a real gap. The weeks between the spring blossom finishing and high summer starting are thinner than most gardens realise, and colonies are at peak population when it happens.
- Buzz pollination explainedAround 6 to 8 per cent of flowering plants lock their pollen inside tubes that open through a single pore, and release it only to a bee that grips the flower and vibrates. Honey bees cannot do it, which is why tomatoes are pollinated by bumblebees.
- Visiting a flower is not the same as pollinating itA bee on a flower may be pollinating it, robbing it, or doing nothing for it at all. The distinction is why 'attracts bees' on a plant label tells you almost nothing, and why visit counts are a poor measure of pollination.
- Plants for bumblebeesLong tongues, big bodies, cold tolerance and an annual colony that has to build from a single queen. Bumblebees can use flowers honey bees cannot reach, and they need forage at both ends of the year when honey bees are indoors.
Tools for planning planting
- Flowering calendar
What should I plant so that something is always in flower for bees?
- Bee-friendly garden planner
What should I plant in the space I actually have?
- Plant recommendation tool
Which plant fills this specific gap?