HoneyHQ

Specialist bees and the plants they cannot do without

A large minority of bee species collect pollen from one plant genus and will starve rather than switch. For them a flowery garden is not forage — it is scenery around the one thing they need.

PollinationReviewed 2026-08-03

Two ways to be a bee

A polylectic bee collects pollen from whatever is available and productive. The honey bee is the extreme case: a colony will work a mass-flowering crop while it lasts and move to something else when it does not, and flower constancy within a single foraging trip is a tactic rather than a limitation.

An oligolectic bee will not do this. It provisions its brood cells with pollen from one genus, sometimes one species, and offered anything else it will fly on or fail to reproduce. Larvae of some specialists cannot develop on the wrong pollen even if it is provided, so this is a physiological constraint rather than a preference.

What follows from the difference
TraitGeneralistSpecialist
Pollen sourcesMany familiesOne genus or family
Flight periodLong, often the whole seasonShort, matched to the host's flowering
Response to landscape changeBuffered — can switchDirect — loses the host, loses everything
Visible in flower countsYes, often dominantEasily missed; brief and low in number
What a garden must doOffer continuous forageOffer the specific plant, in flower, at the right weeks

The examples worth knowing

  • The ivy bee, Colletes hederae, emerges in September and works ivy almost exclusively — a specialist whose host is one of the commonest plants in Britain, which is why it is thriving and spreading north.
  • Andrena species on willow: several mining bees fly for a few weeks in early spring and depend on willow catkins, which is why goat willow is worth more than its appearance suggests.
  • Squash bees in the Americas, which collect only from Cucurbita and are frequently the main pollinator of a squash crop before honey bees are awake.
  • Harebell carpenter bee, Chelostoma rapunculi, restricted to Campanula — a garden with bellflowers has it and a garden without does not.
  • Poppy-collecting Osmia and Hoplitis species, which use petal pieces as well as pollen.

Why this changes what a bee garden is for

Counting visits to a flowering border tells you about generalists, because generalists are what a border attracts. The specialists are elsewhere, on the untidy edges and the native plants, in numbers too small and over periods too short to show up. A garden optimised only for visible activity will look successful while supporting a narrowing set of species.

  • Include native plants of the genera your local specialists use — willow, ivy, campanula, knapweed, scabious in Britain; goldenrod, aster, milkweed and cucurbits in much of North America.
  • Do not tidy the flowering period away. Cutting a plant back before or during flowering removes the entire year's provision for a bee tied to it.
  • Leave bare ground and stems. Specialists are overwhelmingly solitary, and nest sites limit them as often as forage does.
  • Accept plants that look weedy. Several important host genera are exactly the things a tidy garden removes first.

The claims on this page

Every substantive claim is placed on a tier, and the top two tiers must also state what they are not claiming.

Emerging research

Real studies exist and point somewhere, but they are small, in vitro, in animals, or not yet replicated. Direction is not the same as a result.

Emerging research

A substantial minority of solitary bee species are pollen specialists restricted to one plant genus or family.

Figures around a third of species are commonly reported for temperate faunas, with higher proportions in arid regions. The exact share depends on how strictly specialisation is defined and on how well the fauna has been studied, so estimates vary between regions and authors.

What this does not claim: This is not a precise global figure, and it should not be read as one. Specialisation is a spectrum rather than a binary, diet breadth is unknown for many species, and the well-studied faunas that produce these estimates are mostly European and North American.

  • The Bees of the World — Johns Hopkins University Press (2007) · Textbook
  • Field Guide to the Bees of Great Britain and Ireland — Bloomsbury (2015) · Field guide

Sources

  • The Bees of the World — Johns Hopkins University Press (2007) · Textbook
  • Field Guide to the Bees of Great Britain and Ireland — Bloomsbury (2015) · Field guide
  • Assessment Report on Pollinators, Pollination and Food Production — Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) (2016) · Systematic review Link

How sources are selected and weighted is set out in the sources and evidence policy.

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