Red mason bee
Osmia bicornis
Bee
The red mason bee (Osmia bicornis) is a solitary, cavity-nesting bee in the family Megachilidae, named for its habit of sealing nest cells with mud in pre-existing hollows such as mortar joints, hollow stems, and bee hotels. It is the most familiar solitary bee in British and northwest European gardens, flying from April through June or July (occasionally from late March) on a single annual generation. A polylectic forager, it ranges widely across spring-flowering plants; pollen provisions favour maple and oak, and it visits fruit blossom including apple, plum, and pear, making it a valued pollinator for orchards and kitchen gardens. Mean foraging distances are typically around 100–150 m from the nest, with a maximum recorded range of around 600 m, and its readiness to occupy artificial nest tubes makes it highly compatible with garden habitats across Europe and parts of North Africa and the Near East.
Plan for this species
Location-fit plant set for Chicago, IL: host and specialist plants first, then nectar, fruit, seed, foliage, and shelter plants that still fit the current and mid-century climate read.
0 essential relationships / 4 supporting plants
Host/specialist links: 0
Forage/pollination links: 4
Shelter links: 0
Relationship roles: 3
Sweet cherry
Supporting / Plants this species pollinates
A documented supplemental orchard pollinator of sweet cherry (Prunus avium); trials improved fruit size, weight, and harvest consistency (no change in fruit-set number).
Comfrey
Supporting / Nectar plants
Observed nectar-robbing comfrey - biting the base of the corolla rather than entering the flower - so an opportunistic feed rather than a pollination service.
European plum
Supporting / Pollen plants
BWARS lists plum (Prunus domestica) among its spring fruit-blossom forage.
Yellow flag iris
Supporting / Pollen plants
Osmia bicornis, long catalogued as O. rufa, appears in the European visitor list for this species. A solitary bee of this size collects pollen from the anther without reliably completing the pollination circuit, so it is recorded as a forager rather than a pollinator.
Plants in the catalog
Plants this species pollinates · 1
A documented supplemental orchard pollinator of sweet cherry (Prunus avium); trials improved fruit size, weight, and harvest consistency (no change in fruit-set number).
Nectar plants · 1
Observed nectar-robbing comfrey - biting the base of the corolla rather than entering the flower - so an opportunistic feed rather than a pollination service.
Pollen plants · 2
BWARS lists plum (Prunus domestica) among its spring fruit-blossom forage.
Osmia bicornis, long catalogued as O. rufa, appears in the European visitor list for this species. A solitary bee of this size collects pollen from the anther without reliably completing the pollination circuit, so it is recorded as a forager rather than a pollinator.
Range
Native across the western Palaearctic: from Sweden and Denmark south through mainland Europe to Spain and Morocco, east through Turkey and the Near East to Iran. Widespread and locally common throughout Britain as far north as Perthshire; established in Ireland since around 2003, currently known from Belfast, Dublin, and Cork. Conservation status: Least Concern (IUCN).
Sources & citations
Cite this page
Use this citation for the Plotwright wildlife record. Use the source cards below to explore the references that informed its taxonomy, range, conservation, host plants, foraging, and habitat.
Plotwright. (n.d.). Red mason bee (Osmia bicornis). Retrieved 2026, August 20, from https://plotwright.com/wildlife/red-mason-bee
Sources used for this record
This record is compiled from the sources below.
Osmia bicornis - Wikipedia
Identification, the western-Palaearctic range, Least Concern status, the single spring generation, and mud-cell cavity nesting.
Osmia bicornis - BWARS
British range, cavity and bee-hotel nesting, the spring fruit-blossom forage list (including plum), and garden affinity.
GBIF: Osmia bicornis
GBIF match is exact and accepted for Osmia bicornis in family Megachilidae, the name under which the older Osmia rufa is now placed.
iNaturalist: Osmia bicornis
iNaturalist returns the active species Osmia bicornis, the red mason bee.