There’s a bee you’ve almost certainly never heard of. Orchard growers know her well.
Meet Osmia lignaria. The blue orchard mason bee.
She’s native to the United States and Canada, and she’s one of the best fruit-tree pollinators we have. Just 250 to 300 females can pollinate an entire acre of apples or cherries. She keeps working under cloudy skies and in cooler weather than most bees will. Growers use her on her own or alongside honeybees. She carries pollen on the underside of her belly instead of on her legs.
She doesn’t make honey. She doesn’t live in a colony. She doesn’t have a queen. She almost never stings.
She just does the hard work of pollinating our food and a lot of early spring flowers. Alone. Every day of a four-to-six-week life.
Why you’ve never seen one
The blue orchard mason bee is about the size of a honeybee, but rounder and metallic blue-black. In flight, she’s often mistaken for a black fly rather than a bee. She’s solitary. She doesn’t swarm. She doesn’t announce herself.
She finds a beetle hole in dead wood, or a hollow stem, and gets to work. She packs a ball of pollen into the back of the tunnel, lays one egg on it, and seals it in with a wall of mud. Then she does it again. A single cell takes 12 to 25 pollen trips, and a nest holds roughly seven to eleven cells.
She chooses who goes where. Her daughters go in first, at the back. Her sons go last, near the door. In spring, the males chew out first and hover around the entrance, waiting for the females to emerge.
She never meets any of them. She’s gone before her young finish developing. They spend the summer growing, spin cocoons, and wait out the winter as adults inside the nest, ready for next spring.
Her entire existence depends on finding a tunnel. About 30 percent of North America’s roughly 4,000 native bee species nest in tunnels like hers, in beetle holes in dead wood and in hollow or pithy stems.
That’s the problem.
The housing crisis for our tunnel-nesting bees
We’ve spent decades tidying up the natural world. Dead trees get removed. Hollow stems get cut back. Old wooden fence posts get replaced with metal. Garden beds get mulched to perfection.
Every one of those decisions takes away potential nesting habitat for the blue orchard mason bee and the other tunnel nesters. The absence of these features in intensively farmed landscapes can limit nesting for the crop pollinators that need them.
A bee with nowhere to nest can’t raise young, and fewer young this year means fewer bees pollinating your apple tree next spring.
Where she lives
The blue orchard mason bee is native across much of the United States and southern Canada, in two subspecies. The western one, propinqua, lives west of about the 100th meridian. The eastern one, lignaria, lives east of it. The Rocky Mountains are the usual dividing line.
Warm winters keep her out of Florida and parts of the Gulf Coast. Records are also thin across the central plains, probably because there isn’t much suitable nesting habitat.
The map below shows where she’s native, and you can switch it to the subspecies view. Of 50 states, we found 42 in her native range, 6 uncertain, and 2 where she isn’t native. In Canada, 6 of 13 provinces and territories are in her native range, 1 is uncertain, and 6 aren’t.
Where the blue orchard bee is native
Native range by state. Tap or hover a state.
Only the western subspecies is sold commercially. These bees are adapted to the climate where they live. If you’re in the east, the bees already living near you are the ones to help.
Every state and province in plain text
AlabamaNative range
Status: Native range.
What we found: Native range. 31 GBIF records, 0 identified as western (propinqua) and 27 as eastern (lignaria). UF/IFAS says she isn’t found along the warm Gulf Coast, so expect her in the northern part of the state.
Source: gbif.org
AlaskaUncertain or data-sparse
Status: Uncertain or data-sparse.
What we found: Uncertain. SARE’s mason bee guide lists southern Alaska in the range, but GBIF has no records there. We left it as a judgment call.
Source: sare.org
ArizonaNative range
Status: Native range.
What we found: Native range. 53 GBIF records, 14 identified as western (propinqua) and 3 as eastern (lignaria).
Source: gbif.org
ArkansasNative range
Status: Native range.
What we found: Native range. 18 GBIF records, 0 identified as western (propinqua) and 5 as eastern (lignaria).
Source: gbif.org
CaliforniaNative range
Status: Native range.
What we found: Native range. 3,057 GBIF records, 2,913 identified as western (propinqua) and 6 as eastern (lignaria).
Source: gbif.org
ColoradoNative range
Status: Native range.
What we found: Native range. 578 GBIF records, 532 identified as western (propinqua) and 0 as eastern (lignaria).
Source: gbif.org
ConnecticutNative range
Status: Native range.
What we found: Native range. 13 GBIF records, 0 identified as western (propinqua) and 1 as eastern (lignaria).
Source: gbif.org
DelawareUncertain or data-sparse
Status: Uncertain or data-sparse.
What we found: Uncertain. Only 4 GBIF records here, not enough to call it native range with confidence.
Source: gbif.org
FloridaNot native or not recorded
Status: Not native or not recorded.
What we found: Not native. UF/IFAS says warm winters keep the bee out of Florida and parts of the southeastern Gulf Coast. GBIF has one record here.
Source: ask.ifas.ufl.edu
GeorgiaNative range
Status: Native range.
What we found: Native range. 16 GBIF records, 0 identified as western (propinqua) and 4 as eastern (lignaria). UF/IFAS says she isn’t found along the warm Gulf Coast, so expect her in the northern part of the state.
Source: gbif.org
HawaiiNot native or not recorded
Status: Not native or not recorded.
What we found: Not native. GBIF has no records, and the range USDA and extension sources describe doesn’t include Hawaii.
Source: gbif.org
IdahoNative range
Status: Native range.
What we found: Native range. 124 GBIF records, 104 identified as western (propinqua) and 0 as eastern (lignaria).
Source: gbif.org
IllinoisNative range
Status: Native range.
What we found: Native range. 188 GBIF records, 0 identified as western (propinqua) and 9 as eastern (lignaria).
Source: gbif.org
IndianaNative range
Status: Native range.
What we found: Native range. 374 GBIF records, 1 identified as western (propinqua) and 2 as eastern (lignaria).
Source: gbif.org
IowaNative range
Status: Native range.
What we found: Native range. 21 GBIF records, 0 identified as western (propinqua) and 19 as eastern (lignaria).
Source: gbif.org
KansasNative range
Status: Native range.
What we found: Native range. 155 GBIF records, 2 identified as western (propinqua) and 33 as eastern (lignaria).
Source: gbif.org
KentuckyNative range
Status: Native range.
What we found: Native range. 173 GBIF records, 2 identified as western (propinqua) and 2 as eastern (lignaria).
Source: gbif.org
LouisianaUncertain or data-sparse
Status: Uncertain or data-sparse.
What we found: Uncertain. Only 6 GBIF records here, not enough to call it native range with confidence.
Source: gbif.org
MaineNative range
Status: Native range.
What we found: Native range. 94 GBIF records, 0 identified as western (propinqua) and 64 as eastern (lignaria).
Source: gbif.org
MarylandNative range
Status: Native range.
What we found: Native range. 189 GBIF records, 0 identified as western (propinqua) and 20 as eastern (lignaria).
Source: gbif.org
MassachusettsNative range
Status: Native range.
What we found: Native range. 71 GBIF records, 0 identified as western (propinqua) and 10 as eastern (lignaria).
Source: gbif.org
MichiganNative range
Status: Native range.
What we found: Native range. 109 GBIF records, 0 identified as western (propinqua) and 48 as eastern (lignaria).
Source: gbif.org
MinnesotaNative range
Status: Native range.
What we found: Native range. 90 GBIF records, 0 identified as western (propinqua) and 35 as eastern (lignaria).
Source: gbif.org
MississippiNative range
Status: Native range.
What we found: Native range. 58 GBIF records, 0 identified as western (propinqua) and 29 as eastern (lignaria). UF/IFAS says she isn’t found along the warm Gulf Coast, so expect her in the northern part of the state.
Source: gbif.org
MissouriNative range
Status: Native range.
What we found: Native range. 46 GBIF records, 0 identified as western (propinqua) and 6 as eastern (lignaria).
Source: gbif.org
MontanaNative range
Status: Native range.
What we found: Native range. 39 GBIF records, 35 identified as western (propinqua) and 0 as eastern (lignaria).
Source: gbif.org
NebraskaNative range
Status: Native range.
What we found: Native range. 60 GBIF records, 0 identified as western (propinqua) and 49 as eastern (lignaria).
Source: gbif.org
NevadaNative range
Status: Native range.
What we found: Native range. 111 GBIF records, 98 identified as western (propinqua) and 0 as eastern (lignaria).
Source: gbif.org
New HampshireNative range
Status: Native range.
What we found: Native range. 31 GBIF records, 0 identified as western (propinqua) and 4 as eastern (lignaria).
Source: gbif.org
New JerseyNative range
Status: Native range.
What we found: Native range. 24 GBIF records, 0 identified as western (propinqua) and 18 as eastern (lignaria).
Source: gbif.org
New MexicoNative range
Status: Native range.
What we found: Native range. 25 GBIF records, 5 identified as western (propinqua) and 0 as eastern (lignaria).
Source: gbif.org
New YorkNative range
Status: Native range.
What we found: Native range. 242 GBIF records, 0 identified as western (propinqua) and 213 as eastern (lignaria).
Source: gbif.org
North CarolinaNative range
Status: Native range.
What we found: Native range. 203 GBIF records, 0 identified as western (propinqua) and 11 as eastern (lignaria).
Source: gbif.org
North DakotaUncertain or data-sparse
Status: Uncertain or data-sparse.
What we found: Uncertain. Only 1 GBIF record here, not enough to call it native range with confidence.
Source: gbif.org
OhioNative range
Status: Native range.
What we found: Native range. 48 GBIF records, 0 identified as western (propinqua) and 24 as eastern (lignaria).
Source: gbif.org
OklahomaNative range
Status: Native range.
What we found: Native range. 50 GBIF records, 0 identified as western (propinqua) and 19 as eastern (lignaria).
Source: gbif.org
OregonNative range
Status: Native range.
What we found: Native range. 1,002 GBIF records, 330 identified as western (propinqua) and 1 as eastern (lignaria).
Source: gbif.org
PennsylvaniaNative range
Status: Native range.
What we found: Native range. 142 GBIF records, 1 identified as western (propinqua) and 28 as eastern (lignaria).
Source: gbif.org
Rhode IslandUncertain or data-sparse
Status: Uncertain or data-sparse.
What we found: Uncertain. GBIF has no records here, though neighboring Connecticut and Massachusetts have the bee. Likely a data gap, but unconfirmed.
Source: gbif.org
South CarolinaNative range
Status: Native range.
What we found: Native range. 35 GBIF records, 0 identified as western (propinqua) and 13 as eastern (lignaria).
Source: gbif.org
South DakotaNative range
Status: Native range.
What we found: Native range. 14 GBIF records, 12 identified as western (propinqua) and 0 as eastern (lignaria).
Source: gbif.org
TennesseeNative range
Status: Native range.
What we found: Native range. 57 GBIF records, 0 identified as western (propinqua) and 16 as eastern (lignaria).
Source: gbif.org
TexasNative range
Status: Native range.
What we found: Native range. 104 GBIF records, 3 identified as western (propinqua) and 27 as eastern (lignaria).
Source: gbif.org
UtahNative range
Status: Native range.
What we found: Native range. 1,202 GBIF records, 1,136 identified as western (propinqua) and 4 as eastern (lignaria).
Source: gbif.org
VermontNative range
Status: Native range.
What we found: Native range. 144 GBIF records, 0 identified as western (propinqua) and 19 as eastern (lignaria).
Source: gbif.org
VirginiaNative range
Status: Native range.
What we found: Native range. 159 GBIF records, 0 identified as western (propinqua) and 60 as eastern (lignaria).
Source: gbif.org
WashingtonNative range
Status: Native range.
What we found: Native range. 1,029 GBIF records, 617 identified as western (propinqua) and 1 as eastern (lignaria).
Source: gbif.org
West VirginiaNative range
Status: Native range.
What we found: Native range. 75 GBIF records, 0 identified as western (propinqua) and 15 as eastern (lignaria).
Source: gbif.org
WisconsinUncertain or data-sparse
Status: Uncertain or data-sparse.
What we found: Uncertain. Only 8 GBIF records here, not enough to call it native range with confidence.
Source: gbif.org
WyomingNative range
Status: Native range.
What we found: Native range. 31 GBIF records, 28 identified as western (propinqua) and 0 as eastern (lignaria).
Source: gbif.org
AlbertaNative range
Status: Native range.
What we found: Native range. 51 GBIF records, 26 identified as western (propinqua) and 19 as eastern (lignaria). Both subspecies turn up here.
Source: search.wildspecies.ca
British ColumbiaNative range
Status: Native range.
What we found: Native range. 875 GBIF records, 404 identified as western (propinqua) and 2 as eastern (lignaria).
Source: search.wildspecies.ca
ManitobaNative range
Status: Native range.
What we found: Native range. 15 GBIF records, 0 identified as western (propinqua) and 7 as eastern (lignaria). WildSpecies calls its status unrankable for lack of data.
Source: search.wildspecies.ca
New BrunswickNative range
Status: Native range.
What we found: Native range. 26 GBIF records, 0 identified as western (propinqua) and 11 as eastern (lignaria). WildSpecies calls its status unrankable for lack of data.
Source: search.wildspecies.ca
Newfoundland and LabradorNot native or not recorded
Status: Not native or not recorded.
What we found: Not native or not recorded. WildSpecies lists the bee as not present, and GBIF has no records.
Source: search.wildspecies.ca
Northwest TerritoriesNot native or not recorded
Status: Not native or not recorded.
What we found: Not native or not recorded. WildSpecies lists the bee as not present, and GBIF has no records.
Source: search.wildspecies.ca
Nova ScotiaNot native or not recorded
Status: Not native or not recorded.
What we found: Not native. Researchers introduced the bee to the Annapolis Valley for orchard pollination trials, and WildSpecies lists it as not present. GBIF has 4 records. We treat Nova Scotia as introduced, which is a judgment call.
Source: entsocont.ca
NunavutNot native or not recorded
Status: Not native or not recorded.
What we found: Not native or not recorded. WildSpecies lists the bee as not present, and GBIF has no records.
Source: search.wildspecies.ca
OntarioNative range
Status: Native range.
What we found: Native range. 98 GBIF records, 0 identified as western (propinqua) and 29 as eastern (lignaria).
Source: search.wildspecies.ca
Prince Edward IslandNot native or not recorded
Status: Not native or not recorded.
What we found: Not native or not recorded. WildSpecies lists the bee as not present, and GBIF has no records.
Source: search.wildspecies.ca
QuebecNative range
Status: Native range.
What we found: Native range. 48 GBIF records, 0 identified as western (propinqua) and 23 as eastern (lignaria).
Source: search.wildspecies.ca
SaskatchewanUncertain or data-sparse
Status: Uncertain or data-sparse.
What we found: Uncertain. GBIF has 3 records. WildSpecies listed the bee here as secure in 2015, then as unrankable in 2020 for lack of data.
Source: search.wildspecies.ca
YukonNot native or not recorded
Status: Not native or not recorded.
What we found: Not native or not recorded. WildSpecies lists the bee as not present, and GBIF has no records.
Source: search.wildspecies.ca
The good news
You can add nesting habitat this weekend.
She doesn’t need wilderness. She doesn’t need acres of habitat. She needs a hole in a piece of wood about the width of a pencil, mud nearby to seal her cells, flowers in early spring, and a nest that stays clean.
Build or buy a mason bee house. Drill holes 5/16 inch wide and 6 inches deep into an untreated block of wood. Face it east so the morning sun hits the entrance, but keep it out of the hot afternoon sun, which can kill the young. Mount it a few feet off the ground on something that doesn’t sway. Pre-made houses work too. Just check the tube diameter and depth.
Keep it clean. This is the part most bee houses skip. Mites and fungal disease build up in old tunnels. Use paper straws that you can pull out each fall, and replace the whole block or bundle every two years.
Leave stems standing. When you cut back perennials, leave the dead stems for the winter. Hollow and pithy stems, like raspberry canes, give cavity-nesting bees a place to raise young. Our guide to when to cut back native plants has the timing.
Leave dead wood alone. That old fence post. The dead branch on the apple tree. The rotting log in the corner of the yard. They aren’t eyesores. They’re bee apartment buildings.
Plant for early spring. She flies for only a few weeks, so she needs nectar and pollen the moment she emerges. She works apple, cherry, pear, and plum blossoms, and caneberries. In California almond orchards, planted wildflowers improved her reproduction. Pick native plants that bloom while she’s flying.
Go easy on insecticides. Bees can’t tell a pest from a pollinator, so skip the spray on anything in bloom.
The bigger picture
Honeybees get most of the attention. They’re the bee we worry about and rally around.
But North America has about 4,000 native bee species. Most are solitary. About 30 percent nest in tunnels, like the blue orchard mason bee. The other 70 percent nest in the ground, and they need bare, sunny soil. Thick mulch and wall-to-wall lawn leave them nowhere to dig.
The blue orchard mason bee is just one of them. But she’s a good place to start.
Drill a hole. Leave a stem. Plant something native. She’ll find it.
Sources
- USDA Agricultural Research Service, Blue Orchard Bee.
- USDA / Utah State University Extension, Blue Orchard Bee: Commercial Pollinator for Orchards.
- University of Florida IFAS, Blue orchard bee, Osmia lignaria (EENY-549).
- Sustainable Agriculture Research and Education, Managing Alternative Pollinators: Mason Bees, natural history.
- Xerces Society, Tunnel Nests for Native Bees.
- Xerces Society, Nesting resources.
- Utah State University, Blue orchard bee thesis (subspecies range).
- Boyle et al., Ecology and Evolution (2020), Wildflower plantings promote blue orchard bee reproduction in California almond orchards.
- GBIF, Osmia lignaria occurrence records.
- WildSpecies, Canada, Orchard Mason Bee (Osmia lignaria).
- Entomological Society of Ontario, Winter management options for Osmia lignaria in Nova Scotia.
