Common Bee Pollen Found in My Beehives

I have conducted a systematic analysis of pollen samples from my beehives in the North Seattle area, covering the period from 2018 to 2024 and totaling 36,250 specimens. The identification of pollen sources was based on bloom status, pollen color, and microscopic images, cross-referenced with images of pollen directly collected from each plant species. So far, 34,857 specimens (96%) have been identified to the species, genus, or family level.

On this page, I present the top 15 pollen sources for my bees across the seasons from 2018 to 2024. Since the number of pollen samples collected from the beehives varied significantly from month to month (as shown below), I have also provided monthly rankings on separate pages.

Monthly Distribution of 36,250 Specimens –Click on a month to view its ranking.

• January – 317 (0.87%)

• February – 350 (0.97%)

• March – 2,312 (6.38%)

• April – 3,890 (10.7%)

• May – 3,583 (9.9%)

• June – 5,231 (14.4%)

• July – 5,904 (16.3%)

• August - 3,859 (10.6%)

• September – 5,934 (16.4%)

• October – 4,306 (11.9%)

• November – 548 (1.5%)

• December – 16 (0.04%)

My beehives are located in a forested residential area near the north end of Lake Washington, WA. There are no large open fields nearby, except for wetlands and park lawns. Therefore, it is not surprising that common North American bee plants that thrive in open fields—such as clovers, asters (including goldenrod and sunflowers), and mustards—are not among the top 15 pollen sources (though they may appear in the monthly rankings).

Most of the pollen come from cultivated or escaped (invasive) plants, with a few exceptions:

• Bigleaf maple, vine maple, and most willow species are native.

• The native bitter cherry is included in the "Cherries, plums, and apricots" category, while the black hawthorn is included in the "Hawthorns" category, though both are minor components within their respective groups.

Below are ×800 microscopic images of the top 15 pollen types, along with graphs showing their monthly distribution.

Click to open the pollen library for the ginseng family (Google photo albums)

English ivy is the largest pollen source for my bees—even surpassing blackberry, though blackberry is likely a better nectar source. Due to ivy's strong pollen flow in fall, my bees continue rearing brood into November, and possibly even December in a mild fall. Varroa mite control during and after the ivy flow is one of my most important beekeeping tasks, even if the hives were already treated for mites earlier in the summer.

Click to open the pollen library for the genus Rubus (Google photo album)

Himalayan blackberry, a highly invasive plant, is one of the best bee forage sources in my area. It blooms later in the season compared to other brambles. Native Rubus species—such as salmonberry, Pacific blackberry, and thimbleberry—bloom in April and May, attracting honey bees. However, their pollen is difficult to distinguish from one another or from other plants in the rose family. Even if I combined all unidentified rose-family-like pollen, it still wouldn’t rank in the top 30.

Click to open the pollen library for the genus Prunus (Google photo album)

There are various Prunus trees and shrubs in my neighborhood, three of which are especially abundant. Blooming from early March, cherry plum (or flowering plum, Prunus cerasifera) can be found as either pink-flowered ornamental trees or white-flowered escaped trees/shrubs. In April, numerous escaped sweet cherry trees (P. avium) come into full bloom. Finally, in May, the native bitter cherry (P. emarginata) blooms.

Below are microscopic images of pollen specimens collected from my beehives during the respective peak blooms, resembling pollen collected directly from flowers (shown in the pollen library). It is possible, however, that the pollen could have come from other Prunus species.

Click to open the pollen library for maples (Google photo album)

Bigleaf maple is undoubtedly one of the most significant native nectar sources in spring. However, due to its sheer abundance and towering height, I rarely witness honey bees foraging on it. Proving that my bees actually work on bigleaf maple was my strongest motivation for starting pollen analysis.

Click to open the pollen library for the chicory subfamily (Google photo album)

The most common chicory subfamily plants in my neighborhood—whose pollen is indistinguishable from one another—are dandelion, cat’s ear, hawksbeard, and sow thistle (Sonchus oleraceus). However, sow thistle does not appear to attract honey bees as much.

In my forested residential neighborhood, chicory (Cichorium intybus) is uncommon, and I have detected its pollen in my beehives only twice in seven years.

In the monthly distribution graph below, pollen collected from December to April is likely from dandelions. Cat’s ear and hawksbeard begin blooming in May and June, respectively, and continue until frost. During the hot summer months, cat’s ear and hawksbeard appear to attract more honey bees than dandelions.

Click to open the pollen library for the evening primrose family (Google photo album)

Evening primrose is a biennial wildflower that grows in disturbed areas, roadsides, meadows, and gardens. It is native to the eastern and central U.S. and is considered a naturalized species here. The pollen is pale yellow and very sticky.

Click to open the pollen library for the hydrangea family (Google photo album)

Oakleaf hydrangea (Hydrangea quercifolia) and panicled hydrangea (H. paniculata) are ornamental shrubs, and their small florets in the center of large flower heads attract honey bees. The more common French hydrangeas (bigleaf hydrangea, H. macrophylla cultivars and hybrids) do not attract as many honey bees as the oakleaf and panicled varieties, as many of these cultivars only have sterile flowers.

Click to open the pollen library for the Magnolia family (Google photo album)

Southern magnolia is a popular small to medium-sized ornamental tree with large white flowers. It is one of my bees' favorite mid-summer forage plants.

Click to open the pollen library for maples (Google photo album)

Vine maple (Acer circinatum) is the other native maple, alongside the bigleaf maple, that contributes to our spring honey. It is a small tree or large shrub often found in the forest understory or used in landscaping. It has clusters of small flowers, dark reddish on the outside and greenish-yellow on the inside, which bloom a couple of weeks later than those of the bigleaf maple.

Click to open the pollen library for the apple tribe (Google photo album)

Common hawthorn (Crataegus monogyna), a highly invasive tree/shrub with white or pinkish flowers, is by far the most abundant hawthorn species. It contributes to our spring honey most years. The native black hawthorn (Douglas hawthorn, C. douglasii), which blooms around the same time, is much less common in my immediate neighborhood. Two ornamental species, Lavallee’s hawthorn (C. × lavalleei), which blooms slightly later, and Washington hawthorn (C. phaenopyrum), which blooms in June, are fairly common in my area.

Click to open the pollen library for the buckwheat family (Google photo album)

Japanese knotweed (Reynoutria japonica, also known as Fallopia japonica or Polygonum cuspidatum), is our major mid-to-late summer nectar source, producing dark, flavorful honey. It is an extremely invasive perennial in the buckwheat family, typically growing 6–10 feet tall. It has reddish, hollow stems with nodes, large, alternately arranged leaves, and erect clusters of small, creamy-white flowers

Click to open the pollen library for the willow family (Google photo album)

Various willow species thrive in my neighborhood. The first to bloom are pussy willows (Salix species that flower before their leaves emerge), such as the native Scouler’s willow (S. scouleriana) and ornamental pussy willows like the weeping French pussy willow (S. caprea ‘Pendula’). Next, another native pussy willow, Sitka willow (S. sitchensis), and the very common landscaping trees, weeping willows (Salix babylonica, S. alba, and hybrids), begin blooming in wetlands. Finally, the native Pacific willow (S. lucida) blooms in wetlands later in the season.

Click to open the pollen library for the genus Impatiens (Google photo album)

Jewelweed (Impatiens capensis), also known as orange balsam or spotted touch-me-not, is an annual plant often found in wetlands. It grows 3–5 feet tall and has serrated leaves and orange, hanging flowers with reddish spots. It is my bees’ favorite in late summer to early fall, until the ivy flow begins. Jewelweed is native to eastern North America but is considered a noxious weed in our state because it competes with and hybridizes with the native western touch-me-not (I. ecornuta), which has yellow flowers with no spots. I have not found I. ecornuta in my neighborhood.

Click to open the pollen library for the beech family and related plants (Google photo album)

Chestnut (Castanea species and hybrids) are medium- to large-sized trees with toothed leaves 6–10 inches long and long, slender catkins that bear many small, cream-yellow flowers. I believe most cultivated chestnuts are European chestnut (C. sativa, also known as sweet chestnut) and its hybrids with Asian species. According to a local arborist, several large trees in my neighborhood are American chestnut (C. dentata), which is native to parts of the eastern U.S., though I cannot easily distinguish them. My bees bring back lots of chestnut pollen around the end of the blackberry flow. Although chestnut flowers are generally considered wind-pollinated, they do produce nectar that attracts various pollinators.

Click to open the pollen library for the magnolia family (Google photo album)

Tulip poplar, also known as tulip tree or yellow poplar (Liriodendron tulipifera), is native to the eastern U.S. and is a fairly common landscaping tree in my area. It can grow very tall for a broadleaf tree, reaching up to 150 feet. It has distinctive, 4-lobed, heart-shaped leaves and greenish-yellow, tulip-like flowers. Tulip poplar bloom typically peaks between those of black locust and blackberry.