Pollinator Handouts

You can now download some of the recent handouts I created for pollinators and native plants from the right sidebar of my blog homepage.

More to come, stay tuned!

American Pasqueflower ~ A Welcome Sign of Spring

American pasqueflower ~ Anemone patens

American pasqueflower is a wonderful native alternative to tulips or daffodils, flowering in early spring. It can be found on sunny, prairie slopes with poor, dry soils. This year, it's flowering before any of the woodland ephemerals such as bloodroot, Sanguinaria canadensis. The leaves are held tight to the stem during flowering, looking like a prop holding the flower upwards. These palmately-divided leaves relax away from the stem and open after flowering.

American pasqueflower provides an abundant amount of pollen to pollinators, an important, early-spring resource for female bees to provision their nests. The plant is protogynous, developing the female parts first (stigmas), with the male anthers shedding pollen after the stigmas are no longer receptive. This is one of many fascinating strategies to ensure cross-pollination. In order to attract pollinators during the male phase, small staminal nectaries located at the base of the stamens produce nectar. It is likely that a visiting insect seeking nectar only will come into contact with the anthers transferring pollen on their bodies to the next pasqueflower.

The flowers when open, track the sun throughout the day turning the flowerheads. This solar tracking (heliotropism) tends to occur in plant families that flower when pollinators are scarce. The flowers facing the sun trap the sun's heat creating a warm place for pollinators to forage and warm body temperatures. The pollinators have little difficulty flying to the next flower when warm, aiding in the cross-pollination of the plant.

Small Sweat Bees, Lasioglossum spp. 
Frequent visitors, small sweat bees collect the white pollen which is abundant, circling around the outside of the numerous stamens on each flower.

Large Mining Bees, Andrena spp.
Large mining bees belonging to the Melandrena subgenus are common in early spring and can be mistaken for bumble bees. They have shiny, black abdomens, unlike bumble bees who have hairy abdomens. Mining bees nest in the ground in sand or loose, loam soils.

Other pollinators to look for include large syrphid flies feeding on pollen. These flies are mimics of large mining bees and bumble bees. Bumble bees also visit the flowers.

Because American pasqueflower blooms in early spring during fluctuating temperatures, insect activity can be sporadic. If the sepals are closed on a cool day, look for bees forcing their way into the flower.


References:
Bock, J. H., & Peterson, S. J. (1975). Reproductive biology of Pulsatilla patens (Ranunculaceae). American Midland Naturalist, 476-478. Retrieved from: http://www.jstor.org/stable/2424441

Wild Geranium Pollinators & Floral Visitors

Like many spring-flowering native plants, wild geranium flowers have the ability to self-pollinate when no pollinators are present. However, the flower matures to ensure cross-pollination when insects are present, with the row of outer anthers developing on the first or second day after the flowers open, followed by the inner row on the second or third day. The stigma becomes receptive after the anthers have dehisced on the third or forth day.

Bees, flies and beetles visit the flower for nectar and pollen. Nectar is secreted from five glands located between the stamens and sepals. In a study by Bertin et al, bees visiting for nectar were responsible for depositing more pollen than pollen collecting bees. Larger bees such as bumble bees and mason bees are considered effective pollinators because pollen brushed onto the underside of their abdomen contacts the stigma. Smaller bees are able to circle around the base of the stamens feeding on nectar without coming into contact with pollen from the anthers above.

Wild geranium flowers are over one inch in width and extremely showy. Dark lines on the flowers act as nectar guides, showing pollinators the location of the nectaries at the base of the stamens.

Small Carpenter Bees, Ceratina spp.
Smaller bee species circle the base of the flower seeking out nectar without coming in contact with the anthers and stigmas above.

Cuckoo Bees, Nomada spp. 
Wild geranium is a nectar source for this cuckoo bee in early spring. Female Nomada bees lay their eggs in the nests of ground nesting native bees, especially mining bees (Andrena spp.). The cuckoo bee eggs hatch and the larvae kills the host bee larvae and consumes the provisions provided by the host. Nomada bees are reddish-brown to black with yellow or white markings.

Mason Bees Osmia spp. 
Mason bees visit wild geranium for both pollen and nectar. Females land on top of the anthers gathering them together with her legs. Pollen is brushed onto the pollen-collecting hairs on the underside of the abdomen. Wild geranium is an important source of pollen and nectar for mason bees, it flowers when females are provisioning their nests.

Sweat Bees Lasioglossum spp.
Sweat bees visit the flowers to feed on nectar.

Fruitworm Beetles Byturus unicolor 
Long, dense hairs cover the elytra of these beetles where pollen grains attach. Adults emerge from the soil in early spring, feed on host plants (raspberries, blackberries and avens), mate, then lay eggs. Larvae burrow into the flower buds and fruit of the host species and buds drop off or decay. Fruit becomes misshapen and ‘wormy’. Look for adult beetles feeding on the pollen of woodland natives in early spring such as Viriginia waterleaf and wild geranium.


References 
Bertin, R. I., & Sholes, O. D. (1993). Weather, pollination and the phenology of Geranium maculatum. American Midland Naturalist, 52-66. Retrieved from: http://www.jstor.org/stable/2426435

Willson, M. F., Miller, L. J., & Rathcke, B. J. (1979). Floral display in Phlox and Geranium: adaptive aspects. Evolution, 52-63. Retrieved from: http://www.jstor.org/stable/2407365

Harebell ~ Campanula rotundifolia Pollinators & Floral Visitors

Harebell ~ Campanula rotundifolia

Typically, small to medium sized bees visit harebell flowers. The five-parted, nodding flowers have a prominent, large, central style that may restrict access to large bees such as bumble bees. Bumble bees could reach the nectaries with their long tongues, but I have not seen one attempt this. Every visiting insect has a different approach and objective while visiting the flowers, some affect the rate of the flower development process and others get away with feeding on nectar without aiding in cross-pollination.

Filament bases surround the nectar-producing disc at the bottom of the style. When harebell anthers release pollen, the tube formed by the filaments around the style traps pollen. As the style elongates, the pollen collecting hairs on the style push the pollen upwards, exposing the pollen to pollinators.

The pollen collecting hairs are stimulated by visiting insects, more stimulation with pollen feeding, and less with nectar feeding. The more the hairs are stimulated, the shorter the duration of the male phase. Hairs retract causing the remaining pollen to fall out of the nodding flower. The female phase then begins with the separation of the stigma. This process, accelerated by pollinators, ensures cross-pollination of the flowers.

Leafcutter Bees ~ Megachile spp.
Leafcutter bees are frequent visitors of harebell feeding on nectar. Their pollen-collecting hairs (scopa) on the underside on their abdomens come into contact with the pollen held on the style.

Digger Bees ~ Anthophora spp.
Long tongues allow digger bees to reach the nectar at the base of the style and avoid contact with pollen on the style. The flower in this image has released all the pollen, the filaments are drying up and the stigma is preparing to separate to receive pollen.

Green Sweat Bees ~ Agapostemon spp.
Green sweat bees visit harebell flowers for nectar. This bee is holding itself in the nodding flower by grasping onto the base of the style. The stigmas have separated and are ready to receive pollen transferred from visiting insects.

Small Carpenter Bees ~ Ceratina spp.
Small carpenter bees are some of the early visitors of harebell flower development. After the style elongates and the pollen collecting hairs are covered with pollen, small carpenter bees visit and feed on and collect pollen stuck stigma.











References
Attracting Native Pollinators: The Xerces Society Guide, Protecting North America's Bees and Butterflies

The Pollen-Collecting Hairs of Campanula (Campanulaceae). II. Function and Adaptive Significance in Relation to Pollination. Yvonne Nyman. American Journal of Botany , Vol. 80, No. 12 (Dec., 1993), pp. 1437-1443

Ohio Spiderwort Insect Visitors

Ohio Spiderwort ~ Tradescantia ohiensis

Ohio Spiderwort flowers open in the mornings for insect visitors, then close up during the heat of the day. The attractive blue to purple flowers have a fuzzy appearance due to the fine hairs on the filaments. Spiderwort flowers from late April through to July.

Bees are the primary visitor, for the abundant pollen in particular. Bumble Bees such as Bombus bimaculatus pictured here collect pollen to provision their nests.

Another common spring occurring bee is the Mason Bee (Osmia sp.), their hairy, blue metallic bodies make them fairly easy to identify.

Mason Bees build nests in cavities, they are the primary nester in bee boards in our area.

Small Carpenter Bees (Ceratina sp.) feed on the pollen of Ohio Spiderwort. They nest in hollow or pithy stems.

A great reason to leave dead, pithy branches such as Elderberry in your landscape to provide nesting habitat for this small bee.

Small Sweat Bees (Lasioglossum sp.) also like the pollen of Ohio Spiderwort. We have a lot of Small Sweat Bees in our landscape, probably because our soils are sandy which is where this ground nesting bee likes to excavate its nests.

Larger Sweat Bees such as this Green Sweat Bee (Agapostemon sp.) are brightly colored and hard to miss. They also nest in the ground.

These are one of the more difficult bee species to photograph, they're fast-moving and not as willing to stay in one place for very long.

The one type of bee that doesn't visit Ohio Spiderwort flowers for pollen is the European Wool Carder Bee (Anthidium manicatum). An introduced species from Europe, females like to visit Ohio Spiderwort for the fine hairs on the buds and flower stalks. Females chew the hairs with their sharp mouthparts, and use the 'wool' to make brood cells.

Syrphid Flies of many types will visit flowers and feed on pollen.

Also look for Bee Flies investigating the flowers.

And where there are bees, there are predators about such as this crab spider, legs outstretched waiting for the unsuspecting bee to stop by.

Ohio Spiderwort is a very adaptable prairie native of medium to dry soils, in full to part sun. It's a great early spring source of pollen for our native pollinators.

Native Plant of the Week: Nodding Onion ~ Allium cernuum

Nodding Onion ~ Allium cernuum


With our ongoing drought in many parts of the continent, it's a good idea to investigate what native plants are thriving in this heat. Nodding Onion is one of these natives, loving hot, sunny locations in dry sandy soils. It is also apparently tolerant of loam or clay soils.

Very similar to Prairie Onion (Allium stellatum), Nodding Onion has drooping umbel flowerheads comprised of 6 parted light pink flowers. Flower stalk heights range from 12 -24 inches.

The basal leaves are linear and grass-like in appearance, and often go unnoticed because the foliage of neighboring plants will hide the onion leaves.

The leaves have an onion odor, not as strong as chives but quite apparent. Nodding onion works really well intermixed with shorter prairie natives at the edge of a planting. It looks fantastic planted with Wild Petunia, Side Oats Grama and Spotted Beebalm all of which flower at the same time.

The primary visitor to the tiny flowers are small Halictid bees. Look for them clinging to the underside of the nodding flowers.

The occasional Leafcutter Bee will also visit the flowers of the Nodding Onion in our yard.

And where the bees visit, you will often find Tumbling Flower Beetles feeding on pollen.

I also spotted the Weevil species this morning. I'm going to investigate later if the weevil is feeding on any part of the Nodding Onion plant.

Nodding Onion is native to many parts of North America, see map below for range.

Kartesz, J.T., The Biota of North America Program (BONAP).
2011. North American Plant Atlas. Chapel Hill, N.C.

Native Plant of the Week: Tall Meadow Rue ~ Thalictrum dasycarpum

Tall Meadow Rue ~ Thalictrum dasycarpum


The Tall Meadow Rue is especially tall this year in our landscape with all the rainfall we've had - almost 6 feet in height. It typically reaches heights of 3 to 5 feet. A native perennial of medium to moist locations in full sun.

The flower clusters are very showy and branched. Individual plants are either have male or female flowers. The male flowers have showy dangling filaments with yellow anthers.

Tall Meadow Rue is very common in Minnesota, growing in low lying, moist, sunny areas next to wetlands or riparian habitats. Meadow Rue is rhizomatous so it often forms small clusters.

Small Sweat Bees are attracted to the staminate flowers and collect the pollen. The female flowers do not produce any nectar reward.

The Long Horned Beetle (Euderces picipes) seems to also feed on the pollen.

And another showing of the Sphegina fly, a fly who is attracted to white-flowering woodland natives. I've also seen this fly on Long Styled Sweet Cicely and Goat's Beard.

If you have a spot with moist, loamy or sandy soils in full sun, Tall Meadow Rue is an excellent candidate.

Tall Meadow Rue is native to central North America. See map below for range.

Kartesz, J.T., The Biota of North America Program (BONAP).
2011. North American Plant Atlas. Chapel Hill, N.C.

Native Plant of the Week: Beard Tongue ~ Penstemon digitalis

Beard Tongue ~ Penstemon digitalis


Beard Tongue is one of the showier native Penstemon with large white flowers arranged in a large cluster. An easy to grow native perennial, it is very adaptable to sandy soils as well and more loamy locations.

It can range from 18" to 48" in height. With an upright, sturdy habit that works well in both traditional perennial borders or naturalized plantings.

The basal leaves have short stalks, but the opposite leaves on the flower stem do not which gives Beard Tongue a nice form and highlights the large flower clusters.

The white flowers, sometimes with purple stripes, are 5 parted and tubular. The opening on this Penstemon is quite large so both bumble bees and tiny sweat bees can get their bodies inside. The flower has a flat base which makes a nice landing pad for pollinators.

Penstemon is derived from thee Greek word pente = 5, and stemon = stamen, meaning 5 stamens. Only 4 of the 5 stamens are fertile. (Wildflowers of Wisconsin)

When the flowers open, the anthers develop first. The anthers brush against the thorax or upper backs of bees as they visit the flowers. This action releases the pollen.

The style develops later and in doing so lowers its stigma downwards to prevent bees from entering the flower.

This tiny sweat bee is a regular visitor to the Beard Tongue flowers.

Bumble Bees also visit the flowers. Their larger bodies appear to get stuck in the flower tube as the use their long tongues to reach the nectar.

Leaf cutting bees also like the Beard Tongue flowers. They collect pollen on their abdomens.

Beard Tongue thrives in full or partial sun and mesic, loamy soils. It does reseed around the parent plant.

Kartesz, J.T., The Biota of North America Program (BONAP).
2011. North American Plant Atlas. Chapel Hill, N.C.

Beard Tongue is native to eastern North America. Some references indicate that it has possibly naturalized and not originally native to the upper midwest states such as Wisconsin and Minnesota.

Wafer Ash Insect Visitors

Wafer Ash ~ Ptelea trifoliata

Our small Wafer Ash flowered this year and I was surprised at how fragrant the flowers were. And it's no surprise that the fragrance attracted many types of pollen and nectar seeking insects.

The tiny four or five parted flowers are arranged in loose cluster about two inches in width.

Read an earlier post about Wafer Ash.

Muscid flies were enjoying the flower offerings, who knew that they have a taste for sweet smelling things too?

And Syrpid flies also were frequent visitors.

Tiny Sweat Bees (Lasioglossum species) were busy collecting pollen and nectar. It was no surprise that two types of Cuckoo Bees, both cleptoparasites were nectaring on the flowers too.

Here a Nomada species with its rusty brown coloration and yellow spots on its back. I featured this Cuckoo Bee in an earlier post this spring titled It's a Bee Eat Bee World.

Cleptoparasitic bees don't fashion their own nests but instead lay their eggs in nests of other ground dwelling bee species.

This Sphecodes species was a new sighting for me, very distinctive with its bright red body. It was also enjoying the nectar offered from the Wafer Ash. Neither of these Cuckoo Bees forage for pollen because they're not building their own nests.

What's fascinating about the Sphecodes bee, is that is belongs to the insect Family Halictidae (Sweat Bees) not the cleptoparasitic subfamily of Nomadinae (Cuckoo Bees).

The Sphecodes are parasites of the Sweat Bees, the same family in which they belong. Depending upon their social relationship to the host species, they can be cleptoparasites or just social parasites.

Cleptoparasites - Seek and Destroy
"A female of the solitary Sphecodes enters the nests of other solitary bees to lay an egg while the host female is away foraging. Once in the nest, although most other cleptoparasites do not harm the host's egg, a female Sphecodes destroys the host's egg before laying her own." (Attracting Native Pollinators)

Social Parasites - Coup d'Etat
If they're social parasites, they "enter the nest and in some way replace the queen, so that the host workers then tend and rear Sphecodes offspring." (Attracting Native Pollinators)