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

Plan Now for Spring Pollinators

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.

Wild Lupine Insect Visitors

Wild Lupine ~ Lupinus perennis 

Wild Lupine is a native perennial of dry, sandy sites in full sun. Flowering from late April/early May into June, the flower color ranges from light blue to dark purple.

Because of its early flowering time, overwintering queen Bumble Bees or their female offspring will visit the flowers. The irregular flower form means that the larger Bumble Bees don't have too much difficulty prying open the lower wing petals to reveal the reward inside.

Bombus auricomis

According to Illinois Wildflowers, there is no nectar reward provided by Wild Lupine, and pollen is forcibly ejected into the faces of bees.

Butterflies and moths will visit the flowers looking for nectar but come away with no reward. I photographed this Hummingbird Clearwing Moth this spring on our Wild Lupine flowers.

I also observed many Mason Bees (Osmia spp.) visiting Wild Lupine flowers this spring. They start with their rear legs prying open the petals, get a start on it opening, then use their mid and forelegs to hold the flowers open.

Wild Lupine and Mason Bees were built for each other, as Mason Bees collect pollen on their abdomens. Perfect for where the fused stamens are located just above the bottom keel, rubbing off some pollen for cross-pollination onto the Mason Bee abdomen.

Look for Mining Bees (Andrena spp.) a ground nesting native bee that emerges in early spring and visits flowers to collect pollen and nectar for nest provisioning.

Small Carpenter Bees (Ceratina spp.) also look in vain for nectar on flowers that have been forced open and are accessible as they cannot pry open the petals themselves.

Wild Lupine is a larval host plant to several butterfly and moth species, the most notable is the specialist Karner Blue Butterfly (Lycaeides melissa) an endangered butterfly.

Native Bee Spotlight: Mason Bees ~ Osmia spp.

Mason Bees ~ Osmia spp.

Mason Bees were one of the first native bees we knew were nesting in our landscape because we provided bee boards for them. They will nest in many types of natural cavities such as under rocks, behind bark or in the pithy stems of plants.

Mason Bees are a small to medium sized bee, with a blue/green metallic body which is moderately hairy.

There are many types of cavity nests that you can create, simply drilling holes in an untreated wood block and hanging it in a sunny location works well.

We started with some holes drilled in the end of a 2x4 board (maximizing the hole depth). For the first couple of years, we had a lot of Mason Bee activity.

We have since made simple wood holders out of plywood that are stuffed with hollow plant stems (Cup Plant, Pale Indian Plantain). Stems can be changed out every two years (after the adult bees emerge in spring). This ensures that you are providing clean nesting cavities.

Females collect pollen and nectar, combine the two ingredients forming a bee bread. They deposit the bee bread at the back of the cavity, lay a single egg on it where the larva will develop and consume the bee bread. She repeats the process of depositing bee bread in the cavity, walling off each section creating separate brood compartments.

We start to see these bees active in early spring, visiting Wild Geranium (Geranium maculatum) flowers in May. Females collect pollen on their abdomen as illustrated in this photo.

They also love our American Plum (Prunus americana) tree which is extremely fragrant and a great pollinator plant.

Mason Bees are being used as alternative pollinators of commercial crops. They have been fairly successful in filling voids left by honey bees for almond tree pollination in California.

These medium sized bees seem surprisingly strong, able to pry open the Wild Lupine (Lupinus perennis) flowers to access the rewards offered.

We see the last adults in early June visiting the Ohio Spiderwort (Tradescantia ohiensis) flowers.

There's lots of resources online on how to build Mason Bee houses, and some very creative examples.

A Mason Bee house is a great holiday gift idea for the wildlife gardener.







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

Native Plant of the Week: Wild Lupine ~ Lupinus perennis

Wild Lupine ~ Lupinus perennis


Wild Lupine is in full bloom in our yard right now. This native Lupine is smaller than the non-native, naturalized Large-Leaved Lupine (Lupinus polyphyllus), reaching heights of around 14 inches in our dry, sandy soil.

The palmately divided leaves are very attractive in their own right, offering a wonderful contrast to other native perennial foliage.

This is a great native for hot, dry sites and poor soils. Plant near the front or edge of your landscape so you can observe and enjoy all the different types of pollinators that visit the flowers.

Two species of Bumble Bees were visiting the flowers this week. Their large size makes nectaring on the flower a bit challenging, but their advantage over the smaller bees is they can easily pry apart the petals to reach inside the flowers.

The smaller Mason Bees (Osmia species) pry open the flowers with their rear legs, then use all six to keep it open so they can reach further inside the flower.

Mining Bees (Andrena species) also like visiting Wild Lupine flowers.

I also spotted a day flying Clearwing moth visiting the flowers. They will hover like Hummingbirds unfurling their long proboscis and inserting it into the flowers. With this sophisticated technique, there's no need for them to pry open the flowers.

Seeds form in hairy pods that are held upright on the stem. This is an easy plant to propagate from seed, cold stratify in moist sand in the fridge over the winter and scarify (scratch) the seed coat before planting in the spring.

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

Wild Lupine is native to eastern North America. See map for range.