By Melissa Starkey
June is National Pollinator Month, so it’s a great time to talk about the wonderful creatures that provide this important service in our ecosystems. Pollination is the process of transferring pollen from the male anthers of a flower to the female stigma for fertilization to occur. The resulting fruits and seeds are the plants’ means of reproducing and are also important food sources for wildlife and humans. Read on to learn about the fascinating diversity of pollinators and the ways flowers have evolved to attract them.
Image 1: A butterfly visiting hollow-stem Joe-pye weed (Eutrochium fistulosum).
What is the first thing that comes to mind when you think of pollinators? Perhaps bees? While bees are certainly crucial pollinators, they are only part of the story. In fact, many other insects besides bees are also important pollinators. Wasps, flies, moths, butterflies, and beetles all pollinate flowers. If it weren’t for minute midges pollinating cacao plants (Theobroma cacao), we wouldn’t have chocolate! Likewise, if you’re a fan of figs, you have tiny wasps to thank for pollinating the plants that produce these fruits.
Pollination services aren’t just limited to insects, but birds, bats, and even lizards and some primates also do the job. Bats are the main pollinators of blue agave (Agave tequilana), which is used to make tequila. The plant’s flowers are receptive at night when bats are active and emit an odor of rotting fruit to attract them. More locally, hummingbirds are always a welcome sight in our gardens and pollinate many native wildflowers, especially those with long, tubular, red flowers such as cardinal flower (Lobelia cardinalis). Another hummingbird-pollinated plant, wild columbine (Aquilegia canadensis), blooms just in time to welcome these migrating birds back to the area in the spring.
Image 2: The red tubular flowers of wild columbine (Aquilegia canadensis) (A) and cardinal flower (Lobelia cardinalis) (B) attract hummingbirds.
With the large diversity of pollinators, plants have evolved various mechanisms to attract them to their flowers. Color, shape, scent, and bloom time all contribute to determining which pollinators flowers attract. Many garden favorites have pleasant scents and bright colors that are not only pleasing to humans but serve to draw in butterflies attracted by the sweet aroma and promise of nectar. Other plants have a very different strategy to attract their pollinators. What do you think a flower that smells like decaying meat is trying to lure in to pollinate it? If you guessed flies, that’s right! The common name for one such plant, the native Smilax herbacea is common carrionflower for a good reason — if you stumble across this plant on a hike, you surely won’t forget the scent! Other plants, like pawpaw (Asimina triloba), not only have a rotten scent, but its maroon flowers also look like meat to attract the flies beetles who pollinate it.
Image 3: Rotten smelling flowers of common carrionflower (Smilax herbacea) (A) and pawpaw (Asimina triloba) (B) attract flies for pollination.
Nectar is an enticing reward and important food source for many pollinators. Some flowers have long, tubular shapes where only animals with long tongues, such as bumblebees, butterflies, moths, and hummingbirds can easily access the nectar. These creatures end up getting pollen on their bodies while retrieving the nectar and pollinate the next flower of that species that they visit. Certain plants not only provide nectar, but also show pollinators exactly where to go to get it. Nectar guides are colored markings on petals that direct bees to their nectar reward inside the flower, similar to how lights on a runway guide a landing plane. You can clearly see nectar guides on flowers of foxglove (Penstemon species) and Carolina petunia (Ruellia caroliniensis), June bloomers here in the garden.
Image 3: Nectar guides on Dark Towers hybrid beardtongue (Penstemon ‘Dark Towers’) (A) and Carolina petunia (Ruellia caroliniensis) (B) point bees to their nectar reward.
Next time you’re walking around the garden, be on the lookout for different kinds of flowers and see if you can guess what pollinates them! Consider planting a pollinator garden of your own, with a diversity of plants to attract and support a variety of our wonderful pollinators.