How Flowering Plants Attract Pollinators

With spring’s arrival, many of us marvel at the incredible diversity of beautiful blossoms that appear in the landscape around us. This stunning display becomes even more fascinating when we discover the intricate connections between flowering plants, or angiosperms, and the pollinators who visit them. Their mutually beneficial relationship is one example of Mother Nature’s extraordinary partnerships.

What is pollination?

All flowering plants rely on pollination, the transfer of pollen grains from the anther at the top of a stamen (male flower part) to the stigma at the top of a pistil (female flower part). This process of pollination leads to the development of seeds and fruit for plant reproduction, which helps ensure the survival of a species.

Female pistil with stigma at top, surrounded by male stamens and anthers. Photo by Melissa King

Some plants rely on self-pollination, defined as the abiotic transfer of pollen on the same plant without the involvement of any living organism. This inorganic process that does not include animals decreases genetic diversity, an important aspect of the adaptability of a species. However, the vast majority of angiosperms rely on cross-pollination, which includes a vector such as an animal, wind, or water to move pollen from one flower to another flower of the same plant species. The biotic, or biological, process that involves animals transferring pollen from one flower to another is an ecological survival strategy that increases genetic diversity.

It turns out that animals are responsible for approximately 80% of all plant pollination and 75% of the pollination of basic food crops for humans. Furthermore, one of every three bites of our food depends on the work of animal pollinators. These important helpers include bees, butterflies, moths, beetles, flies, birds, and bats, with insect pollinators, especially bees, responsible for most of the cross-pollination of flowering plants.

Butterfly holding onto flower as it probes for a sweet drink. Photo from Pixabay

“Our future flies on the wings of pollinators.” (quote from North American Pollinator Protection Campaign, US Forest Service)

Co-Evolution of Plants and Pollinators

The successful interaction of flowering plants and pollinators is due to ingenious morphological adaptations that have occurred over a long period of time. These plants and their pollinators depend on each other and have co-evolved in unique ways to enhance their mutualistic relationship.

Here is how it works: Flowers exhibit certain traits, such as visual cues, to attract certain types of pollinators. When pollinators visit these flowers, they get the energy-rich nectar and protein-rich pollen that they need to stay alive. In addition, angiosperms that depend on animal vectors produce pollen that is barbed and rather sticky, to facilitate hitching a ride from flower to flower. Moreover, to reduce competition for visits from valuable pollinators, angiosperms flower at different times of the year, thus producing continuous food resources for pollinators.

Pollinator Syndromes

In conjunction with these clever interactions, specific flower characteristics are associated with various types of pollinators. These floral strategies, such as shape, scent, and color, are referred to as “pollinator syndromes.” Based on the typical traits of certain flowers, scientists can predict which pollinators will be attracted to them.

Bee collecting pollen on purple flower. Photo: pexels.com

Butterfly using proboscis to sip nectar from orange flower. Photo from Pixabay

Visual cues are one way that angiosperms send signals to invite pollinators into their flowers. Certain colors make flower petals and sepals more noticeable, but which critters will be attracted to a particular color varies. Bees, whose color vision is acute and highly sensitive, respond to bright white, blue, purple, and ultraviolet light, but beetles prefer white or green. Butterflies, which can detect millions of colors with their compound eyes and multiple photoreceptors, respond to bright red, orange, pink, and purple. Conversely, moths like dull red, pink, purple, and white. Birds are attracted to red, orange, scarlet, and white, while hummingbirds especially like red and pink flowers. Bats, who are active at night, prefer white, light-colored flowers that bloom in the dark.

Nectar guide that directs insects toward the center of the flower. Photo from Pixabay

Many flowers exhibit distinct visual patterns with colorful lines or dots on their petals that direct animal pollinators to come right inside their flowers. Like an effective advertisement, these nectar guides help pollinators locate desirable nectar and pollen, making the pollination process much more efficient. Some flowers that attract bees, who see a different spectrum of light than we do, display an area of ultraviolet light in the middle of every petal, coupled with an area of low ultraviolet reflectance near the base of each petal. Although not visible to the human eye, bees can detect this combination of light patterns that creates a bullseye guiding them to the flower’s center. Once there, they feast on sweet nectar and collect dusty pollen.

Hummingbird sipping flower nectar with its slender beak. Photo by Raul Salvo on pexels.com

Flower shape and size are additional attributes that demonstrate how specialized plant morphology can attract and accommodate the physical structure of specific animal pollinators. For example, beetles need large, somewhat flat, open flowers to crawl around on as they seek food, whereas butterflies require narrow, tubular shapes that allow them to sip sweet nectar with their long proboscis. Bees and flies, with their small mouthpieces, like shallow flowers that offer landing pads, while birds look for larger flowers that are shaped like cups.

Scent is another trait associated with specific plant-pollinator partnerships. Bees and butterflies like pleasant, fresh scents, while bats prefer strong, musty odors. Moths are attracted to strong, sweet smells that emerge after dark, and flies like rotten, foul-smelling odors.

Mimicry is an unusual strategy that also helps lure pollinators to flowers. Several orchid species have flowers that closely resemble female insects, and as a result, male insects of the same type are attracted to these flowers. While there they try to mate, gathering pollen during the process and carrying it to another flower.

Pollen on bee’s fuzzy body as it enjoys sweet nectar from a flower. Photo from Pixabay

How can you help?

Pollinators are an essential element of earth’s ecosystems. Without them, most food crops and many other plant-based products would not be possible. It is estimated that the value of pollination on a global scale is worth more than $3 trillion. As conscientious gardeners who care about the natural world, we can take a leading role in supporting pollinators, to help them survive and thrive for years to come. Consider the following action steps:

Bee sipping nectar on cup-shaped flower. Photo from Pixabay

*Plant a diverse collection of native flowering plants in your own yard to provide habitats and food resources for native pollinators.

*Include wildflowers that bloom at different times of the year in your plant collection to provide a steady supply of food for pollinators.

*Reduce or avoid the use of hybrid flowers that may have altered colors and color patterns, shapes, or scents, which might fail to offer features that attract pollinators.

*Research host plants for specific types of native butterflies and make space for them in your gardens.

*Keep a few dead trees or fallen branches on your property as nesting sites for bees.

*If possible, steer clear of pesticides and don’t use them in daytime when pollinators are active.

*Share with others your knowledge about pollinators and their partnership with flowering plants.

Now that you understand more about the mutually beneficial relationship between angiosperms and pollinators, “Make your home their home.”