Guessing Pollination Strategy Based on Flower Power

Reprint from January 2018

Question:

Is there an easy way to tell if a flower is wind-pollinated or insect-pollinated?

- Leah M., Albuquerque

Answer:

This question is a good one because the answer is beautiful. Big, fragrant, flamboyant flowers are a good indicator that an insect or other animal pollinates the plant. When the flowers are tiny, lacking color, and inconspicuous and might be even be considered ugly, they are likely wind-pollinated. Vectors for pollination can be biotic (e.g., insects, bats, birds, humans) or abiotic (e.g., wind, water, self-pollination).

The flower scent, shape, and color and the timing of bloom can give clues to which insects are involved in pollination. Flowers that reek like dead flesh attract flies. Night-bloomers are often pollinated by nocturnal animals like moths and bats. Generally speaking, bee- and butterfly-pollinated species tend to have flowers with bright colors, nectaries (nectar-secreting glandular organs), and sweet scent.

Tubular flowers are perfect for animals with long noses or beaks. Dr. Ashley Bennett, former NMSU Extension Integrated Pest Management Specialist, added that some bees are short-tongued and others are long-tongued, which determines what flowers they visit for nectar and end up pollinating. For example, long-tongued bees can access nectar in very narrow, tubular-shaped flowers, like some penstemons, while short-tongued bees can’t reach the nectar in these flowers. Short-tongued bees need flowers that are shallow or disc-shaped like plants in the sunflower and mint families.

Like us, birds and butterflies see red, green, and blue as their visible spectrum. Many insects see green, blue, and various shades of ultraviolet. I recommend a quick Google image search “flowers in ultraviolet light.”

In its native habitat, the common houseplant Philodendron selloum can raise its own temperature 15 degrees to a hot-to-the-touch 114°F, and then maintain that exact temperature during the 2-day flowering period! You can guess why. Certain scarab beetles that prefer to mate at this temperature are attracted to the heat and end up covered in pollen ready for transport.

Female pecan flowers (left) are nowhere as big or beautiful or as heavily scented as a rose (right). This distinction offers a clue about the plants’ pollination strategies. Photo credits Marisa Thompson

When water is a pollination vector, the pollen floats along until it reaches the flower. This is called surface hydrophily and is relatively rare, perhaps more so here in New Mexico. Wind is not rare at all, as we all know too well. A good thing about wind—perhaps the only good thing—is how great it is at spreading pollen and fertilizing so many plants. Wind pollination is common in grasses and many tree species, such as pine and pecan. Do you know what color the petals of a pecan flower are? Most people haven’t ever seen a pecan flower before. And the petal question was a trick. Like many wind-pollinated species, pecan flowers lack petals completely, are unscented, and are a tad bit ugly. Think “fuzzy brown peppercorn.”

There are upsides and downsides to these different pollination strategies. Lots of precious energy goes into making the nectar and bright colors that attract pollinators, so only a moderate amount of pollen can be budgeted. However, if the right insect is targeted, they can transfer pollen grains very efficiently by taking the pollen directly to a flower that can be fertilized with it.

Wind-pollinated species that don’t need to attract pollinators can put all of that energy into making profuse amounts of pollen, which is critical because the wind doesn’t choose where the pollen lands.

Are there anomalies to this rule of thumb that showy flowers are pollinated with biotic vectors and boring flowers are abiotically pollinated? Probably. The only rule-breakers I can come up with are bougainvillea and poinsettia. Both of those super-showy, insect-pollinated plants developed a different strategy for attracting pollinators: the actual flowers are unremarkable, but their surrounding bracts (modified leaves just below the flower) are gorgeous and can hold their color much longer than petals ever could, so they actually follow the rules after all.

Visit our 25 years of NMSU Southwest Yard & Garden column archives.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

Links:

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