By Lisa Mason, Arapahoe County Extension
In general, research has shown that plants have specific
flower traits that attract pollinators, and the plants provide the pollinator
with nectar and pollen rewards. These attractive traits can include flower
color, odor, shape, and availability of pollen and nectar. Some plants even
have nectar guides which are markings showing where the pollinator should go to
collect the reward. Different traits will attract different pollinators. Why
would a plant evolve with traits to attract pollinators? Because visiting
pollinators will facilitate plant reproduction. This relationship benefits both
the plants and the pollinators.
For example, bird pollination is called “ornithophily.”
In Colorado, hummingbirds are primary
bird pollinators. We know that hummingbirds generally prefer to visit flowers
that are red, orange, or white. The flowers tend to be funnel-shaped, hang
loosely on the plant, and have plenty of nectar deep in the flowers. For other
birds around the world such as sunbirds, honeycreepers, and honeyeaters, the
plants tend to have strong perch support for the bird to land.
Flowers that attract birds typically don’t have an odor,
because birds don’t need the scent to find the flowers. You might also notice
that the flower petals tend to curve outward to make it easier for a hummingbird
in flight to drink nectar.
|A female broad-tailed hummingbird (Selasphorus platycercus). Note the
pollen on her head. Photo: Nancy Klasky|
The USDA Forest Service compiled a chart
of pollinator syndromes for the major groups of pollinators.
A wide variety of research is available demonstrating different
pollinator syndromes. I want to share two research studies with you.
of the Long-Spurred Orchid
In the 1860’s, Darwin studied orchids including the long-spurred
orchid, Angraecum sesquipedal. He predicted the flowers were pollinated by a long-tongued moth because
the flowers have a long spur approximately 12-inches long! The nectar sources are
located deep in those long spurs. When Darwin received a specimen of this
orchid, his wrote, “… good heavens what insect can suck it” (Darwin, 1862b).
At the time, no
pollinators had been observed pollinating these orchid flowers. Scientists
predicated pollinator could possibly be the species, Xanthopan morganii, and subspecies,
Xanthopan morganii praedicta, commonly called the Morgan’s sphinx moth
because they have a proboscis length (tongue-like tube) that averages over 8
inches long. More than 130 years later after Darwin’s prediction, documentation
of this moth pollinating the orchid was finally published beginning in 1993 (Arditti et al., 2012). To learn more, I recommend reading this journal article.
Pollinator Syndromes in Columbines
Another research example
that we see in Colorado shows that columbines (Aquilegia spp.) have
adapted and evolved to attract different pollinators depending on their spur
length. This is considered a “pollinator shift” when the plant adapts to the
traits of a pollinator (Whittall and Hodges, 2007).
|Besides the spur length, note the other traits the
columbines show to attract their designated pollinator. Image credit: Whittall and Hodges, 2007|
Your Garden and Pollinator Syndromes
With anything, there are always exceptions to the rules. If
you are looking to plant flowers to attract pollinators, you can use pollinator
syndromes as a general guideline, but we recommend doing additional research
and reading about pollinator-friendly plants that grow well in your area. For
instance, to support pollinators, avoid double flowers. Many double-flowered horticultural
varieties typically do not have pollen and nectar available for flower
Here are some resources for pollinator-friendly plant lists:
Pollinator Habitat: https://extension.colostate.edu/docs/pubs/insect/05616.pdf
Native Bees to Your Yard: https://extension.colostate.edu/docs/pubs/insect/05615.pdf
Butterflies to the Garden: https://extension.colostate.edu/docs/pubs/insect/05504.pdf
Low-Water Native Plants for Pollinators: https://conps.org/wp-content/uploads/2015/05/Low-Water-Native-Plants-for-Pollinators-brochure-6-8-15.pdf
Low-Water Native Plants for Colorado Gardens:
Mountains 7,500’ and Above: https://conps.org/wp-content/uploads/2017/08/Low-Water-Native-Plants-for-CO-Gardens-Mountains.pdf
Low-Water Native Plants for Colorado Gardens:
Front Range and Foothills: https://conps.org/wp-content/uploads/2017/08/Low-Water-Native-Plants-for-CO-Gardens-Front-Range-Foothills.pdf
Arditti, J., Elliott, J., Kitching, I. J., Wasserthall, L.
T. ‘Good Heavens what insect can suck it’ – Charles Darwin, Angraecum sesquipedale and Xanthopan
morganii praedicta. Botanical Journal of the Linnean Society
169, Issue 3, 403-432 (2012). https://doi.org/10.1111/j.1095-8339.2012.01250.x
Darwin CR 1862b. Letter 3411-Darwin, C. R., to Hooker, J.
D, 25 January 1862. Available at: http://www.darwinproject.ac.uk/entry-3411
J., Hodges, S. Pollinator shifts drive increasingly long nectar spurs in
columbine flowers. Nature 447, 706–709 (2007). https://doi.org/10.1038/nature05857