Journal of the Oklahoma Native PlantSociety, Volume 3, Number 1, December 2003


Oklahoma Native Plant Record 73
Volume 3, Number 1, December 2003

Caddell, G. M.
https://doi.org/10.22488/okstate.17.100024

Critic’s Choice Essay

Take time to watch, not just smell the wildflowers!
Gloria M. Caddell

     Although plant-pollinator interactions
between orchids and bees in the tropics may
seem more interesting than those closer to
home, Oklahoma is full of fascinating plant-
pollinator interactions and mechanisms.
The most important pollination agents in
Oklahoma are wind and insects.  Wind is
particularly effective where many plants of
the same species grow close together.
Prairie grasses, and dominant trees of our
forests and woodlands, e.g. post oak and
blackjack oak, are wind-pollinated.  There
are few things more beautiful than anthers
dangling from a grass spikelet along with
feathery stigmas that trap wind-borne
pollen!   In spring, male flowers of oaks are
borne on pendulous catkins, releasing pollen
that catches on stigmas of tiny female
flowers held close to the branch.
     Insects are major pollinators of our
prairie forbs, and their flowers are visited by
a variety of insects, including butterflies,
moths, beetles, flies, bees, and wasps.  Of
these, bees are most important.  You can
observe bumblebees with glistening,
saddlebag-shaped pollinia of green
milkweed (Asclepias viridis) on their legs.
You can hear their buzzing as bees clasp the
anther cone of western horsenettle (Solanum
dimidiatum) and use their flight muscles to
vibrate pollen out through pores at the top of
the anthers.
      Flower characters such as color, shape,
size, and amount of nectar can sometimes be
used to predict major pollinator(s) of a
species.  But it takes many hours of
observing and collecting insect visitors to
see if they are carrying pollen, to determine
which are actual pollinators.  My students
and I have observed over 20 families of
insect visitors to a single species, but find
that only two or three effectively transfer
pollen.
     Differences in flowers among species are
often clearly related to pollination, but

differences among flowers within a single
species may also be related to pollination
and are equally intriguing. Within a
population you find sometimes subtle, and at
other times obvious, differences between
flowers at different stages.  For example,
when a pink gentian (Sabatia campestris)
flower opens its anthers are bright yellow
and release pollen, but its style branches are
green, coiled together, and lay flat against
the petals.  As the anthers wither the style
branches uncoil, become erect, turn bright
yellow, and their stigmas become receptive
to pollen.  In any population and even on the
same plant, you can find flowers with style
branches in various stages of uncoiling.
Difference in timing between pollen release
and stigma receptivity is a mechanism to
promote cross-pollination.  When flowers of
fog fruit (Phyla) open, they have a yellow
spot near the corolla tube opening (the
“throat”).   Later in the day the spot turns a
rosy-lavender color, less visible to bees.
Older flowers remain on the inflorescence as
new flowers open, but in many cases such as
this, newer, more attractive flowers offer a
greater reward, e.g. more nectar.
     In prairie bluet (Hedyotis nigricans)
some plants bear flowers with long styles
and short stamens. Others bear flowers with
short styles and long stamens with clearly
visible blue anthers. Insects that contact
anthers of long stamens will likely transfer
that pollen to a long-styled flower on
another plant. So this mechanism also
promotes cross-pollination.
      Details of flowering stages and plant-
pollinator interactions of many Oklahoma
plants have not been well-documented.  I
encourage you to stop, sit, and not only take
the time to “smell” the wildflowers, but to
watch them as well.  You will surely see
things that have never been observed before!

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