An online resource based on the award-winning nature guide

Pollination

Turtlehead Flowering & Being Pollinated By Bumble Bees

Turtlehead (Chelone glabra) can be found growing along stream banks and wetlands throughout eastern North America. This plant gets its common name from the flower’s long arching upper lip, or hood, which overlaps the lower lip like a turtle’s beak.

The male parts of the flower mature before the female parts, and when pollen is being produced these lips are very hard to pry open. Pollinators are primarily bumble bees, which are some of the only insects that have the strength to open the flower. When the female pistil matures, the lips relax a bit, so entry is easier. However, access to the nectar at the base of the flower is restricted (by a sterile stamen) to long-tongued insects. Thus, it is specifically long-tongued bumble bees that are able to both enter the flower and to reach the nectar. (Photo:  bumble bee collecting pollen (see filled baskets on hind legs) from Turtlehead)  Thanks to Jody Crosby for photo op.

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Cardinal Flower Blossoming

You can’t get much redder than the red of Cardinal Flowers.  Their petals act as brilliant red flags beckoning Ruby-throated Hummingbirds, who favor red, to come drink their nectar (and at the same time, pollinate them).  Because their chief pollinator has wings and the ability to hover as it drinks, Cardinal Flower has no need for a landing platform, which most insect-pollinated flowers have.

Cardinal Flower has both male and female flowers.  Above the red petals is a red tube, at the tip of which the reproductive parts of the flower emerge.  First to appear are the male flowers, displaying pollen-bearing stamens.  After they die, sticky, Y-shaped pistils extend from the flower, ready to receive pollen.  The female flowers thus follow the male flowers (protandry).  These flowers mature from the bottom to the top of the spike and you often see both male and female flowers on the same plant (just barely discernible in pictured flower spike).

Male flowers produce more nectar than female flowers, and hummingbirds seem to know this, as they spend most of their time at the youngest, and therefore male, flowers on the top half of the flower spike.

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Crab Spiders Active

4-29-19 crab spider on trailing arbutus_U1A7395Trailing Arbutus (Epigaea repens) is one of our earliest spring wildflowers. Sometime in April or May the creeping, leathery, evergreen leaves of this plant suddenly come alive with white or pink tubular flowers. While they are delightful to look at, their fragrance is what truly sets them apart from many other plants that flower this time of year.

Because there aren’t that many insects about this early, nor flowering plants, insect predators can have a challenging time finding prey. The pictured crab spider chose its perch wisely: bumble bees are the main pollinators of Trailing Arbutus, and queens are out scouting for food as they begin to establish their colonies.

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Indian Cucumber Root Flowering & Fruiting

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Indian Cucumber Root, Medeola virginiana, lives up to its name, as its rhizomes have a mild cucumber taste. Equally as enticing are its flowers — delicate and oh so intricate.

This member of the Lily family has one whorl of leaves if it isn’t going to flower (too young or without enough energy to reproduce), and two if it is. If there are two whorls of leaves, look under the top whorl and you will find flowers unlike any other you have seen. The pale petals fold back and from the center emerge three long reddish styles and several purple stamens (reproductive parts). Occasionally the flowers are above the topmost leaves, but typically they are below.

The change in position that Indian Cucumber Root flowers undergo as they develop into fruit is as fascinating as their appearance. The pedicels, or stalks, of these flowers become more erect once the flowers have been pollinated and fertilized, to the point where the dark blue berries mature above the upper whorl of leaves. You can see both stages in this photograph (styles have yet to fall off the developing fruits).

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Bottle Gentian Pollination

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Getting inside the flower of Bottle Gentian or Closed Gentian (Gentiana clausa), one of our latest flowering plants, in order to collect nectar and pollen is a monumental task that few insects, other than fairly large species of bumble bees, attempt. The petals are closed so tightly it takes even bumblebees several seconds of pushing, shoving and cramming to push the petals aside and get through the miniscule opening at the top of the blossom.

Pollen is the primary bumblebee attractant, as the sugar concentration of Bottle Gentian’s nectar is fairly low. Some bumble bees take a short cut – they chew a hole to gain access to the reproductive parts of the flower.  The hole is often two-thirds of the way up the blossom, directly opposite the pollen-laden anthers within the flower. Look closely at the hole in the lefthand blossom in the photograph and the adjacent, dissected blossom, and you will see that the bee’s aim was dead on.  You can even detect a portion of the anther through the hole.


Flight of the Bumblebee

bumblebee and turtlehead 049A4838If you examine plants that are still flowering this late in the season (such as asters, goldenrod and late-blooming turtlehead) early in the morning when it’s still quite cool or late in the day, many of the pollinators you see will be bumblebees, not honey bees. One reason for this is that they have different temperature tolerances for flight. You rarely see a honey bee when the temperature is below 57°F as they cannot fly when it is this cool. Bumblebees, however, are capable of flight when the air temperature is as low as 50°F.

Even so, bumblebees cannot take off unless their flight muscles are above 86°F; they maintain the temperature of their thorax (where wings and wing muscles are located) between 86°F and 104°F regardless of the ambient temperature. The way in which they raise the temperature of their thorax involves uncoupling their wing muscles so that the wings themselves do not move. They then use their wing muscles to shiver and raise the temperature of their thorax until it’s sufficiently warm enough for them to fly.

At rest a bumblebee’s body temperature will fall to that of its surroundings. If it is cool out, and the bumblebee wants to take flight, you can actually see its abdomen pumping to ventilate the flight muscles. An entomologist studying this phenomenon discovered that the rate of pumping can give an indication of the temperature of the bee. It ranges from around 1 pump per second when the bee is 86°F, to 6 pumps per second when it reaches 95°F.


Pruinose Squash Bees

8-17-17 pruinose squash bees2 049A2916The Pruinose Squash Bee (Peponapis pruinosa) is most often noticed when it’s gathering nectar or pollen from squash, pumpkin, watermelon or gourd blossoms.  (Squash bees have been shown to be excellent pollinators of zucchini and butternut squashes, among others. If numerous, they thoroughly pollinate all available flowers, rendering later visits of honeybees superfluous. Before Europeans brought honeybees to the New World, squash bees were busy aiding the adoption, domestication, spread, and production of squashes and gourds by indigenous peoples throughout the Americas.) The bee’s black and white striped abdomen is easy to recognize.

While female squash bees are busy foraging for pollen in the flowers of plants in the Cucurbitae family, male squash bees can be seen darting between flowers, searching for mates. By noon, they are fast asleep in the withered flowers.

Pruinose Squash Bees are solitary bees, with every female digging her own nest in the ground. These consist of vertical tunnels that end with a number of individual chambers that are a foot or two deep in the soil. Each chamber is provided with an egg and a lump of pollen so that when the egg hatches, food is readily available. (Photo: five Pruinose Squash Bees packed into a single Bindweed flower)