An online resource based on the award-winning nature guide

Pollination

Witch Hazel Flowering and Dispersing Last Year’s Seeds

10-11-13  witch hazel flower and fruits 055Witch Hazel (Hamamelis virginiana) is nature’s final fanfare of the fall. As colorful fall foliage disappears, the yellow strap-like petals of Witch Hazel’s fragrant flowers brighten denuded woods. These flowers are pollinated by moths that are still active this late in the season, and develop into small, hard capsules that remain dormant throughout the winter. During the following summer, these capsules develop to the point where they expel two shiny black seeds 10 to 20 feet away from the tree. The seeds take another year to germinate, making the length of time from flowering to germination approximately two years. (In photo, the yellowish-tan capsules were formed this summer, and the one brown, year-old capsule has opened and dispersed its seeds.)

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Jewelweed’s Cross-pollination Strategy

10-1-13 bumblebee and jewelweed  092Jewelweed (Impatiens pallida), also known as Touch-Me-Not due to the sensitivity of its bursting seed pods, illustrates a strategy used by many flowers to promote cross-pollination. The male and female parts of the flower develop sequentially — first the male (stamen), then the female (pistil), so that they are not mature and receptive at the same time. The bumblebee in this photograph is squeezing into the spur of a Jewelweed flower in order to reach the sweet nectar it contains. In doing so, its back brushes against the strategically located, pollen-laden anther (tip of male stamen). When the bee enters another Jewelweed flower, if its pistil is mature, some of this pollen is likely to brush against the stigma (sticky tip of the female pistil), thereby cross-pollinating the flower.

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Did you know…

9-20-13  milkweed-did you know2 022Only two percent of Common Milkweed, Asclepias syriaca, flowers develop into pods, and all the seeds in a pod come from a single flower.


Bottle Gentian Flowering

9-10-13 bottle gentian IMG_8093Bottle Gentian, Gentiana andrewsii, is one of our latest blooming wildflowers, and one of our most beautiful. Because its petals are closed so tightly, only bumblebees (pictured) and a few other insects have the strength to push their way inside the flower to reach Bottle Gentian’s sugar-laden nectar.

Like many other flowers, Bottle Gentian times the maturation of its reproductive parts to discourage self-pollination. Male pollen-bearing stamens mature first, and by the time the female pistil is mature, the stamens have gone by so the flower’s pistil can’t receive its own pollen (see central pistil surrounded by withered stamens in insert).

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Goldenrod Pollen

9-4-13 goldenrod pollen 305Goldenrod is an extremely important foraging plant for honeybees in the late summer, when its flowers produce prolific amounts of nectar and protein-rich pollen. Goldenrod pollen, the orange lump that you see packed into the pollen basket (after being mixed with saliva) on the hind leg of this honeybee, is often blamed for the allergies that many people experience in the late summer and early fall. It is falsely accused, however, as ragweed pollen is the real culprit. Being wind pollinated, ragweed has light, fluffy pollen, which is easily dispersed (and easily enters nostrils). Goldenrod pollen is large and sticky, allowing visiting insects to gather it (intentionally as well as unintentionally) all over their bodies and transfer it to other goldenrod flowers, therein cross-pollinating them.

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Helleborine Drugs Its Visitors

7-29-13 helleborine 029Helleborine (Epipactis helleborine) is a common woodland plant which is easily overlooked due to its inconspicuous, small, greenish-purple flowers. However, this modest member of the Orchid family brings pollination to a new level. Its structure is said to not be morphologically attractive to insects, so Helleborine has come up with another strategy to get its flowers pollinated. It produces nectar that contains several chemicals, including oxycodone, a drug which has a morphine-like effect on organisms that ingest it. When insects drink the oxycodone-laced nectar, they become sluggish, which prolongs the amount of time they spend at the flower, which, in turn, increases the chances that the flower will be pollinated.


Chicory Pollinators

7-19-13 chicory pollenTwenty minutes of observing air-borne visitors to a patch of roadside Chicory revealed nine different species of pollinators, including bees, flies and beetles. Most of the insects were bees, which makes sense, as honeybees, leafcutting bees and ground-nesting bees are the primary pollinators of this flower. Without exception, all of the pollinating insects were covered from head to toe with Chicory’s white pollen grains. As they circled the flowers’ stamens collecting pollen, the insects’ bodies were inadvertently dusted with some of it. Thanks to these diligent pollen-collectors and transporters, American Goldfinches and other seed-eating birds will be feeding on Chicory seeds come winter. (Electron microscopy by Igor Siwanowic and Scienceworks.)


Canada Lily Pollinator

r-b hummingbird at Canada lilies 600A commonly held belief is that in order to be cross-pollinated, flowers have evolved to attract certain pollinators, including wind, mammals, birds and insects. These traits, or “pollination syndromes,” include the flower shape, color, odor, amount of nectar and flowering time. Flowers attractive to hummingbirds tend to be large, tubular-shaped and colored red, orange (or sometimes yellow). These flowers usually have a large supply of dilute nectar, which they secrete during the day. Since birds do not have a strong response to scent, the flowers they visit tend to be odorless.

Canada Lilies, found throughout eastern North America, have a distinct tubular shape, which appeals to Ruby-throated Hummingbirds. Their long, thin beak allows these birds to reach nectar at the base of the flower that is inaccessible to many other creatures. In order to reach the nectar, the hummingbird must enter the flower far enough so that its neck and breast press up against the orange pollen-laden anthers of the Canada Lily. When the hummingbird moves on to the next Canada Lily flower, it is very likely that some of this pollen will end up on the flower’s female structure, or stigma, thereby pollinating the flower. (Note that the stigma, in the center of the flower, is taller than the anthers, thereby discouraging self-pollination.)


Partridgeberry Flowering

7-9-13 partridgeberrey flowers2 IMG_1018In many areas the forest floor is now carpeted with flowering Partridgeberry (Mitchella repens), the creeping, woody vine found in both deciduous and coniferous woods. The pairs of white flowers occur in two forms. In the first form (pictured) the pistil is short and the stamens are long; in the second form the pistil is long and the stamens are short. This structure prevents each flower from fertilizing itself. Both flowers must be pollinated to obtain a single scarlet berry. Each berry is the result of the fusion of each ovary of the pollinated pair of white flowers. As such, each berry has two bright red spots on its surface.


Pink Lady’s Slippers Flowering

pink lady's slipper2   223Pink Lady’s Slippers (Cypripedium acaule), also known as Moccasin Flowers, differ from Yellow and Showy Lady’s Slippers in two fairly obvious ways. One is that the stalk the single flower is borne on bears no leaves. In addition, the pouch, or labellum, has a vertical slit running the length of it, rather than an oval opening on the top. Bumblebees are the only insect strong enough to push their way through this slit and are their main pollinators. In New England, almost 25% of the Pink Lady’s Slipper population have white flowers (see insert).


Yellow Lady’s Slipper Flowering

5-30-13 yellow lady's slipper 063There are only about three short weeks in the late spring when the blossoms of Yellow Lady’s Slippers grace our woodlands and wetlands. The production of an orchid is a complicated process. If pollination and fertilization are successful, hundreds of thousands of some of the smallest seeds of any flowers are scattered by the wind. The seeds of Yellow Lady’s Slippers (and other orchids), unlike those of most flowering plants, contain no food for the seedling plant. In addition, the coating surrounding the seed is extremely tough, so much so that the seed can’t germinate until Rhizoctonia fungi digest the outer coating, which allows the inner seed to access soil nutrients. This can take two years or more and then it may take another few years for the plant to produce a flower.


Wild Columbine & Ruby-throated Hummingbirds

5-16-13 wild columbine158Wild Columbine (Aquilegia canadensis) is in full flower, and its design and color beckon to a recently-returned migrant that is attracted to red as well as tubular flowers – the Ruby-throated Hummingbird. Not only does the flowering of Wild Columbine coincide with the arrival of hummingbirds in May, but the ranges of these two species are much the same. Wild Columbine’s five petals are in the shape of spurs, the tips of which contain nectar. Only hummingbirds and long-tongued bees can reach the nectar, and thus are its primary pollinators (there is a short-tongued bumblebee that tears open the tip of the spur in order to reach the nectar). While the hummingbird hovers beneath the flower and drinks nectar, its head rubs against Columbine’s long anthers, and the resulting pollen on the hummingbird’s head is brushed off onto the long styles of the next (Columbine) flower it visits, thereby pollinating it.


Early Saxifrage Flowering

5-8-13 early saxifrage153Early saxifrage (Micranthes virginiensis) is well named – it flowers early in the spring, and is often found growing in or on rocks. (The name saxifrage derives from the Latin words “saxum” meaning rock and “frangere,” to break. When the small seeds of saxifrage lodge in rock crevices and germinate, the plant looks as though it split the rock.) If you look closely you’ll see that early saxifrage’s flower stalk has many hairs – they are glandular and their stickiness is thought to deter ants from taking nectar from the flowers, so that it can attract more efficient pollinators.


Hepatica Blooming

4-18-13 hepatica DA8A9542Hepatica has finally opened its hairy buds and greeted the world with its beautiful white, pink, blue and lavender blossoms. Typically the only wildflowers to appear earlier than this member of the Buttercup family are skunk cabbage and coltsfoot. Like many flowers, hepatica blossoms open on sunny days, and close at night and on cloudy days. This prevents rain from washing out the pollen and nectar which help attract pollinating insects, including early-flying bees and flies.


A Great Christmas Present!

If you’re looking for a present for someone that will be used year round, year after year, Naturally Curious may just fit the bill.  A relative, a friend, your child’s school teacher – it’s the gift that keeps on giving to both young and old!

One reader wrote, “This is a unique book as far as I know. I have several naturalists’ books covering Vermont and the Northeast, and have seen nothing of this breadth, covered to this depth. So much interesting information about birds, amphibians, mammals, insects, plants. This would be useful to those in the mid-Atlantic, New York, and even wider geographic regions. The author gives a month-by-month look at what’s going on in the natural world, and so much of the information would simply be moved forward or back a month in other regions, but would still be relevant because of the wide overlap of species. Very readable. Couldn’t put it down. I consider myself pretty knowledgeable about the natural world, but there was much that was new to me in this book. I would have loved to have this to use as a text when I was teaching. Suitable for a wide range of ages.”

In a recent email to me a parent wrote, “Naturally Curious is our five year old’s unqualified f-a-v-o-r-I-t-e  book. He spends hours regularly returning to it to study it’s vivid pictures and have us read to him about all the different creatures. It is a ‘must have’ for any family with children living in New England…or for anyone that simply shares a love of the outdoors.”

I am a firm believer in fostering a love of nature in young children – the younger the better — but I admit that when I wrote Naturally Curious, I was writing it with adults in mind. It delights me no end to know that children don’t even need a grown-up middleman to enjoy it!


Bottle Gentian & Bumblebees

Bumblebees are nothing if not perseverant.  Prying Bottle Gentian’s (Gentiana andrewsii) petals open is a monumental task, and one that few insects, other than large species of bumblebees, attempt — much less accomplish.  The relationship of bumblebees and Bottle Gentian is an example of a mutualistic association — the bees benefit by having exclusive access to a bountiful and sugary nectar supply, and the plants benefit by attracting “loyal” pollinators that improve the chances for cross pollination.


Common Milkweed Pollination

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The structure of the Common Milkweed (Asclepias syriaca ) flower is such that its pollen, produced in two saddlebag-like sacs with a black appendage joining them, snaps onto an insect’s leg when the two come in contact with each other. To assure that the chances of this are high, the pollen sacs (pollinia) hang inside a slit that is located between each of the five cups, or hoods, that contain nectar. An insect lands on the slippery flower, attracted by both the scent and availability of nectar, and inadvertently one or more of its six legs slips down between the hoods into a slit, where the pollinia automatically attach to the leg. The insect withdraws the leg upon leaving to find more milkweed nectar, and the attached pollinia eventually falls off onto another milkweed flower, pollinating it. Unfortunately, about 5% of milkweed flowers visited trap insects because they cannot extract their legs from the slit. It is not uncommon to see an insect dangling from a Common Milkweed flower – during a 30 minute visit to a milkweed patch recently I released 2 flies, 3 skippers (butterflies) and one honeybee that were caught, but hadn’t yet perished.


Hummingbird Clearwing Moth

Of all the insects I’ve found in milkweed patches over the years, the Hummingbird Clearwing is one of my favorites. It is a species of sphinx moth, named for its habit of hovering at flowers while it gathers nectar with its proboscis in a manner similar to that of hummingbirds. In fact, they are often mistaken for hummingbirds. The transparent wings, light brown thorax and dark chestnut abdomen are the field marks to look for. A diurnal moth, the Hummingbird Clearwing can often be found during the day in milkweed patches.


Blue-eyed Grass

It’s easy to miss Blue-eyed Grass (Sisyrinchium angustifolium), as its flower is only about ½” in diameter and the plant only reaches a height of six to twelve inches. Blue-eyed Grass is a member of the Iris family, not, as its name implies, a member of the Grass family, although it does have stiff, grass-like leaves. Dark lines on its petals and sepals may well serve as nectar guides, leading pollinators to the yellow center. Each blossom is open for only a day at most. Typically you find Blue-eyed grass growing in sunny, wet fields, often on elevated soil — Thoreau noted that if you followed Blue-eyed Grass through a wet meadow, you could keep your feet dry.


Pitcher Plant Flowers

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The Pitcher Plant (Sarracenia purpurea) is a well-known carnivorous plant of bogs. It gets some of its nutrients by trapping and drowning prey in rain water that is caught inside a modified leaf that forms a cup. While most people are familiar with the leaves of Pitcher Plants, unless you visit a bog in June, you’re not likely to see their unique flower. It is curved over when it’s mature and its sepals (modified leaves that protect the bud and are located above the petals in these photographs) are red-purple and pointed; the petals are red and rounded. An approaching insect would be guided into the flower between two of the sepals–it would land on a petal and climb into the flower onto the umbrella-shaped stigma (the sticky top of the female pistil) which I inverted in one photograph in order to show the male pollen-producing stamens. An insect entering the flower would brush against the stamens, collecting pollen on its back while pollen from a previously-visited Pitcher Plant would fall off the insect onto the sticky stigma on which it was standing, pollinating the flower.


Fringed Polygala

Fringed Polygala (Polygala paucifolia) looks a bit like a miniature orchid, but it is not — it is in the Milkwort family. The structure of its ¾-inch bright magenta-pink blossoms is well-suited for its bumblebee pollinators.  The bee lands on the pink fringe at the front of the flower and its weight triggers the white “keel” to drop down.  A slit at the keel’s top opens, exposing the reproductive parts of the flower.  Pollen from the stamens is rubbed onto the bee’s hairs while it probes deeply into the base of the flower for nectar, while pollen from a previously visited Fringed Polygala is scraped off onto the stigma, where it needs to be in order for fertilization to take place.

 


Red-necked False Blister Beetle

 

If you find a blossoming Trout Lily in the woods it is quite likely that you will also find one of its most common pollinators, the Red-necked False Blister Beetle (Asclera ruficollis), on it. Ardent pollen eaters, this group of beetles obtain their common name because many species cause blisters when pinched or squashed against skin. Adults mate on flower heads during pollen feeding. Both sexes feed on pollen, which acts as an attractant, but the female will not accept the male until her gut is packed full of pollen. She stores the pollen in a special intestinal sack in which an enzyme causes the pollen to partially germinate — this causes the indigestible covering of the pollen grain to rupture. She then digests the contents of the pollen grain, which she uses to manufacture eggs. 


Spring Beauty Pollinators

Spring Beauty (Claytonia virginica) is one of our earliest woodland wildflowers to blossom, and thus an important source of nectar and pollen for the earliest foraging insects.  Pink lines (“bee guides”) on each of its five petals lead pollinators to the center of the flower, where the nectar is located. The pollinator in this image, Andrena erigeniae, is one of the more common species of bees that visits Spring Beauty in the early spring.  Notice the slightly pink pollen she has gathered into the pollen basket on her hind leg.  If you’re interested in spending time observing the series of different insect pollinators that visit Spring Beauty as the season progresses, there’s a golden opportunity for you.  If you go to http://springbeauties.wordpress.com/ you can participate as a citizen scientist volunteer and participate in their survey.


Beaked Hazel in Flower

Many shrubs really come into their own in the spring when they flower — not necessarily big, flashy flowers, but more subtle and delicate blossoms, with beautiful colors and designs.  Beaked Hazel (Corylus cornuta) is such a shrub. Its female flowers are now blooming – exquisite little maroon flowers with magenta highlights and pistils that curl this way and that in hopes of catching pollen.  One advantage to flowering before leaves are out is that there is less interference with pollen dispersal.  The entire flower is less than 1/4” in diameter.


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