Tamaracks, or American Larches (Larix laricina) are non-flowering plants (often found growing in bogs) that reproduce using seeds that are borne on the woody scales of cones. Conifers (Tamarack is one of about 20 deciduous conifers, but the only one in New England) have both male and female cones. The male cones produce pollen which is distributed by the wind and the female cones contain ovules which, when fertilized, develop seeds.
The male (pollen-bearing) cones look like little, round buttons (less than 1/5th of an inch wide), and consist of brown to yellowish pollen sacs with papery scales at their base. After maturing in early spring, they shed their pollen and then wither. The female cones of Tamarack are also small – less than ½ inch – and initially resemble tiny, maroon roses. As in all conifers, the scales open temporarily to receive pollen, then close during fertilization and maturation, and then re-open again at maturity to allow the seed to escape.
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.
Japanese Knotweed (Fallopia japonica) was introduced from Japan in the 1800’s as an ornamental; it was widely cultivated, escaped and is now well established throughout the Northeast. The World Conservation Union lists Japanese Knotweed among the top 100 worst invasive plants. Its dense canopy and rapid spread through underground rhizomes make it a formidable threat to native plants and the animals that depend on them.
There are some redeeming qualities to this invasive plant, however. In addition to goldenrod and asters, Japanese Knotweed is a crucial source of late-season nectar and pollen. At this time of year, when Japanese Knotweed flowers, you can almost locate a stand using just your ears, the buzzing of honey bees gathering the last of their winter food supply from the thousands of tiny flowers is so loud. A wide variety of insects can be found on this member of the Buckwheat family eating leaves, foraging for nectar and pollen, and preying on the former. A recent survey revealed honey bees, bumble bees, ladybug beetles, flies, hornets, yellow jackets, stink bugs and tussock caterpillars, to name just a few.
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The 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)
Having known since childhood that most insects have only one pair of antennae, imagine my surprise when I came upon a hornet on Queen Anne’s Lace that appeared to have two: a pair of slender, black antennae, and between them, a shorter pair of white ones. A bit of research revealed to me that in fact, these white “antennae” were actually the pollen sacs (pollinia) of an introduced and somewhat invasive orchid, Broad-leaved Helleborine (Epipactis helleborine).
Broad-leaved Helleborine is entirely dependent on insects to spread its pollen, especially wasps. It attracts them with nectar, which is said to have an alcoholic and narcotic effect which may help with the spreading of pollen, as an inebriated wasp is less likely to clean pollen off its body before leaving. Helleborine also produces a chemical which other plants produce and use to signal that they are being attacked by insects. It is used purely as a ruse by Helleborine, in order to attract wasps, Helleborine’s primary pollinators, who arrive to fend off other insects, and end up inadvertently collecting Helleborine’s pollinia.
Unlike the pollen of most plants, Helleborine’s pollen grains are so sticky that they cannot separate – thus, the entire package of pollen remains intact and is removed at one time. Wasps are capable of reaching the plant’s nectar without disturbing the pollinia, but cannot crawl out of the flower without striking against and detaching them and in so doing, getting them stuck to their heads. Can you find the pollinia in the insert photograph of a Broad-leaved Helleborine flower (which has not been visited by a wasp yet)?
Due to computer issues, Naturally Curious will resume posts next Tuesday, August 16.
Butterflies pollinate during the day while most flowers are open and they have better color perception than bees or even humans, but they are less efficient than bees at moving pollen between plants. Their legs and proboscis are longer and farther away from the flower’s pollen so they do not pick up as much pollen on their bodies. They also lack specialized structures for collecting pollen. Nevertheless, it is hard to imagine that some of the Daylily pollen that has collected on this Eastern Tiger Swallowtail’s wings might not fall onto or be brushed against the stigma of the next Daylily it visits.
With frost just a whisper away, and in some areas not even that, there are still hardy plants, many in the Composite family (goldenrods, asters, thistles, Queen Anne’s Lace, Yarrow), which defy the odds and optimistically send forth blossoms on the off chance that there are still pollinators on the wing. Fortunately for them, bumblebees can and do fly at much cooler temperatures than honeybees and other pollinators. When food is plentiful and outside temperatures fall below 50°F., bumblebees generally stay inside their nest and live off their stores. At times when food is scarce or stores are low, they will forage when the outside temperature is as low as 43°F. (In severe conditions they have even been known to vary their flying height to and from the nest to take advantage of any temperature differences.) Locally, Tri-colored Bumblebees (Bombus ternarius) have a near monopoly on the last vestiges of nectar and pollen (see photo).
Grass of Parnassus, Parnassia glauca, (also known as Bog- Star) was named after Mount Parnassus in central Greece. It is not a type of grass, but rather, belongs to the family Celastraceae and can be found growing in fens, bogs and swamps. The striking green lines on its petals guide flies, bees and other pollinating insects to the flower’s supply of nectar.
The structure of Grass of Parnassus’s flower is not typical. In between its five functioning stamens and five petals there is a whorl of five sterile stamens, each of which is three-pronged. The spherical tip of each prong mimics a glistening droplet of nectar. These stamens do not actually produce any nectar – they are there purely to attract pollinators. The actual nectar is located near the base of these false, or sterile, stamens. Only one of the five true stamens in the flower is active at any one time, with each producing pollen on average once every 24 hours.
Turtlehead, Chelone glabra, a member of the Plantain family (Plantaginaceae), can be found growing along stream banks and wetlands throughout eastern North America. Its long arching upper lip, or hood, overlaps the lower lip like a turtle’s beak, giving Turtlehead its common name. 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 bumblebees, 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, but 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 bumblebees that are able to both enter the flower and to reach the nectar. If you look on the sides of the flowers, occasionally you will find where impatient bumblebees have chewed through to the nectar, avoiding the struggles involved in entering the flower in the traditional manner.
Goldenrod is one of the most important flowering plants for honeybees because it is a prolific producer of nectar and pollen late in the year. Blooming in the late summer and fall, this bright yellow-flowered composite provides nectar for the bees to build up stores of honey for winter. (Goldenrod honey is dark amber and strong tasting.) Goldenrod also provides pollen to help stimulate the colony to produce brood late into the fall. The pollen adds considerable amounts of protein, fats, and minerals to the diet of the late-season bees, helping ensure that they will have food throughout the winter.
Ragged Robin, Lychnis flos-cuculi, is native to Europe and has become so abundant in northern United States that it borders on being considered an invasive plant. Found usually in wet areas such as marshes, fens and wet meadows, this perennial can cover an area as large as an acre. When flowering, Ragged Robin is very noticeable — not only to humans, but also to the many insects that pollinate it. Bees and butterflies, especially, flock to stands of this plant in order to obtain its nectar and white pollen. (If you suck the base of the flower, you will soon detect the sweetness that attracts pollinators.)
The flowers of Pitcher Plants are just as unusual and fascinating as their insect-luring leaves. These plants can be found blossoming during a two to three week period in the spring (late May-June). Although the maroon petals hanging down typically prevent you from seeing the structure of the flower, it more or less resembles an upside-down umbrella. Within one to two days of the flower opening, the stigmas become receptive and the anthers shed their pollen, which falls into the umbrella-like tray where insects travel on their way to the stigmas. Ants are almost invariably present in the flowers, attracted by the abundant nectar, but they are probably of little importance as pollinators. Bees and flies appear to be the primary pollinators of Pitcher Plants.
The blossoms of many shrubs are not necessarily big, flashy, strong-scented flowers, especially if they are wind-pollinated and have no need to attract insects. Beaked Hazelnut’s flowers are now blooming – pendant male catkins loaded with pollen and ¼ “- diameter female flowers. The female blossoms should be examined through a hand lens – they are exquisite little maroon flowers with magenta highlights and pistils that curl this way and that, in hopes of catching pollen grains. One advantage to flowering now, before leaves are out, is that the wind-dispersed pollen has fewer obstructions.
Thank you for all your guesses, a vast majority of which were right on the mark. Bloodroot, Sanguinaria canadensis, is one of the first spring ephemerals to bloom. On sunny days its petals are open wide, closing at night when the temperature drops and on cloudy, rainy days (when pollinating insects are less apt to visit). Only pollen is produced by Bloodroot – no nectar. Even so, insects, especially mining bees, visit and collect pollen, and in the process often pollinate the flower.
The methods which Bloodroot employs in order to become pollinated are impressive, to say the least. While cross-pollination is preferable, self-pollination is better than nothing. To limit self-pollination, the female stigma becomes receptive before the male anthers of the same flower produce pollen. Furthermore, during the first few days of the flower opening, the anthers bend downward toward the outside of the flower, away from the receptive stigma, where they are easily accessible to insects. If insect pollination doesn’t take place by the third day of flowering, however, the anthers bend inward, contacting the stigma and self-pollinating the flower.
Most bumblebees, unlike honeybees, die in the fall. Only the young, fertilized bumblebee queens overwinter. When they emerge early in the spring, each must start a new colony, with no help from worker bees. The queen builds a ball of moss, hair or grass, often in an abandoned rodent nest or small cavity. Within this ball the queen builds a wax honey pot, and provisions it with nectar from early-blooming flowers. Next, she collects pollen and forms it into a mound on the floor of her nest. She then lays eggs in the pile of pollen, and coats it with wax secreted from her body.
The queen bumblebee keeps her eggs warm by sitting on the pollen mound, and by shivering her muscles, raising her body temperature to between 98° F. and 102° F. For nourishment, she consumes honey from her wax pot, which is positioned within her reach. In four days, the eggs, all of which will become female workers, hatch. The bumblebee queen continues her maternal care, foraging for pollen and nectar to feed to her larvae until they pupate. After this first brood emerges as adult bumblebees the queen concentrates her efforts on laying eggs. Unfertilized female worker bees raise the larvae and the colony swells in number. At the end of summer, new queens (females) and males are produced in order to allow the colony to reproduce. After the new queens mate and become fertilized, the males all die, along with the female worker bees. The queen then seeks shelter for the winter. (Photo: Tri-colored Bumblebee queen collecting Trailing Arbutus nectar or pollen)
At a time of year when nectar and pollen sources are few and far between, New England Aster provides many species of bees with food. This composite seems designed specifically for easy pollination. Its open, wide flower shape provides a flat surface for insects to land on, and because the nectar and pollen are not hidden deep inside the flowers, both long- and short-tongue bee species can easily access them. Unlike honeybees, bumblebees do not have a large store of honey in their nests, so they need pollen and nectar throughout the season. Thus, the few flowers such as New England Aster that blossom as late as October are visited frequently and in large numbers. (Only the queen bumblebee overwinters, but the workers continue collecting nectar and pollen up until they die in late fall.)
New England Aster flowers close at night, when there are fewer pollinating insects flying. If an unusually cool period arrives during the time when New England Aster is blooming, the blossoms also close. Although it may seem that the aster is losing pollination opportunities during a cold day, bees are not very active in cool weather.
Blue Vervain (Verbena hastata) is a fairly tall (2 – 5 feet) flowering plant found in wet meadows. Its flower spikes branch upwards like the arms of a candelabra, and each has a ring of blue-purple flowers. The flowers at the bottom of the spike bloom first, and the ring of flowers advances upwards to the tips of the spike. Although Blue Vervain flowers have no scent, both long- and short-tongued bees are attracted to it primarily for its nectar, but also for its pollen. While Verbena Moth caterpillars feed on the foliage, most mammalian herbivores avoid eating this plant because of the bitter leaves. Various songbirds occasionally eat the seeds, including Cardinals, Swamp Sparrows, Field Sparrows, Song Sparrows, and Dark-eyed Juncos.
As with Pink and Yellow Lady’s Slippers, one of Showy Lady’s Slipper’s three petals is greatly modified into a large inflated pouch called the labellum. The two other petals attract pollinators with an alluring odor, but the insects that enter into this pouch are in for a disappointment, as lady’s slippers produce little or no nectar. Once inside, visiting insects are guided by very fine, slanting hairs on the inner surface of the pouch towards the flower’s pistil and stamens. Once it has entered the constricted passageway that leads to the reproductive parts, an insect cannot turn around and must pass by the pistil and stamens. Lady’s slippers rarely self-pollinate, so it is crucial that they not only attract, but also extract pollen from insects to achieve cross-pollination. Thanks to their structure, this happens more often than not. The flowering of Showy Lady’s Slippers peaks in Mid-June in central Vermont; if you know of a nearby fen (peat wetland that gets its water from rainfall and surface water), best visit it soon, as that’s where you’re most likely to find this species of orchid.
If you’ve noticed yellow clouds near pine trees recently, or a layer of yellow “dust” on your car or pond, you’ve witnessed the annual dispersal of pollen by male pine cones. Light and fluffy so as to be easily distributed by the wind (rather than insects), these minute pollen grains containing sperm cells can be found just about anywhere this time of year, including the nostrils of humans. All pines have separate male and female (seed) cones on the same tree. Male pine cones, which produce pollen, are much smaller, occur in clusters, are more papery, and remain on the tree for a much shorter period of time than most female pine cones. (By July they will litter the ground beneath pines before they quickly disintegrate.) Although it may mean a brief period of sneezing has to be endured by those allergic to it, this “golden smoke” not only creates beautifully intricate patterns for us to enjoy and makes it possible for pine trees to make the next generation of seeds, but it is also touted as an agent of increased testosterone and strong sexual libido, anti-aging, skin rejuvenation and improved immune systems for humans. Haste ye to a natural food store (or the closest pond!). (photo – Red Pine pollen & male cones)
A walk in deciduous woodlands at this time of year could result in the sighting of several species of orchids, one of which, Showy Orchis (Galearis spectabili), has a stalk of several flowers which typically bear lavender hoods (one variant is white). Potential pollinators, most of which are long-tongued bumblebees, butterflies, moths and bees, land on a white petal below the hood which acts as a “landing pad.” The insect next heads for the tip of the nectar-filled spur located at the back of the flower. In getting there it brushes against, and often picks up, packets of pollen (pollinia) before moving on to the next blossom, where cross-pollination ideally takes place. (Thanks to Ginny Barlow for photo op.)
Ninety percent of bees are solitary – the fertile females create their own cells and feed their own young, with no help from a colony of worker bees. They often nest underground, rarely sting and are excellent pollinators, even though they don’t store honey. Colletes inaequalis, a type of Plasterer Bee also known as the “Polyester Bee,” and “Unequal Cellophane Bee,” is a solitary bee. It derives its common names from the practice of lining its underground nest cells with a secretion that, when it dries, forms a smooth, cellophane/polyester-like lining. This cell holds one egg suspended above a collection of pollen and nectar on which the larva will feed. The Unequal Cellophane Bee is crepuscular, which can be deduced by the large size of its eyes. It is one of the earliest species to become active in the spring, sometime between March and May, when adults bees emerge from underground chambers off a vertical tunnel dug by their mother last spring. (Why it is called an “Unequal” Cellophane Bee I have not been able to determine.)
Like Bloodroot and many other spring ephemerals, Trout-Lily (also known as Dog-tooth Violet and Adder’s Tongue) remains closed at night and on overcast days. On sunny days, bees are its main pollinators, but it is visited by many other insects, including Red-necked False Blister Beetles that feed on both its pollen and ovules.
When a bee visits a Trout-Lily flower, it usually removes half of the available pollen in one visit. In no apparent hurry, it often pauses in the middle of collecting to groom itself and pack pollen into the pollen baskets on its hind legs. It then heads directly back to its hive to unload the pollen. Unfortunately for the Trout Lily, this hampers cross-pollination, as it severely limits the amount of pollen that reaches other Trout Lily flowers. As compensation, Trout Lily has two sets of anthers – one set opens one day, the other opens the next, preventing a bee from collecting all the pollen from a given flower in one day, giving other insects the opportunity to cross-pollinate. (Photo: Red-necked False Blister Beetle)
Jewelweed (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.
Bottle 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).