An online resource based on the award-winning nature guide

Pollination

Hobblebush Flowering

5-5-17 hobblebush 065At this time of year moist, rich woods are brilliantly lit up with the white flowers of a scraggly shrub called Hobblebush, whose name is derived from the tendency of its sprawling branches to trip people walking through the woods.

Hobblebush’s inflorescences consist of clusters of blossoms that together can measure six to eight inches across. The smaller flowers in the center (still buds in this photo) are fertile, possessing both stamens and pistils, while the larger flowers in the outermost ring are sterile. The inner fertile flowers produce fruit if pollinated and fertilized. The larger outer flowers, being sterile, do not produce fruit — their sole function is to attract insects to pollinate the central mass of fertile flowers.

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Blue Cohosh Flowering

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Blue Cohosh, one of our early spring wildflowers, has diminutive flowers that open before its leaves fully expand. Like Wild Ginger, Blue Cohosh flowers are the color of rotting meat, which may account for the fact that flies are its main insect visitors. Flies tend to feed at a single flower until satiated, which is not conducive to cross-pollination, and thus most fertilization in Blue Cohosh is the result of self-pollination.

Native Americans treated a wide range of afflictions with Blue Cohosh, including gallstones, fevers, toothaches and rheumatism. The most common use of its rhizomes, or underground stems, was as an aid to speed and ease childbirth. Even today it still serves this purpose — 64% of midwives surveyed reported using Blue Cohosh to treat women before or during childbirth. It has, however, had deleterious effects on some women and has not been evaluated by the FDA.

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Carpenter Bees Hibernating

email-carpenter bee holes IMG_1408If your home, shed or barn has weathered, unpainted wood and is riddled with ½”-diameter, perfectly round holes, there is a chance that carpenter bees are hibernating in them. Carpenter bees resemble bumblebees in both size and appearance (a carpenter bee has very few hairs on the top of its abdomen, which appears black and shiny, whereas bumble bee abdomens are often yellow and hairy), but they are not social insects. Instead of having a common nest in which they live and raise their young, carpenter bees drill  holes in wooden structures or trees inside of which they chew tunnels that contain six to eight brood chambers for their young. After creating the chambers, the female carpenter bee places a portion of “bee bread” (a mixture of pollen and regurgitated nectar) in each one. On top of each pile of food she lays an egg and then seals off the chamber. The larvae eat and grow, pupate and emerge as adult bees in late summer. At this point they feed on nectar, pollinating a wide variety of flowers before they return to their tunnels to over-winter.

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Broad-leaved Helleborine Dispersing Pollen

8-10-16  helleborine pollinia 021Having 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.

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Butterflies As Pollinators

7-29-16  swallowtail in lily 086Butterflies 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.

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Large-flowered Trillium Flowering

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Large-flowered Trillium (Trillium grandiflorum), also known as White Wake-Robin, is our largest and showiest species of trillium.  It can be found throughout New England’s rich woods, sometimes carpeting large expanses of the forest floor in May and June.  All species of trillium, as their name implies, have parts arranged in threes, or in multiples of three (petals, bracts, leaves, stamens, carpels).

Nectar, not fragrance, attracts long-tongued bumblebees to Large-flowered Trillium’s funnel-shaped blossoms.  Self-pollination occasionally occurs, aided by the fact that as the flowers age, their stigmas reflex downward and come in contact with the anthers.  The flowers are exceptionally long-lived, remaining open and fertile for two to three weeks.

When they first open, Large-flowered Trillium’s petals are white.  As the flowers age, they become pale to deep pink (see insert).  (There is also a pink form of Large-flowered Trillium which is pink from the time of opening.) The seeds that form are dispersed primarily by ants, but yellow jackets, harvestmen and white-tailed deer also contribute to their dispersal.  It takes two years for the seeds to germinate and once established, Large-flowered Trillium plants typically require seven to ten years in optimal conditions to reach flowering size.

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Miterwort Flowering

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Miterwort (Mitella diphylla), also called Bishop’s Cap, is named for the resemblance of its two-peaked fruits to the hats (known as miters) worn by bishops of the Roman Catholic Church.  This spring wildflower produces miniature five-pointed snowflake flowers that beg to be examined with a hand lens.

Gnats, small bees and syrphid flies all seek out Miterwort for its nectar. Because its nectaries are located just below the stamens, the flower is pollinated by the mouthparts of the pollinators which brush against the stamens when collecting nectar and the inadvertently-gathered pollen is transported to other Miterworts.  Predators such as the Goldenrod Crab Spider (pictured) know that potential meals are plentiful near these delicate flowers.

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