An online resource based on the award-winning nature guide

Self-pollination

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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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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Bloodroot Pollination

4-30-15  bloodroot 084Thank 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.

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Showy Lady’s Slippers Flowering

6-23-14 showy lady's slipper 139As 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.

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