The Forest Unseen: A Year's Watch in Nature by DavidGeorge Haskell Page A
Authors: DavidGeorge Haskell
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task, either to shed pollen or to harvest pollen from the wind.
Although the mandala’s plants share a hermaphroditic design, their geometry differs markedly from species to species. The
Hepatica
’s anthers grow in a thick bush around a cluster of pillarlike styles. Blue cohosh’s pallid ivory flowers have globular anthers squatting around a bulbous ovary with minute stigmas. Toothwort’s petals enclose a sheath around the hidden anthers. Only spring beauty has a flower somewhat like the chickweed. Its three stigmas sit atop a drooping trident, circled by five pink-tipped anthers.
This variety reflects the tastes of the plants’ pollinators but is also caused by less obvious forces. Nectar robbers, for example, exert a stealthy but powerful influence over floral design. An ant has buried its head in a spring beauty flower in front of me. I use the hand lens towatch it bypass the pollen and stigma, then upend and steal the flower’s sugary nectar. This robbery is the cost borne by open-cupped flowers for welcoming a diverse set of pollinators: freeloaders move in and exploit your openness. Spring beauty flowers choose the most welcoming, and therefore the most vulnerable, strategy by freely offering nectar inside an open cup that is accessible to any insect.
Hepatica
and rue anemone also produce open cups, but neither offers nectar. These nectarless flowers lose little energy to thieves, but they are also less attractive to bees. Toothwort offers nectar enclosed in a tube that excludes robbing ants but restricts the number of bees that can reach into its recesses for nectar.
The diversity of floral design is also affected by the longevity of plants and their flowers. Blooms that last for just a few days, such as those of spring beauty, are desperate for pollinators. This favors a bohemian style, risking all for the kiss of a bee. If the bee’s embrace is accompanied by some ne’er-do-wells, so be it. Longer-lived flowers can be more restrained, holding back the nectar or enclosing their bloom in the knowledge that sooner or later a decent suitor will come along. The longevity of the plant that produces the bloom also factors into the economy of flowering. All the spring ephemerals are perennials that sprout from underground roots or stems. If a creeping stem lives for three decades, it can afford to be restrained in its search for pollinators. A shorter-lived root might be more willing to tolerate a few freeloaders. Both factors, the duration of the bloom and the longevity of the plant, are variants of the same theme: shorter lives must burn brighter.
Flowers therefore perform economic gymnastics as they balance losses to robbers with the need to lure pollinators. How this performance unfolds depends not just on the insects flying around the mandala but also on the ancestry of the plants. Natural selection tinkers with the raw materials provided by previous generations, so each flower’s design is shaped by the particularities of its genealogy. Different plant families have different sets of equipment, constraining their acrobatics.
Hepatica
and rue anemone belong to the same family, the buttercups, all of which produce nectarless flowers with open cups. Great chickweed belongs to the pink family. This family’s name comes from the common name of
Dianthus
, a sweet-smelling garden flower. The flower named the color pink, and the jagged edges of its petals also gave their name to pinking shears, scissors that dressmakers use to cut zigzag edges. The “pink” plant family is named for the shears, not for the color—great chickweed inherits a tendency for serrated petals. At first glance, its ten slender white petals seem to have broken away from familial tradition. A closer look shows that the flower has just five petals, each one so deeply cleft that it seems to be double. Chickweed therefore pushed to the limit its family’s preference for ornamented displays and created an illusion of extra petals.
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Although the mandala’s plants share a hermaphroditic design, their geometry differs markedly from species to species. The
Hepatica
’s anthers grow in a thick bush around a cluster of pillarlike styles. Blue cohosh’s pallid ivory flowers have globular anthers squatting around a bulbous ovary with minute stigmas. Toothwort’s petals enclose a sheath around the hidden anthers. Only spring beauty has a flower somewhat like the chickweed. Its three stigmas sit atop a drooping trident, circled by five pink-tipped anthers.
This variety reflects the tastes of the plants’ pollinators but is also caused by less obvious forces. Nectar robbers, for example, exert a stealthy but powerful influence over floral design. An ant has buried its head in a spring beauty flower in front of me. I use the hand lens towatch it bypass the pollen and stigma, then upend and steal the flower’s sugary nectar. This robbery is the cost borne by open-cupped flowers for welcoming a diverse set of pollinators: freeloaders move in and exploit your openness. Spring beauty flowers choose the most welcoming, and therefore the most vulnerable, strategy by freely offering nectar inside an open cup that is accessible to any insect.
Hepatica
and rue anemone also produce open cups, but neither offers nectar. These nectarless flowers lose little energy to thieves, but they are also less attractive to bees. Toothwort offers nectar enclosed in a tube that excludes robbing ants but restricts the number of bees that can reach into its recesses for nectar.
The diversity of floral design is also affected by the longevity of plants and their flowers. Blooms that last for just a few days, such as those of spring beauty, are desperate for pollinators. This favors a bohemian style, risking all for the kiss of a bee. If the bee’s embrace is accompanied by some ne’er-do-wells, so be it. Longer-lived flowers can be more restrained, holding back the nectar or enclosing their bloom in the knowledge that sooner or later a decent suitor will come along. The longevity of the plant that produces the bloom also factors into the economy of flowering. All the spring ephemerals are perennials that sprout from underground roots or stems. If a creeping stem lives for three decades, it can afford to be restrained in its search for pollinators. A shorter-lived root might be more willing to tolerate a few freeloaders. Both factors, the duration of the bloom and the longevity of the plant, are variants of the same theme: shorter lives must burn brighter.
Flowers therefore perform economic gymnastics as they balance losses to robbers with the need to lure pollinators. How this performance unfolds depends not just on the insects flying around the mandala but also on the ancestry of the plants. Natural selection tinkers with the raw materials provided by previous generations, so each flower’s design is shaped by the particularities of its genealogy. Different plant families have different sets of equipment, constraining their acrobatics.
Hepatica
and rue anemone belong to the same family, the buttercups, all of which produce nectarless flowers with open cups. Great chickweed belongs to the pink family. This family’s name comes from the common name of
Dianthus
, a sweet-smelling garden flower. The flower named the color pink, and the jagged edges of its petals also gave their name to pinking shears, scissors that dressmakers use to cut zigzag edges. The “pink” plant family is named for the shears, not for the color—great chickweed inherits a tendency for serrated petals. At first glance, its ten slender white petals seem to have broken away from familial tradition. A closer look shows that the flower has just five petals, each one so deeply cleft that it seems to be double. Chickweed therefore pushed to the limit its family’s preference for ornamented displays and created an illusion of extra petals.
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