In late September in these latitudes a lovely white and yellow aster or daisy with stiff white ray petals surrounding a yellow center is often found blooming along roadsides, empty lots and those areas plant people call “waste places”. I think of these waste places as remnant patches of “green” where nature survives—but sadly—only temporarily.
Though Daisy Fleabane begins flowering late in summer, its blooms persist well into fall. When most plants have long ago lost their flowers the Native American Daisy Fleabane (Erigeron annuus) persists to produce lovely eye catching masses of white and yellow flowers.
The plant may grow to a meter to 1.5 meters tall. Its leaves are alternate, long, narrow and smooth (lanceolate shape) and they have no stem or petiole (are sessile). The leaves clasp the main upright stem of the plant which is hairy. The flowers have pure white petals and a yellow center and are small, or about 2-3 cm in diameter. The flower bracts arise from the point at which the leaves arise (the axil). Flowering stems are more common on the upright parts of the plant, so that a mature plant may present a bushy appearance of many white and yellow flowers.
The “daisy” designation is a term used in the Middle Ages for this family of plants. Its naming may have been related to the fact that they displayed what appeared to be a yellow sun surrounded by white solar rays. Like the sun itself, the flower was envisioned as the “day’s eye”. That name was corrupted over time into “daisy”. The scientific name “Erigeron” may have its origin in the stiff white “solar rays” which surround the yellow center. They remind me of the stiff white beard of an old man. The Greek origin of the genus is derived from the root “eri” = early and “geron”= old man. Or the “early old man”, perhaps related to the fact that some specie of this genus appear early in the spring and that the ray flowers (at least to me) appear as noted above, stiff white whiskers of an oldster.
The Daisy Fleabane, is classed within the family of Asteracea, Compositae, or simply “daisy type flowers”. The appellation is valid it looks very much like a miniature standard daisy such as the English Daisy (Bellis perennis) or even a Montauk Daisy. But being a “fleabane” is questionable. There is no evidence to suggest it may act to help alleviate an infestation of fleas. The collection with flea-riddence may been a case of simple transfer of reputation. There is a British species, Blue Fleabane (Erigeron acris), which has a bitter taste, hairy texture and distinctive scent. These characteristics suggested to early British herbalists that the plant may have chemical properties that may repel the common flea. The crushed leaves of the dried Daisy Fleabane does emit a faint scent of camphor which may have encouraged homemakers in colonial times to dry the leaves and sew them into sachets for use in closets and clothes closets.
What is interesting about the entire clan of Asters or Compositae family of plants is their flowers. Daisy Fleabane’s attractive white and yellow “flower” is in fact a composite of hundreds of small flowers (or florets) all packed together in a flat receptacle to better attract the attention of pollinators such as bees, certain flies, moths and butterflies.
Compositae flowers have evolved two types of florets: the outer white ray flowers or “ray florets”, and the center yellow “disk florets”. In the Daisy Fleabane the disk florets are brightly colored (yellow) and are “perfect:, i.e. having both stamens and pistil (or male and female parts). The ray florets are pistilate (or have only the female part). It is the ray florets which produce a long prominent rays or petals which forms the outer ring of “petals” of the composite flower. There are twenty or thirty disk florets with stiff white petals in our local Fleabane flowers. These are often are sterile. The disk florets attract bees and butterflies and have special structures which help to facilitate fertilization. It is the disk florets which eventually produce the seeds. These can be seen clearly in a sun flower where the large sunflower seeds are produced within the disk position of the receptacle. While a sunflower may have hundreds of ray florets and as many appetizing striped or black seeds.
The interesting question of the Compositae is why and how did they evolve. It is apparent that being a composite flower offered a plant a survival advantage..but what was it?
Seed bearing plants —gymnosperms—bearing naked seeds protected in cones (related to modern spruces and pines) arose in the late-middle Paleozoic Era or the Carboniferous Period ( about 300 million years ago)k. These plants produced clouds of pollen which was dispersed into the air to pollinate near by plants. The seeds of gymnosperms like pine and spruce often had seed parts which helped to disperse the seeds by wind.
Almost 200 million years later, in the Cretaceous Period of the Mesozoic Era plants with specialized organs called “flowers”arose. These flowering plants, or angiosperms, had a seed-ovum enclosed by an egg bearing organ called an ovary or pistil. When pollinated the ovum matured into a hard coated seed and the pistil grew into fleshy fruit (or related organ). The fruit was often attractive as a food source to other organisms. These would consume the fruit and carry away the coated seed in its digestive system. The advantage was better, more efficient pollination and seed dispersal. Early flowering plants also used wind pollination to fertilize the flower. These flowers had to produce enormous quantities of pollen to insure pollination.
But this story involves both plants and animals co-evolving into a complimentary relationship. Bees are insects which had evolved to feed on the pollen of flowers. They evolved about 120 million years ago in Early Cretaceous from a form of predatory wasps.
During the Early Cretaceous Period with the rise of flowering plants some of these wasps began exploiting flowers and began specializing in collecting pollen (and later nectar) from flowers to sustain themselves and their hives.
In the Late Cretaceous (about 80 million years ago) as a result of competition among the flowing plants to attract bees, flies, moths, and butterflies to pollinate flowers, a new family of flowing plants evolved —the Compositae or “daisy family”. But once bee pollination became established sometime in Mid Cretaceous flowing plants faced completion on how to effectively attract pollinating insects…to produce more seeds..and to complete targeted pollination. Thus the composite structure evolved which concentrated large numbers of small flowers in a format that would attract pollinators most successfully. They also evolved the pappus or fine threads which adhere to their tiny seeds. The pappus threads permit the tiny seeds of the Daisy to take advantage of wind to disperse seeds more effectively
Evidence of the rise of the Compositae consist of pollen recovered in Antarctica dated to 80 million years ago or Late Cretaceous. Thus, over a period of about 40 million years ago (120-80 mya) a new form of plant evolved to better attract insects such as bees and butterflies.
These plants instead of simply multiplying the number of flowers they produced on a plant…multiplied the reproductive part of the plant in large receptacle which would attract pollinators effectively by colder and shape and facilitate effective pollination
From the Cretaceous (80 million years ago) onward flowering plants and bees (as well as other insects) co-evolved with each other to specialize in pollination for plants and exploiting pollen and nectar for the bees and other insects.
Pollination by bees was more efficient. Wind pollinated flowers had to produce enormous quantities of pollen as great cost of energy to the plant. .Much of the pollen was wasted. While pollination by bees was more efficient, more effective and gave bee-pollinated plants and gave the Aster-like of Daisy family (Asteracea or Compositae) advantages in areas where wind was not effective, or over large distances where wind pollen was no likely to occur.
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