This section is from the book "British Wild Flowers - In Their Natural Haunts Vol2-4", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
Though the more native Knapweed is only known from its present-day distribution in Europe, West Siberia, N.W. India, being an introduction in X. America, the Corn-flower is found in Neolithic beds at Edinburgh with other weeds of cultivation and flax. In Great Britain it is absent from Monmouth, Brecon, Radnor, Carmarthen,
Montgomery, Merioneth, Pembroke, N. Lines, Cumberland, Isle of Man, Dumfries, Wigtown, Selkirk, Stirling, Mid and N. Perth, Can-tire, S. Ebudes, N. Ebudes, Orkneys, but elsewhere it is general from Moray to the English Channel, and in the Highlands grows at a height of 1000 ft. By Watson it was considered a colonist.
Bluebottle is a cornfield plant, always coming up spontaneously in cultivated fields, or on waste ground, or in gardens, being associated with such plants as Stork's Bill, Common Melilot, Chicory, Viper's Bugloss, Yellow Toadflax, and other casuals.
Apart from its lovely flowers, Bluebottle has a characteristic habit. It is an erect plant, with the stem repeatedly dividing, and thus inversely triangular in outline. The stems are slightly angular, and densely cottony and hollow. The stem-leaves are alternate, stalkless, linear, with several nerves, acute, the radical leaves broader, and more blunt, often deeply divided, covered like the stem with a web of cotton.
The flowers are of a deep blue, on simple flower-stalks with dark threadlike anthers. The whorl of leaflike organs has notched leaves fringed with hairs, narrowly elliptical, and overlapping semi-transparent margins which run back. The hair is shorter than the fruit. There are scales in the receptacle.
The stem is 1 - 3 ft. high. The Corn-flower is in flower in June and up till August or September. It may be annual or biennial and reproduced by seed. It is worth cultivating, and is indeed a garden plant.
The plant is downy, but the involucres forming the flowerhead are bordered with turned-back teeth, which serve as a chevaux de frise to exclude ants. There are no prickles on the stem and leaves. The ray florets are neuter. The anther-stalks of the stamens are able to contract, so that the anther-cylinder is drawn down 2-3 mm. and slowly up to 4 - 6 mm., returning to their original position in ten minutes. They lose the power of contraction when the stigmas are ripe. The ray florets are large and funnel-shaped, and radiate outwards, attracting insects, and make the width of the flower head 20 - 50 mm. On the opening of the flower the pollen lies between the pistil and the hood which the anther-heads form. The stamens are sensitive and contract when touched, so that they expose the pollen. The hairs are the sensitive portions. The stigmas later open and curl over, and the flower is bound to be pollinated.
Honey can easily be reached, for the flower is wider for 3 mm. above the narrow tubular part, up to the point where it is divided into narrow linear segments, and pollination is largely simultaneous.