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.
Larkspur is unknown in a fossil state. It belongs to the Warm Temperate Zone, growing in Central and S. Europe, North Africa, and has been introduced into the United States of America. It was regarded by H. C. Watson as an alien or colonist, and as naturalized in Cambridgeshire, but elsewhere sporadic.
The Larkspur is a plant of the Eastern counties, which has become established where arable land still remains. Doubtless, since it is an old garden favourite in another form, it was once much commoner than it is to-day. Now it is only with good fortune that one may expect to find it in East Anglia in the cornfields, where it gives just that blue tinge to the growing grain that is to be seen more extensively where the Cornflower grows.
Chalky or calcareous soil suits it best.
Larkspur is a tall, erect plant, with many spreading branches, and the numerous flowers in the raceme or flowerhead give it a handsome appearance, and this is noticeable in the cultivated form in our gardens. The leaves are much divided, with linear lobes.
Its first Latin name was bestowed on it in reference to the shape of the nectary, like the mythical dolphin. The second name was given in allusion to the fancied resemblance between some markings, like Aia, upon the flower. The terminal crowded racemes or flower-heads have as many as sixteen flowers, white, purple, blue, etc. The seeds, which are numerous, black, and angular, have transverse undulating ridges around them. The style is awl-shaped. The follicles or fruits are downy or smooth.
The plant is 1 to 2 ft. high, flowering in June and July, and is annual.
In this, as in D. consolida, 2 petals have united. The posterior sepals form a spur. The 2 upper petals have united by their back-wardly-directed processes into a single spur in the point of which honey is secreted. The enlarged parts of the upper petals turned forward lengthwise are united into an inner spur, and when the bee enters cannot be thrust on one side. They form a sheath with the lower petals, only open below. At first the anthers, in the second case the stigmas, touch the bee below the head. The lower petals unite with the upper.
And yield at the side when the bee, which must have a long proboscis, attempts to thrust in its head. Cross-pollination is caused by insects, and self-pollination will take place in any case. Larkspur is generally pollinated by humble-bees. The seed of the Larkspur is dispersed by the wind. The seeds are black and angular and ridged, and contained in a follicle or dry fruit, and are shaken out only by a strong wind.
The Larkspur is a lime-loving plant and requires a lime soil, being suited to districts where chalk or limestone contributes to form a subsoil of a limy character.
This plant is not infested by micro-fungi.
The moths Chariclea Delphinii and the Viper's Bugloss moth (Dianthoecia Echii) visit it, as also Heliothis dipsacea.
Dioscorides gave the name Delphinium (Greek delphis, a dolphin) from the form of the nectary. Ajacis is from Ajax (Greek, Aias), from markings like Aia. Larkspur is the only name, perhaps in allusion to the length of spur like the toe of the lark's foot.
The plant is a favourite in our gardens, and the flowers have been varied considerably by cultivation.
Essential Specific Characters: 14. Delphinium Ajacis, Reichb. - Stem erect, leaves alternate, multifid, flowers in raceme, sepals united, petals small, spurred, blue, white, pink, follicles 1 to 5, downy, seeds wrinkled.
Photo. J. H. Crabtree - Larkspur (Delphinium Ajacis, Reichb.