This section is from the book "British Wild Flowers - In Their Natural Haunts Vol5-6", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
Long cultivated as it has been no seeds of the Wallflower have been discovered in early beds. It is confined to the North Temperate Zone in Central and North Europe. Everywhere it is only naturalized, being an alien plant which has become established solely on account of being a garden plant, easily propagated by seed, the amount of which, as in most Cruciferae, is enormous.
Like the yellow-flowered Wall Fumitory, the Wallflower, too, is a rock plant. Its occurrence on old ruins may sometimes mark the only remnants of a former domestic use of such buildings. Castle walls and enclosures are a frequent stronghold of the so-called Wild Wallflower. With it one may find the Martagon Lily and the Star-of-Bethlehem, these last being fond of humus but not rock habitats.
The plant is shrubby, having a smooth, stout main stem, or with a few hairs, with numerous ascending branches forked from the base. The leaves, which are entire, lance-shaped, and having appressed forked hairs, which are numerous, help to give it this shrub-like character. The hairs protect the plant from loss of moisture or from the sun.
The flowers are large, in racemes, the sepals erect, 1 in. across, fragrant, and in cultivation many-coloured. The stigma is bilobed with bent-back lobes, the pods are long and not transversely divided, but square. The pod opens by 2 valves all the way, and is divided by narrow compartments. The seeds are oblong, have a membranous oval border, and are in a single row in each cell. The valve of each pod has a rib in the centre. The embryo fills the seed, and the cotyledons are egg-shaped, flat, and pressed face to face.
The Wallflower reaches a height of 1 - 1 1/2 ft. It is in flower from April to June or July. It is an evergreen undershrub, perennial, and propagated by seed.
The flowers are large and conspicuous, sweet-scented and attractive to insects, and the stigma is provided with spreading lobes to assist insects to alight upon it and cause cross-pollination. There are 2 honey-glands at the base of the 2 stamens.
The seeds are dispersed by the wind or the plant's own mechanism. The seeds are flattened, and this assists in their dispersal by the wind when the pod has opened or dehisced lengthwise.
It is infested by a fungus, Peronospora parasitica. The beetle Bari-dius laticollis, and the Lepidoptera Large Yellow Underwing (Triphoena pronuba), Angle Shades (Phlogophora meticulosa), Plutella cruciferarum, P. porrectella, visit it.
The name Cheiri, or Keir in Arabic, was adopted by Linnaeus, who added anthos, Greek for flower. Cheiros means a man's hand, and it was called hand-flower. Gerarde (1597) called it Well Gilloflower.
The English names are Banwort, Bee Flower, Bleeding Heart, Blood Wall, Bloody Warrior, Chevisaunce, Churl, Geraflour, Gilli-flower, Heartsease, Jacks, Jeroffleris, Jilliver, July Flower, Keyry, Sweet William. It was called Winter Flower and July Flower because it flowers in winter and is more or less dead in summer. In Palestine it was called "Blood-drops of Christ". A legend is told of a maiden held captive on the Tweed banks, having plighted her troth with a member of a hostile clan. The rival chiefs fought and shed blood between each other. The lover at last gained admission as a troubadour and planned escape, he agreeing to wait for her:
Photo. J. H. Crabtree - Wallflower (Cheiranthus Cheiri, L.)
"Up she got upon a wall, Attempted down to slide withal; She fell, and bruised, she died. Love in pity to the deed, And her loving luckless speed, Turned her to this plant we call Now the Flower of the Wall."
The Wallflower is much cultivated, and many varieties of colour -yellow, white, orange, blue, purple flowers - are produced, both double and single. It has been grown in pastures with parsley, thyme, etc., for its acrid properties as a remedy for sheep rot.
Essential Specific Characters: 23. Cheiranthus Cheiri, L. - Stem shrubby, leaves linear-lanceolate, acute, with appressed hairs, flower yellow or red, calyx spreading, pod tetragonal, stigma 2-lobed.