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.
Taking first the areas immediately around the habitations of man, who is the chief agent in the introduction and dispersal of alien plants, there are the hedgerows and other kindred spots in close proximity to villages or towns, or the boundaries of cultivated tracts, where certain plants are usually to be found in a large number of similar spots, which occur around almost every village or town.
The Greater Celandine is one of these plants. Go where one will, it is nearly always possible to discover somewhere on the immediate outskirts of a village, in the hedge of a garden, or at the base of a loosely-made wall, a number of individuals of this plant. It is common on sloping banks where other plants do not grow, and where the soil is bare of vegetation. Its acrid juices may make the soil unfitted for other plants around it. Gout-weed and Tansy are further examples.
Borage, Comfrey, and Bittersweet occur in more open spots away from hedges, close to villages and gardens. These plants undoubtedly owe their dispersal to artificial causes, being used as remedies for various complaints from the Middle Ages down to the present time.
Walls, which will be described in greater detail in Section XII, are in themselves artificial, and support a number of characteristic mural plants that grow in the crevices or on the top, depending upon the rupestral type of habitat. At the base of walls, whether in villages or elsewhere, a certain type of habitat develops, which supports a typical florula akin to that of waste ground. The soil at the base is usually open. Water drips from the wall-top, forming hollows and loosening the soil. This is inimical to some plants, exposing their rootlets. Fragments of the brick or stone break off, or sand-blasts caused by sand from the macadam may undercut the materials.
Weeds are removed, especially grass, and quickly-growing annuals and some ubiquitous perennials take their place. The roadscraper disturbs the ground periodically. Shepherd's Purse is one of the most common types, growing at the base of the wall on open ground, and in a variety of similar spots, as on soil denuded for stone heaps, farmyards, etc. Common Mouse-ear Chickweed (also a plant of dry pastures) likewise frequents this habitat.
Common Chickweed is another familiar weed along the roadside at the bottom of walls. Cut-leaved Dead Nettle often grows at the base of a wall where there is a good thick deposit of road grit. The Hedge Mustard is another plant that is especially fond of this habitat. The Great Plantain, Veronica agrestis, Wall Speedwell (also mural), and Barley Grass may also be found in such situations. The last is especially characteristic.
Certain areas with a loose sandy soil occur here and there which may be described as waste ground, in the sense that they are not open to cultivation and are left in a more or less derelict condition. The plants that grow in such places are usually characteristic of dry sand soil. They include such plants as Stork's Bill, Musk Thistle, mentioned here, and others such as Lotus tenuis, Fuller's Teasel, Evening Prim-rose, Hare's Foot Trefoil, Bird's Foot Trefoil, Vernal Whitlow Grass, Cornflower, Mallow, and many other plants of doubtful origin, such as Treacle Mustard, Lepidium Draba, Sisymbrium pannonicum, etc.
This type of mixed association is similar to the vegetation that may establish itself upon a fixed dune after the fixation of the sand by Marram has been completed. When this is the case a large number of inland plants commence to appear, and the ordinary maritime vegetation of the sand dunes, which is not very extensive (in species), tends to disappear.
The effuse or much-branched Oraches,
A triplex patula and A. hastata, find a suitable habitat in the loose sand; and other common types are: Festuca rubra, Ononis repens, Lotus corniculatus, Erodium cicutarium, Cau-calis arvensis (now rare inland), Rumex crispus, Senecio Jacobaea, Taraxacum erythro-spermum, Hypochaeris radicata, Sambucus nigra, Trifolium repens, T. pratense, T. arvense, Rubus rusticanus, Potentilla reptans, P. anserina, Sedum acre (mural), Galium verum, Crepis virens, Hieracium Pilosella, Leontodon autumnale, Carlina, Cnicus arvensis, Myosotis collina, Thymus Serpyllum, Holcus mollis, Cynoglossum officinale, Anthyllis vul-neraria, Oenothera biennis, the last common upon the Lancashire coast. The origin of these plants is diverse, many coming from pasture or arable close to the sea.