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.
As the storehouse of the crops, a stackyard is a centre of dispersal for the majority of agrestal plants, which grow up with the corn, and are cut with it, the seeds falling out during cartage, or in the winnowing or threshing being blown out in the process. The area around a stack is open, being kept clear of weeds, so that there is every possibility of the successful germination and growth of such plants.
The farmyard forms a similar dumping ground for a number of pasture and arable soil plants that grow luxuriantly in the open ground, or near manure-heaps. The origin of such weeds differs from that of those of the stackyard to some extent (or rather the indirect dispersal). Primarily they come from the meadow (as hay), or from the cornfield (as straw). Hay is used as fodder for live-stock, and in this way seeds in the refuse, or in the carriage of hay from the stack to the stable or cowshed, get dispersed. The same applies to straw. But the refuse hay and the straw used for bedding are utilized as a sort of binding for manure, and in this and the latter, when turned out in the farmyard, seeds retaining vitality occur, and germinate on the moist and warm manure-heap. Apart from this, the wind-scattered seeds previously mentioned tend to grow luxuriantly in the refuse manure scattered here and there.
The following plants are characteristic: Shepherd's Purse, Common and Round-leaved Mallow, Melilot, Black Mustard, White Mustard, Burdock, Spear Thistle, Chicory, Hawksbeard, Dairy Maid's Dock. Others are Scarlet Pimpernel, Veronica Tournefortii, Corn Sow Thistle, Poppies, Charlock, etc.
The relationship of gateways to the highways, and their characteristic florula, havealready been mentioned (under Section VI); but gateways are not confined to highways, though they are naturally more frequent there than elsewhere, comparatively speaking.
The plants that occupy such ground owe their position on both sides of the gateway to their dispersal by much the same method as plants along the cart-road. The foddering of live stock around a gateway is again a constant source of distribution of plants characteristic of this type of artificial habitat.
The following plants are generally to be found in proximity to gateways, viz.: Knotgrass, Great Plantain, Charlock, Wart Cress, Dairy Maid's Dock, Scentless Mayweed, Burdock, Groundsel, etc.
The quarry is an artificial exposure of rock, or loosely compacted or clayey beds, which is opened up for economic purposes. Compared with natural exposures of rocks in cliffs, or upon hills, or other places where there is a natural outcrop, the flora is on the one hand similar, or on the other dissimilar.
The similarity is due to the colonization of such exposures by plants native to the particular type of rock or soil. The form of the exposure determines the type of plants that will more or less naturally find a foothold there. In some cases crevice plants, or those that grow upon bare patches of rock, quickly appear, and flourish as luxuriantly as in natural exposures. The presence of springs or the dripping character of the rock will determine the presence of others. The dissimilarity between the flora of a quarry and that of a natural exposure of rock, etc., is due to the presence of numerous weeds or plants, alien to the locality or rock soil, which occur in varying proportions in the former type of habitat.
The mode of introduction of such plants is not easy to determine, for this may be diverse. It is highly probable, however, that the wind plays a considerable part in this respect. Rock-faces act as barriers to the further dispersal of wind-sown plants, as to the dissemination of the fruits and seeds. Probably the plants more or less native to the district are dispersed by this means. But in a quarry there are frequently a number of other plants, obviously brought from a distance - in some cases foreigners or true aliens - that are undoubtedly brought by other agencies.
Chief amongst these is the horse traffic in quarries, and the dispersal of fodder plants for this reason. Birds may disperse some plants with indehiscent fruits, as quarries are favourite resorts of birds. Foxes and other mammals, e.g. rabbits, may do the same by carrying the seeds or fruit in the mud on their feet, in these last two cases from no great distance.
Deadly Nightshade is sometimes found in quarries. Other plants are Dyer's Weed, Rose-bay, Anthyllis, Barbarea praecox, Melilot, Flax, Senecio viscosus, Hare's Foot Trefoil, Trifolium incamatum, T. ochro/eucon, Lucerne, etc.