There was plenty of ignorance in medieval times, but in case you were wondering, farmers and gardeners *did* know the value of manure. In fact, it’s good to view the period as a time in which nearly every kind of material or thing was scarce and had value: rags, candle ends, meat scraps and broken glass all had market value. Fecal waste from animals and humans was no exception.
Rights to animal dung were guarded as closely as the rights to anything else. Fields lying fallow could have animals grazing there, enriching the soil during its time off. Barn waste was used or sold. People in town sometimes kept chickens or doves, and this waste was used in their herb gardens or sold. Houses in town typically had latrine sheds out back, along the alley, often shared by several families. Every few years, these had to be dug out, and the digger sold the contents at a profit. Aged and dried, it was as good as any manure.
In contrast to farm fields, gardens used separate, often raised, beds with sand or gravel paths between the growing areas. Some gardens were near enough to streams that the gardener could maintain channels and furrows with miniature dam walls so that the beds could be irrigated. Other gardeners had to use an earthenware pot with holes in the bottom. They walked along the rows, swinging the pot, and then plugged the filling hole with a thumb, tipping it upside-down, to stop watering.
As today, gardeners then fought with nuisance insects. They dumped sawdust on nearby anthills, killed caterpillars with ashes, and edged the garden with herbs thought to repel other insects.
Grafting fruit trees and pruning vines were skilled crafts. Toward the end of the Middle Ages, large cities had full-time nurserymen who sold seedlings and saplings. They were already working to develop better hybrids, especially with fruit trees and grapes.
Garden tools were simple forms of the ones we know today: hoes, rakes, spades. Most of each tool was made of wood, with only edges covered with iron. The price of iron came down all through the medieval period, but at no time was it plentiful enough to waste on simple tasks like digging and weeding.