A great many plants were used as sources for coloring matter in the Middle Ages, whether to furnish dyes or pigments.  Medieval plants such as madder, weld, woad, lady’s bed straw. Dyer’s broom, iris, calendula, celandine and saffron are being grown today in Manhattan and are part of the gardens of the Cloisters Museum.  The Bonefort Herb Garden at the Cloisters provides a rare opportunity to see more than 250 species of plants known and used in medieval Europe.  Two of these plant beds are devoted exclusively to dye plants and plants used in artist materials.  Depending on the garden of the medieval illuminator, a wide selection of coloring sources was available, especially when yellow was sought.  Yellow is the most common color yielded from plants.  According to Daniel Thompson, “Incomparably the most important yellow in medieval painting is the metal gold.  Yellow pigments, however, played a significant part in the pageant of medieval technique.  One of the most important services required of [the illuminator] was to imitate the appearance of gold.”

Weld, Reseda luteola, is one source of color used this way.  It is thought to be the most ancient yellow dye stuff known to man, and was cultivated throughout the Middle Ages.  It is a biennial, and produces a rosette of narrow dark green leaves in the first year of its growth and a flowering stem in its second.  After producing long slender flowers, the plat dies.  Fortunately, it produces a lot of seeds which will grow by themselves.  Once you have planted weld, you won’t have to plant again.  Weld has a long tap-root which is difficult to transplant; you should sow the seed on site where you want the plant to grow.  A decoction of weld can be readily made by chopping the leaves and flowers and steeping them in water.  This decoction, after being strained, can be mixed with alum and then precipitated onto a natural chalk base to form a weld lake.  This lake was chiefly used by manuscript painters, providing a bright vegetable yellow which could substitute for the poisonous mineral orpiment, a sulfide of arsenic, used to imitate gold.  Weld is available today from many herb suppliers who stock dye plants.

In addition to weld, two other plants now grown in the Cloisters garden were used as gold substitutes in the Middle Ages: saffron from Crocus sativus and greater celandine, Chelidonium maius.  (This should not be confused with the lesser Celandine, an unrelated member of the buttercup family).  Both celandine and saffron were used with powdered tin to achieve the effect of imitating gold.  Of the two, saffron was the more important, more permanent, and yielded a gold substitute more readily than celandine. 

Saffron, a member of the Iris family native to asia minor, is a crocus which blooms not in spring but in September\October.  Its narrow grassy leaves continue to grow throughout the winter period.  Saffron was much prized for both its color and its fragrance and has been cultivated from very ancient times, as it is today.  It is no longer found in the wild. 

The red-orange stigmas of the pale lilac flowers yield the Saffron itself.  These thread-like stigmas should be picked out as the flowers open and dried immediately in the sun or gentle heat, before being stored in the dark in an airtight container.  Some 60,000 flowers are needed to render and ounce of pure Saffron.  Fortunately, a few threads are necessary to yield a dish of color.  Crocus sativus is best grown from corms, the fleshy underground stem which resembles a bulb.  Although it can be grown from a seed, it will take three years to bloom.  The corms, which are available commercially, should be planted in mid summer in well drained soil in warm sunny location.