Penguin has a series called Great Food in which is Gervase Markham The Well-Kept Kitchen which is collection of excerpts from the The English Housewife (1615).

Advice is dispensed on keeping the kitchen garden.

In February, the new of the moon, she may sow spike, garlic, borage, bugloss, chervil, coriander, gourds, cresses, marjoram […] The moon old, sow holy thistle, cole cabbage, white cole, green cole, cucumbers, hartshorn, dyer's grain, cabbage-lettuce, melons, onions, parsnips, lark-heal, burnet, and leeks.
If the reader were to rely upon the Glossary one would be perplexed because :"hartshorn" is given as "the horn or antler of a a hart or wild deer". Used as a leavening agent as exemplified in the other instances of the occurrence of the word in the recipes. So what is this "hartshorn" that grows in the garden?

In the McGill-Queen's University Press edition, Michael R. Best gives one the following gloss:
A name given to several wild plants, most commonly Plantago coronopus, hartshorn plantain; the mystery as to why such a plant should be cultivated in the housewife's garden is solved by reference to Markham's source. In Maison Ruistique the plant is "corne de boeuf"; hartshorn is given by Cotgrave (1611) as the translation of "corne de cerf." "Corne boeuf" is translated by the more probable "herb fenugreek."
And ever faithful Wikipedia gives (bringing one away from fenugreek and back towards plantain)…
Le plantain corne de cerf (Plantago coronopus) encore appelé pied de corbeau ou plantain corne de bœuf est une plante de la famille des Plantaginacées.

Son nom lui vient de la forme de ses feuilles.
Which leaves find their way into salad: Rediscovered Salad Green: Buckshorn Plantain. By William Woys Weaver, Mother Earth News, April/May 2007.
The succulent, crunchy leaves are best when harvested young, and taste a little like parsley, spinach or kale, but sweeter and nuttier. The flavor is best before the plant begins to flower.
Does sound enticing.

And so for day 1475