Culpepper can help!
Culpepper's Complete Herbal
Hemlock: …The whole plant, and every part, has a strong, heady, and
ill favored scent. Hemlock is exceedingly cold, and very dangerous,
especially to be taken inwardly.
Hellebore (Black): …It is an herb of Saturn, and therefore no marvel
if it has some sullen conditions with it, and would be far safer,
being purified by the alchemist than given raw… ;also being beaten to
powder and strewed upon foul ulcers, it eats away the dead flesh, and
instantly heals them: nay, it helps gangrenes in the beginning.
Hellebore (White). The roots are thick at the head, white on the
inside and very full of fibers all round, of a hot nauseous taste.
Like the former it is it cold Saturnine plant, and possesses but to an
inferior degree the virtues of black hellebore.
Foxglove: the flowers have no scent, but the leaves have a bitter hot
taste… the urban is familiarly and frequently used by the Italians to
heal any fresh or green wound, the leaves being but bruised and bound
thereon… I am confident that an ointment thereof is one of the best
remedies for a scabby head.
Nightshade (common): the whole plant is of a watery and insipid taste,
but the juice of the berries is somewhat viscous, and of a cooling
and binding quantity. Be sure you do not mistake the Deadly
Nightshade for this.
Nightshade (deadly): … berries of the size of cherries, black and
shining when ripe, of a sweetish and mawkish taste. Only a part of
this plant has its uses. This Nightshade bears a very bad character as
being of a poisonous nature. It is not good at all for inward uses…
Aconite – we have many poisonous aconites growing in the fields, of
which we ought to be cautious: but there is a medicinal one kept in
the shop; this is called the wholesome aconite; anthora, and wholesome
wolfsbane… a decoction of the root is good lotion to wash the parts
bitten by venomous creatures but it is not much regarded at this time,
and should be cautiously kept out of children’s way, for there is a
farina in the flower, which is very dangerous is blown in the eyes;
the leaves also, if rubbed on the skin, irritate and cause soreness.
Culpepper's herbal was written in the mid 1600s. He goes on at some length about each plant in his very lengthy (I would estimate 1000+ entries) reference work and for the majority he includes a sentence on flavor and odor. I have pasted these here. They are not thorough but I feel confident they are correct.
His work includes only herbs he considers to have medical application - oleander, for example, was certainly known to him but does not appear. Some seem unjust; dill for example is said (in comparison to fennel) to have a "stronger and unpleasant scent". !!
It is worth noting that an assassin might not only use potions, but also blown powders, poison daggers etc. Also a contest would include other herbs as well to keep people guessing.
