Bitterness that was chosen
Kuding’s Chinese name means bitter nail tea and it is drunk in southern China in hot weather precisely for that quality — the sweet aftertaste that arrives some seconds later is the reason people persist. Hops built an industry on bitterness. Wormwood gave absinthe and vermouth their names. Elecampane, gentian-adjacent European roots and Greek olive leaf are all drunk bitter by people with sugar available.
Bitterness that is a mistake
Chamomile brewed with boiling water for ten minutes goes bitter and loses the apple note. Chrysanthemum and honeysuckle do the same. Lavender at a spoonful rather than a pinch tastes of soap, which is a quantity error rather than a flavour. Almost all avoidable bitterness comes from three causes: water too hot, steep too long, or too much material.
What sweetening is doing
Every tradition that drinks hibiscus sweetens it. Greek mountain tea takes honey. Egyptian helba is sugared. Fenugreek, olive leaf and sarsaparilla are all bitter enough that the sweetener is part of the recipe rather than an indulgence. Judging one of these unsweetened is judging a drink nobody actually makes.
The pinch-scale botanicals
Lavender, wormwood, ajwain, hyssop, magnolia bud, lemon myrtle, kuding and elecampane all scale steeply enough that a teaspoon is a mistake. If a botanical has a reputation for being unpleasant, check the quantity before checking the supplier — the usual answer is that people are dosing it like chamomile.
Cold water changes the answer
Cold brewing extracts far less bitterness than hot, which is why Korean omija-cha is made in cold water over twelve hours and why sumac lemonade is steeped cold. Honeysuckle loses most of its bitterness cold-brewed. Where a tradition specifies cold, the reason is usually this rather than the weather.