The other night I picked some mint leaves, tore them up, and steeped them in boiling water. I call this ‘mint tea’. But is it really ‘tea’? Tea is made from the tea plant, Camellia sinensis. Spearmint is Mentha spicata.
How strict/pedantic are you in your definition of ‘tea’?
“Tea” without a modifier better be C. sinesis or heads will roll. With a modifier it can be anything you like. Sorta like “martini.”
Or “chili”.
flees
It also means “evening meal.” Which can be confusing when one watches British shows and hears “What do you want for tea?”
+1
I buy a lot of my tea from this ritzy tea shop, and they call their fruit and herb concoctions tisanes. But I still ask visitors if they want a “herbal tea.”
I have no problem with a tisane being called a tea, personally.
Yeah, you can call a tisane a “tea” in front of me and not fear a bone-crushing punch in the nose. I’m easy.
While I’m not terribly serious when I say it, I’m of the belief that if it isn’t C. sinensis, it shouldn’t be called tea. Hell, I barely consider decaffeinated tea to truly be tea. And never offer me tea and only have herbal/decaffeinated options. That’s just teasing.
That said, while I truly enjoy a premium tea, I’m certainly not a tea snob (as long as tea is brewed from fully caffeinated C. sinensis).
I drink tea, and I drink tisanes. If it comforts anyone, they may assume* that I am abbreviating “tisane” to “ti”* when I speak of steeped beverages which are not based on C. sinesis.
They may also assume that autocorrect does not recognize “ti” as a word, thereby further protecting their delicate sensibilities from the horrors of Descriptivism.
A drink with jam and bread
That will bring us back to Do (oh-oh-oh)
"You want the taste of dried leaves boiled in water?”
“Er, yes. With milk.”
“Squirted out of a cow?”
“Well in a manner of speaking, I suppose…"
-Douglas Adams
I can accept that. The use of ‘tea’ to mean anything but coffee steeped in water derives from the original drink, although ‘tea’ by itself for other varieties is often just shorthand for ‘something tea’ within context. Coffee is the only substance that tastes so horrible that it can’t be referred to as ‘tea’ in any manner.
Ginger tea is another good example. They make lots of tea/ginger combos, but in SEAsia ginger tea is usually made from just ginger. I often explain this distinction to guests after offering them ginger tea, as the one I make is just ginger, no actual tea!
To me, “tea” is an infusion of the soft parts (usually leaves, but occasionally blossoms) of C. sinensis in hot water, drunk as a beverage. Similar infusions of the soft parts of other plants are tisanes, not tea, and infusions of C. sinensis in cold water (or shudder supersaturated cold sugar solutions contaminated with such infusion, as is common in the South) are generally best not spoken of at all.
That said, I also recognize that very few other people recognize this distinction, and so I will grudgingly use the phrase “herbal tea” for the sake of communication.
It’s all tea to me. Today I learned a new word:tisane.
Not a desert-dweller, I take it? 
Tea is, properly speaking, an infusion of Camellia sinensis. However, in informal speech and writing the construction “herbal tea” is understood to be an infusion of something other than Camellia sinensis (which is technically a tisane). As I’m more interested in communicating with people than being a grammar/language Nazi I don’t worry about it.
Where’s the fun in that?
I consider tisanes a subset of tea.