Tea and Zen

This is something that makes a little more sense after you've had a lot of tea. You'll be able to tell the difference between a flat, not-complex tea and a complex tea pretty quickly if you try to drink a lot of tea, and a lot of variety. The photo is not mine, it was taken by a friend (whom I'm unsure wants to be named) while we were at the Tea Box in Richmond, London, UK.

Complexity will vary a little bit from person to person, but it typically comes down to the following:

• A noticeable or unique aroma, especially when you can taste the tea from the aroma alone
• Many tastes mingling together that makes it hard to pinpoint what exactly you're tasting
• On the flip side, many tastes mingling together where you can pinpoint what you're tasting
• The body of the tea (Is it buttery? Smooth? Bubbly? Rasping? Powdery? Full? Thick? Thin? etc.)
• Development of the tea over time (so from one steeping to another in both liquor and aroma).
• After taste + the unique flavors mingling 
• Length the flavor sits on your pallet

So, basically, it is very slippery and loose since it really depends on who you're talking to. 

Different teas fit my quota for "complex." For example, I love Japanese greens. They're what I'd call my expertise. A good Japanese green will always meet this. What the greens specific characteristics are will depend on if it is a shincha, gyokuro, sencha, or bancha. Very rarely banchas strike me as complex as they're an everyday tea, but that is besides the point.

Oolongs, good Sheng (that I've experienced so far), white, jasmine teas, many Chinese greens (especially Longjing!), and some blacks such as Darjeeling will also strike me as complex. This is a lot of variety, but I've had a lot of tea, and I enjoy many kinds!

While there are many wonderful black teas that I've had in the past, namely those from Yunnan, Laoshan Black, and Darjeeling, I find that many black teas are a one trick pony for me.

That being said, there have been more than enough teas from every other category that haven't been complex to me either. It really depends.

What's complex to me might be a one trick pony to another drinker, while a tea that is a one trick pony for me may be complex to another. Taste is very subjective.

Drink tea everyday. Drink a variety of teas that vary in quality. Compare the teas to one another if you can. Perhaps take notes on what you can figure out about the tea (even if it's just "I like it because it is sweet/fruity/woody/soft on my pallet" or "I don't like it because it is bland/sweet/fruity/woody/astringent" and simple notes like that) and before you know it you'll be able to tell a complex tea vs. a flat and bland tea, all according to your tastes!