Caffeine is all over the map when it comes to tea. A typical rule to follow, and one that many people assume, is that black tea has more caffeine, while green and white tea have less. Although this is loosely true, many factors come into play to fully understand the caffeine content in your tea.

One of these factors is the concept of terroir. Terroir is the complete natural environment in which a particular tea was grown and produced. This includes a combination of soil characteristics and climate, as well as the timing and season tea leaves are picked. Culture is also included within terroir as this influences how tea is processed and how often it's picked. Research shows terroir affects caffeine levels in tea, and since terroir can vary dramatically (think certain growing conditions for wine grapes), resulting caffeine levels can differ wildly.

In Tea: History, Terroirs, Varieties (Marchand, et al 2011), 35 teas of varying types are compared for caffeine content.  The highest caffeine content is a black tea, seconded by a green tea. However, this same green tea appears again later in the list because it was picked at a different time of year. Two other teas appear twice with different rankings, each coming from different estates.

A general rule of thumb can be followed for choosing teas with different caffeine content. Caffeine content per 8 oz. (1 cup) servings are listed below.

• Black tea - between 60-90 mg
• Green tea - between 35-70 mg
• Puerh tea - a wide range between 30-50mg
• Oolong tea - a wide range between 50-80 mg
• White tea - 30-55 mg
• Herbal tea - caffeine free!

One tea outside this tea spectrum is matcha. Matcha contains the highest amount of caffeine (70 mg in 1 tsp) than any other tea type on the spectrum, because you consume the powder, rather than strain it like you would with green or any other tea.

Any tea comprised of tea buds, like Yin Zhen (also known as Silver Needles white tea), will also have a higher caffeine content. As mentioned before, these are loose guidelines. If you are seriously concerned, or need to monitor your caffeine intake, consider diving into your tea's origins to better inform your caffeine choices.

The takeaway is this: caffeine ranges dramatically in different teas and can never be absolutely pinned down, because terroir affects caffeine levels. Whether they are different varieties, undergo different processing methods, or are simply harvested at different times of year, all teas have different amounts of caffeine.