Whether herbal, black, or green, all tea is made from dried plants that will gradually lose potency over time. If you’re careful with storage and keep your tea sealed tightly and out of the light, it can last up to two years. However, if your herbs are exposed to air, humidity, light, or heat, they’ll begin to break down more quickly.
A simple way to check for freshness is by using your nose, which is actually a pretty highly refined chemical detector: Familiarize yourself with the scent of the fresh tea before it’s brewed. Then, if you’re ever unsure how old your herbs are, give the leaves a sniff.
If you do ever make a tea from old herbs, don’t worry: The result will simply be a boring brew. It’ll be a waste of time, water, and heat, sure, but not a big risk to your health.