How long does tea stay fresh? Where to keep it, with a freshness checker

Tea does not go off like milk. A dry, sealed leaf can sit for years without becoming unsafe. What it does is go stale: the aroma thins, the colour dulls and the cup tastes flat, like a spice jar you bought three moves ago. Whether that takes six weeks or two years depends on the kind of tea and on four things you control: air, light, damp and smells.

What actually wears tea out

Dry tea leaf is a sponge for its surroundings. Each of these does a different kind of damage:

• Air. Oxygen slowly changes the leaf and lets the fragrant aroma compounds drift away. Green tea shows it first, as browning and a hay-like smell.
• Light. Strong daylight breaks leaf down, so a clear glass jar on a sunny shelf looks lovely and does the tea no favours. Opaque is better than clear.
• Damp. Moisture is the only thing that makes tea unsafe, because wet leaf can grow mould. It also dulls flavour long before that.
• Smells and heat. Tea picks up odours easily, so keep it away from spices, coffee and the cupboard beside the hob or dishwasher. Steady cool temperatures beat warm kitchens and daily swings.

How long, for which tea

The two ends of the scale are matcha and black tea. Matcha is a fine powder, so a huge amount of surface touches the air, and an opened tin is at its best for a month or two. Whole-leaf black tea and darker oolong are already oxidised and hold their character far longer, with aroma fading slowly over a year or two. Green and white tea sit in the middle, at roughly three to six months once opened. Herbal blends full of dried flowers and fruit lose aroma faster than leaf tea. Pu-erh is the odd one: it is meant to age, so it is kept at steady room temperature and moderate humidity, not frozen in time.

These windows are rules of thumb from tea sellers and producers, not lab measurements, and different sources give different numbers. Use the tool as a guide to when to start paying attention, not as an expiry date.

Is it stale, or is it spoiled?

Stale tea smells faint, looks duller and tastes thin. It is safe. Mould is the line: fuzzy spots, a musty or damp smell, or leaf that has clumped from moisture means it goes in the bin. Dry leaf stored sensibly almost never gets there.

The fridge question

Fridges are tempting, but they come with a catch. Every time you open a cold container in a warm room, moisture condenses on the leaf. Producers do keep unopened green tea and matcha cold, because the sealed pack stays dry inside. Once a pack is opened, keep it in a cupboard instead, and if you do take an unopened pack out of the fridge, let it come up to room temperature (a few hours, longer for a big tin) before cutting it open. Do not refrigerate black, oolong or herbal tea at all.

Tea stays safe for years and tastes its best for months. Keep it dry, dark, sealed and away from smells.

What to look for

• Opaque and airtight. A metal tin with a tight lid or a foil pouch pressed flat and clipped shut. Clear glass only if it lives in a drawer.
• Right-sized. A tin you fill, not one that is three-quarters air. Buy matcha and green tea in small amounts you will finish within a couple of months.
• Away from heat and smells. A cupboard away from the hob, kettle, dishwasher and spice rack.
• One tea, one tin. Strongly scented teas such as smoked or flavoured blends will share their smell with anything beside them.