青竹 (green bamboo) i.e. fresh bamboo. In tea this usually means that it should be green and cut only a few days before an event. Ao take is traditionally used for futaoki (lid rests) when doing hakobi koicha or hakobi usucha and for hashii (chopsticks) for serving during kaiseki.
It is possible to keep bamboo looking fresh for some time by either:
- wrapping it in plastic wrap and putting it in the freezer.
- keeping it in water, but changing the water often.
It can be very difficult in our modern times to get ao take. Even in Japan you will have to order ao take a week or more ahead of time. It is possible to purchase imitation ao take; that is bamboo that is treated or painted to look like fresh green bamboo, but will not fade like natural bamboo. Imitation ao take is nice for keiko, but is not recommended for events like chaji.
Particularly interesting dried (white/yellow) bamboo futaoki are sometimes signed by tea masters or priests with their kao (a sign or symbol used much like a signature). These are acceptable substitutes for ao take futaoki. One may also keep the futaoki from your first event in furo season and use it again in October (last month of furo).