The two are essentially the same – green tea leaves ground down to powder form. All malcha is powdered green tea, BUT not all powdered green tea is malcha.
Any type of green tea that is ground up can be qualified as ‘powdered green tea’. The green tea can be sun-grown, shade-grown, steamed, pan-fired, etc. As long as it is ground up into powder form, it can be called ‘powdered green tea’.
In order to qualify as ‘Malcha’, it MUST follow these rules:
(1) The green tea must be ‘Yeoncha’ (碾茶 – ‘tencha’ in Japanese). Yeoncha is made of tea leaves that are shade-grown (partially or fully), steamed and dried (some may roll or chop the leaves to make it easier to grind).
(2) The Yeoncha must be ground to a fine powder with a stone mill.