Sejak (세작; 細雀; lit. "thin sparrow"), or dumul-cha (두물차; lit. "second flush tea"), is made of hand-picked leaves plucked after gogu (20–21 April) but before ipha (5–6 May). The tea is also called jakseol (작설; 雀舌; lit. "sparrow tongue") as the tea leaves are plucked when they are about the size of a sparrow's tongue. The ideal steeping temperature for sejak tea is 60–70 °C (140–158 °F).
It depends not only on the processing method the tea producers use, but also on the cultivation practices the tea growers use. What time of year is the tea plucked? How is the plant pruned? What parts of the plant are plucked? Are the plants treated with chemicals or are they organically grown? What kind of heat is applied to the tea leaves to stop oxidation? How are the tea leaves shaped, rolled and dried? Are the leaves left whole or cut in smaller pieces?
Shade grown: All matcha is made from shade-grown tea leaves—a labor-intensive process where tea bushes are protected from the sun and light is filtered to the bushes in a very controlled manor. Shading boosts the chlorophyll production in the plant, giving the leaves a rich green color. The lack of sun reduces the plant’s photosynthesis of the leaves, which in turn alters the naturally occurring levels of caffeine, flavanols, sugars, antioxidants, and theanine. By controlling the sun exposure, tea producers can significantly alter the chemical make-up and flavor of the final tea leaves.