when to pick catnip?

Answer 1

Just before the plant begins to open its flower buds. That is when the sap is at its strongest. Once the flowers open and bees start pollinating them, the oils start dropping off.

Answer 2

pick whole leaves in the early morning before the sun
has a chance to "cook" the smell out of them. dry in the
shade to keep them at their best.

Answer 3

the best time to pick almost every herb is in the morning just after the dew has dried