If you gather the herbs at the right moment, they can unfold their power a lot better. The drying is easier and they will not mold.
If you plan to store the seeds, it is recommended to use the ascending moon (Sagittarius, Capricorn, Aquarius, Pisces, Aries, Taurus). There is however an exception - you should rather avoid days in Capricorn and Pisces. Quite beneficial are fruit days (Aries, Leo, Sagittarius).