The best time to harvest greenery for drying is when it is flowering. Drying greenery at this time will give you the best results. If you have a lot of greenery to dry, you can dry it in small batches. It is not recommended to dry a whole lot of greenery at one time because this may affect the quality of the dried plant. You can choose to dry some of your greenery at a time. It is not necessary to harvest all your greenery at one time.