Spring is the time of young leaves. Nettle, dandelion and birch come first and are traditionally used for the spring cleanse, in folk tradition as a help to the body after winter.
Summer brings flowers. Chamomile, calendula, lime and elder flower one after another, each for a few weeks, and gathering is then most tied to the calendar.
Autumn is the time of roots and fruit. Rosehip, elderberries, comfrey root; the plant prepares for winter and sends everything down.
In winter we do not gather but use. That is when it shows how we dried and stored in summer.
Ašič's blends follow the same rhythm, though they are available all year: they are made from what was gathered in its own time.
This answer is general in nature and does not replace a visit to the doctor. The products are foods or cosmetic products and do not replace medical treatment.