Herbs and flowers provide many health benefits for your hamster. Some contain a wide range of vitamins, some are good for the digestive system and some contribute to a strong immune system.
Some examples: Calendula is antibacterial, cornflower and chamomile are good for indigestion, echinecea leaves strengthens the immune system and dandelion leaves are high in vitamin A, B and C.
Enrichment:
In nature, hamsters spend a lot of their time foraging. Providing them with forage such as dried leaves, herbs, flowers and seeds will provide them with a lot of enrichment. They will spend a lot of time gathering it for their stash and the variety of different smells and texture will also provide them with an enriching and diverse environment in their cage.
How to store herbs, treats & flowers:
In order to avoid products expiring before they should, all products should be stored in airtight containers and the containers should be kept out of direct sunlight.
Many thanks to @hamstereducationandadventures - for writing this valuable and useful information.