Many organic materials (wooden stakes, etc.) and most plastics can degrade over time to become illegible (either the written name or the entire label itself will crumble), so perhaps buying metal hang tags (they can be attached to short stakes so they don't have to be affixed to the plant itself) that can be embossed/stamped with plant names that won't weather off would be practical. Or maybe you could try something artistically creative, like painting labels on stone or maybe pre-painted bricks would suffice, though we don't have enough expertise to know how to weatherproof the different types of paint or if a primer is needed to coat the stone/brick first. We don't have data collected on this nor have we experimented with different materials in a direct comparison, so you could inquire with fellow gardeners in web forums or social media for additional ideas. Additionally, your county Master Gardener program might have tips or experiences to share regarding the suitability and longevity of certain materials; you could ask either at a plant clinic or ask the MG coordinator directly to poll their members for ideas.

Miri

Many thanks for your response.  I will try contacting MG’s, but since we will be working with school kids, I like the painted rock idea for them to do.

Kind regards,

Jane 

You're welcome!