Excellent as a fundraiser as well as a Gardening activity
A novel twist on the 'Self portrait Tea Towel idea is to firstly Paint a large Teracotta planter with white emulsion.
Allow it to dry and then take finger prints from each of the children - use ink or paint. Once dry give the children a choice of pen to turn their print into a bug ~ Lady bird, Spider, Fly, Snail, etc !!
Write their name beneath it and again once dry use a quick drying varnish to protect the pot.
Don't plant directly into the pot though - as teracotta will absorb water and ruin the paint work
I'll try and get a photo of one .. but if you beat me to it & would like to share .. email
silky@silkysteps.com and Ill upload it for everyone to enjoy
Finger Print Bug Planters
& 
To go alongside it you could do more thumbprint bugs, cut them out, laminate them and attach to sticks for plant pokes. 
*shudder*
Linear Mode
