My daughter showed me the following idea on a Montessori blog. I cant remember the blog name so made the planters from memory. I have saved milk cartons,washed them and removed the labels.
I then cut away part of the carton
Found two pieces of wood which I painted white
Then slid the cartons onto the wood, I will need to make a few small holes in the bottom for drainage.
I have made two rows of planters to take down to the twins this weekend. I will take compost and get some seeds for them to plant and then Daddy can hang them on the garden fence.