In Natural Playscapes: Creating Outdoor Play Environments for the Soul, Rusty Keeler writes:

“Childhood is supposed to be messy and and natural playscapes offer a kind of messiness that inspires learning and creativity. Children make mud pies out of mud; they pile up leaves and carry them around; sand and dirt are good for digging in. Two vital tricks are: having an extra set of ‘messy clothes’ on hand to change into and reminding parents to dress their children appropriately for play. If parents feel uncomfortable with the mess, tell them ‘the dirtier your child gets at school, the better reader they will become.’ When they scratch their heads, and look doubtful, explain that the experiences a young child has playing set up the foundation for future learning. The skills they learn on the playscape, such as having the confidence to try things they’ve never done before, will later translate to the school setting. For example, the world of reading…could seem daunting unless children have had positive experiences stretching themselves, gaining confidence, and growing through play. A natural playscape makes it easy for children to find challenging ways to dig, jump, stomp, and splash–and yes, get messy in the process–all on their way to becoming better readers.”