Updated info: These are called "oak apples." They form when a paper wasp deposits eggs in a leaf bud. Early in the spring they are a beautiful light green color. Along the same lines as "Big Girl can't get out of the yard," comes "These came from the Sycamore tree." I swear I looked into the Sycamore and thought I saw things that looked like these earlier in the spring. Although I thought it was a might strange they were so far away from the host tree, I figured they are so incredibly light the wind carried them. Wrong again!