Small Pines really long for the kiss of sunlight, so they spontaneously grow into Big Pines when they are in shadow at the end of a Season.
When playing with Pines, apply the following changes to the core rules:
Power Activation
This is the effect of the Small Pine Growth Power:
Small Pine Growth: Replace 1 Sprout treeple on your Planet board with 1 Small Pine treeple from the pool.
Special Rules
Before the Collect Light step of the End of Season procedure, all Small Pines that are in the shadow of something else must be replaced with Big Pine treeples.
Note: Only Small Pines that were in shadow before the Collect Light step grow up into Big Pines, not those that would become overshadowed only after a new Big Pine is placed during this step.