From oak trees to pine trees to palm trees to redwoods, National Arbor Day is all about planting and celebrating trees, both humble and majestic. And it turns out there's a lot to know about trees. For example, there are a lot of factors that go into how and why a tree might grow successfully. Nutrients, moisture, light, density, and "extreme conditions" all play a role into how and why a tree might grow (or not). And trees can grow in a ton of different environments, from sandy beaches to dense forests to urban areas.

Arbor Day is celebrated on April 28, so this Friday make sure to take a look up and appreciate the trees in your life! And for more ways to celebrate, visit the Arbor Day Foundation.

Image courtesy of Eric Fredericks under a CC license.