There are two ways to know that it is "officially" spring at the Arboretum. The first is when the snowdrops start blooming.
I always love it when the snowdrops are out because it is a sure sign that it is spring. They are the first flowers that I know to look for. They can push their way up through snow or survive when snow has fallen after they've bloomed. In "Stardust" Neil Gaiman noted their magical property. I can't agree more.
The second sign of spring is the tapping of the sugar maple trees.
There's nothing quite like fresh maple syrup. The Arboretum's annual pancake breakfast (which I missed for the first time in the last 4 or 5 years) is a great opportunity to indulge. And, the ways the trees are tapped is quite interesting, from the networked lines that interconnect dozens of trees to the singly tapped ones with bags. The conditions for maple tree sap to flow are very specific and only happen in spring (here's an article about it http://blog.lib.umn.edu/efans/ygnews/2009/04/the_mystery_of_maple_sap_flow.html).
All of these images were made today. It is nice that spring has arrived. Of course, last year I could get similar images on March 12, not April 26.