On my way to the Arboretum for this report, I stepped into a glittery swirl of diamond dust. The diamonds were tiny, hexagonal-plate ice crystals, suspended in the arctic air and glittering over the ground.
I wanted to photograph the illusive crystals winking in the air. Instead, I caught a dog. A sundog is made of refracted ice crystals that flare along the 22-degree halo and disappear as the sun rises. These hexagon-shaped ice crystals are also the foundation of all snowflakes.
A sundog makes an appearance.
The presence of thin, cirrostratus clouds and frigid air bring on sundogs; and you’ll see them, too, if you are up early enough to be a dog catcher. With little moisture in the air, the low humidity feels dry and cold — the opposite of fog-frost when the air is filled with water vapor.
This season, meanwhile, there have been at least two events of fog-frost in the area, also known as rime ice, not to be confused with hoarfrost. Check the weather forecast or be on the lookout for dramatic shifts in weather. Diamond dust and fog-frost do not happen every day and can add a sense of wonder to your walk.
The March moon is the “sore eyes moon”’ on the Dakota calendar when warmer days melt the snow and cold nights refreeze it, making the surface hard and creating an intense glare during the day.
This cycle of warm days and cold nights also brings the sugaring season.
Indigenous Minnesotans set up seasonal camps near stands of sugar maple and birch trees to gather and process sap. Hollowed out maple logs or birch baskets held the sap, and hot rocks were cycled in and out of the containers as it changed from sap to syrup.
Sap flows downhill from the sugar maple trees to the Arboretum’s Maple Sugar House (left).
The same moon that creates snow-glare also drives the maple sap. The fluctuation between warm days and cold nights creates pressure inside the tree and forces the sap out of any wound (or tap) in a tree. Begin your walk at the Arboretum Maple Sugar House, located at the foot of a natural slope filled with sugar maple trees.
The sap travels by gravity and vacuum from the trees to the Maple Sugar House, through flexible tubing, to be processed. Syrup sweetness is based on a sugar-to-water ratio in sap, with silver maple, birch and walnut sap used with varying degrees of effort and outcome.
March 1 is meteorological spring and vernal signs begin to appear: Soon the early and shortest spring bulbs will start to emerge from the groomed gardens around the Oswald Visitor Center.
If you walk up the road a bit, near the front of the visitor center, a magnolia tree with buds that have been waiting all winter are wearing fuzzy coats. These coats are bracts with a fuzzy surface on both sides to keep the flower that has already formed, safe from winter's chill. Fuzzy bracts insulate some leaf buds, too.
Degree-day temperatures increase from 34 degrees to 49 degrees in Minnesota in March, filling the wetland around the Arboretum with flocks of red-wing blackbirds and all their summer allies. You will be trading your coat for a sweater soon.
Update: A recent storm of heavy, wet snow gave me an opportunity to capture fully developed snow crystals, stellar dendrites, up close on my clothing the following morning. Amazing!
Want to know more about snow? Kenneth G. Libbrecht, a North Dakota native, and physics professor at the California Institute of Technology (Caltech), invites you to visit his webpage at snowcrystals.com.