But two things are very different in the spring: it’s the xylem that contains the sugary sap, not the phloem, and there is no way, with the leaves missing, to ‘pull’ it up the trunk.  In addition, root pressure is not involved – pieces of living Sugar Maple stem by themselves, standing in water, can be made to create sap flow.

What does happen is linked directly to this specific  time of year, when nights fall below freezing and days warm above it.  Take away either of those conditions, and sap does not rise.  What happens is this.  First, in the fall, sugars are transported down into the stems and converted to starch.  In the spring, during the warm days, living cells convert that starch into sugar.  They also generate carbon dioxide gas.  This gas diffuses into the xylem.  As the temperature cools, the gas dissolves, lowering the pressure and pulling the sugary water from the living cells into xylem.  This water is replaced from adjacent cells, which form a conveyor belt for water down to the roots.  As night comes and the temperature drops further, water freezes along the inside walls of the xylem and in between its cells.  The remaining gas is compressed and locked in this ice.  Suction is created, which draws water from the soil into the roots.  With morning, things warm, the gases expand and force the now liquid sap up and out of the trunk or stem and into the tap.  As the day cools in the afternoon, the process repeats itself.  For more details, go here or here.  The process stops when the temperature remains above freezing and the buds begin to open.

Only a few trees besides Sugar Maples (distribution) contain the correct cell structure to produce this kind of temperature-related pressure, and include Butternut (Canadian distribution).  If you’re from much of the rest of Canada and feel like you’ve missed out on a childhood tradition, pout not -- syrup can also be made from birch trees (distribution), but the sap flow comes later in Spring and is dependent on root pressure.  Make your own!

Red Squirrels discovered this process long before we did.  They will nip at a twig to start the flow, then go away for a day or so to allow some water to evaporate and the sugars condense before coming back to consume the thicker sap.  It may have been an observation of this behaviour by indigenous peoples that led to their development of the syrup-making process. 

Related lesson plans and resources can be found here. 

Other Happenings:

• March is a month of weather extremes.  Keep track of temperature highs and lows, and compare the amount of snow received to the amount of rain (1 cm of snow is roughly equivalent to 1 mm of rain).  Here, temperatures can range over 50⁰C.  Test out the folk wisdom that if March “comes in like a lion”, it “goes out like a lamb”, and vice versa.

• The birds are returning, led by American Robins and male Red-winged Blackbirds.  Not only mark the first Red-wing, but check out where they are and what they do.  Do they go straight to the cattails?  When do males begin to call?  Where do they go in bad weather?

• Migrating Robins have already been spotted in areas experiencing recent warm spells. New arrivals are brighter and perkier than any overwintering birds (there’s one in Ottawa - what was it thinking?), but when do you know that your Robins have arrived?  The best way is to listen for their breeding call, which males will only use to establish and hold their territories, often early in the morning.  Of  several different Robin calls, only a few are territorial.  Report the first Robin you hear to the Journey North website.

• Migrating ducks will be returning to almost any stretch of open water.  Early in the month, look for Bufflehead (female).  Hooded and Common Merganser and Common Goldeneyes will return too, though some also overwinter in southern regions. Trumpeter Swans had made their way into our lake (Sturgeon) by late February. Get ready and brush up on your waterfowl ID skills.

• If you haven’t already repaired and cleaned out any nest boxes, it’s time to get to it before nesting activities begins.

• American Crows are already pairing and searching out nesting sites.  Males will fluff up their body feathers and bow repeatedly to the female (seems the food wins out in the end, though!).  Also keep an eye out for flying pairs, and stick carrying.  Do you have any pairs around your school?  Nests are generally built high up in evergreen trees.

• This is the best month of the year for owl calls.  Great Horned (now nesting), Eastern Screech and Barred Owls will vocalize, and will be joined by Northern Saw-whets passing through on migration.  Great Horned Owls don’t build nests, but rather use abandoned nests of other large birds, e.g. Osprey.  Here’s the adventure of one displaced hatchling.

• One of the first smells of spring, literally across Canada, (and much better smelling than skunk) comes from Balsam Poplar buds, where protective resin is softening in the warming sun.  Find some, pinch the buds gently, then smell your fingers.  The resin has medicinal properties, and if you can pick enough of them without impacting any one tree, you can make a salve out of them.  

• Taking up where his grey cousins left off, the male Red Squirrel can be seen chasing females through the trees.  Chipmunks may also pop up, shaking off the effects of their long, on-again off-again, winter’s nap.  Food is not the issue.  Mating is.

• Ice out, another rite of spring linked to biodiversity, may occur sometime during March on local lakes, ponds and streams.  Mark the date of your local water body for future reference, and report the information to IceWatch.

• Ever wonder where we sit in the bigger picture of the Milky Way Galaxy? Turns out we live on a minor spiral arm about half-way from the centre to the edge, keeping company with our friend Orion.                                                                                                            

• The James Webb Space Telescope, larger sibling of the Hubble, has been in place now for over two years and has produced some amazing images (scroll down).                                  

• The moon (scroll down) brushes by Mars on the 7/8th and Venus on the 8th. They may or may not be visible just before dawn from your part of Canada.