With an end to the winter CSA season coming in two weeks (March 20), I’ll be sending out invoices via email and directions for payment in the next week or so. Stay tuned!
Solar power. The tree planting I mentioned last week continues here at the farm. This week, a jujube, medlar, pineapple quince, a few black locusts, and some osage oranges and kiwi vines are all going to be finding their way into the ground.
I’ve always been fascinated by trees, especially large mature ones. As a child I can remember riding in the car on that stretch of McLoughlin Blvd just north of Milwaukie, not far from our SE Portland pickup point. Does anyone know the stretch I’m talking about? The road parallels the railroad tracks there next to Westmoreland Park and passes under some massive oak trees that line both sides of the pavement. These oak trees are so large that they easily span the two lanes of traffic on each side, their branches intertwining above the concrete divider in the center of the roadway. The dense foliage blocks the light from overhead, and even during a bright summer’s day it’s dark in here. These trees are clearly old, and they haven’t visibly changed in the last 30 years or so, at least at the 40 miles per hour that most of us see them at.
As an adult, these trees are still fascinating to me. They are a testament. Not only to whoever planted them who knows how long ago and to those that have lived in the area a lot longer than I have, but they are also a testament to solar power.
I’m not talking about the solar power we usually think of when that term is mentioned in everyday use. The photovoltaic cell (that generates electricity and are becoming more popular around town these days) was only invented a few decades ago. The solar energy I refer to is much older, and microbes beat us to the punch of harnessing the energy of the sun by about 2.5 billion years or so.
When I was teaching introductory biology to college undergraduates I always really enjoyed the part of the semester dedicated to covering our understanding of how plants harness the energy in a photon of sunlight. For one, I really learned a biochemical process forwards and backwards that I had been introduced to and summarily forgotten in high school biology class, but also because it allowed me think much more practically about what this process means in the real world.
Photosynthesis is this process that plants figured out, and it allows them to create food (in the form of sugar) from water taken up from the soil and carbon dioxide from the air. We usually think of plants getting their food from the soil, but actually they just drink water and get their mineral supplements from the earth. The rest of their energy comes directly to them from the air around their leaves. This is true for all green plants, be them large oak trees along McLoughlin Blvd, the big leaf maple trees here on the farm or the radishes from our greenhouse that are destined for your salad this week.
A big bonus in this process of photosynthesis for trees is wood. Cellulose makes up wood and is created from the same food in the air, carbon dioxide. Wood allows trees to hold up their leaves to compete for the precious resource that is sunlight, and it provides a real physical manifestation of the process of photosynthesis, creating those stately figures in our landscape. Could you imagine a world without trees?
A couple of weeks after teaching undergraduates about the chemical steps of photosynthesis, I liked to pose to them the question “Where does the mass of a tree come from?”. This is a tricky question, and probably one that I wouldn’t have gotten if I was in their shoes. It was so tricky that usually only one or two people in a class of 30 or so got the answer that I outlined above. When asked, most students assumed that plants grew mass from material they took up from the ground, which in the face of things isn’t a bad guess since human beings only figured out how trees actually do it in the last two hundred years. Making the correct connection between the process of photosynthesis and the trees around us is one that I’d encourage all of you to make. Not only does it connect us with a fascinating piece of biology, it makes all the veggies in your share this week possible. It also provides a little piece of ‘how the world works’ trivia that you can use on others at cocktail parties!
As I mentioned earlier, trees seem to be such enduring fixtures in our landscape, even though they’re by no means permanent. They just tend to live so much longer than humans. But thinking of those giant oak trees along McLoughlin and remembering classroom exercises from years ago reminds me even more of the potential contained in each little sapling that I’m planting. I enjoy imagining them grow as I plant them and am looking forward to watching their carbon accumulate here on the farm for several decades to come!
Have a great week, and enjoy your trees (and veggies too)!