Interested in agroecology and applying its transdisciplinary lens to local farms and issues? Please consider our summer graduate course PSS 311: Introduction to Agroecology. This course can be taken as a stand-alone or as the first course of our Certificate for Graduate Study in Agroecology (CGSA). We also offer it as a non-credit option, which, in addition to students, draws professionals and practitioners working in the field. This brings together a diverse community to learn and share different perspectives and experiences. If you have any questions, please contact Emily Harrington (agroecol@uvm.edu).
Surprisingly, it’s the opposite, but this winter is a long ways from being worrying.
All temperate climate plants go through a period called dormancy, a mandated winter rest. This is triggered in the fall by not only temperatures, but by day-length. As the days get shorter the plants go through chemical and physiological changes to prepare for below normal temperatures. Once dormant, the plant needs sustained cold (500-2000 hours below about 40 degrees) to break dormancy and get ready to grow again in the spring. So, if this winter were to have stayed above about 50 all winter long the plants wouldn’t have started to grow, but the opposite, would just sitting there doing nothing.
And this makes sense. I’m always amazed at how smart and resilient plants are. While this winter is fairly unusual in the sustained warmth, we do see warm spells most winters, and plants that would start to grow at the first blush of spring wouldn’t be around very long. Breaking dormancy requires not only warm temperatures, but increasing day-lengths, longer spells of sunshine to break their winter gloom.
What can hurt a plant is freezing temperatures once dormancy is overcome. In trees, this is seen as frost cracking, long vertical fissures in the bark caused by water freezing in the xylem after warming up and moving around in the daytime. (Look at the trunk of the Sycamore in the triangle in Wilson Terrace outside McCullough)
This adaption to day-length also explains why plants with a local background (called provenance) is best. Day-length varies by latitude, with greater variation seen in northern latitudes. Take a tree from Vermont, move it down to Georgia (poor thing), and it will stop growing mid summer, as the days are a northern fall-like short. What I see quite a bit more, though, is the opposite. Plants grown in a nursery down south and moved up north don’t know when to shut down and start dormancy, and are often growing late into the fall, with their leaves and twigs freezing, unprepared for winter.
And while I’ve got your attention, let me take care of one final question I’ve been getting. No, your lilacs aren’t ‘budding’. Many people are looking at their giant buds on the ends of the lilac twigs, and think they are swelling about ready to pop and start growing. They were actually that large this fall, you just were too busy looking at fall foliage. Fear not.
Professor Jeff Byers wrote last weekend-
I don’t know if there is anything you can (or would) do anything about, but there is an oak tree between BiHall and Coffrin that was in the process of being totally devoured by gypsy moth caterpillars! There were so many that I could hear the hum of their munching under that particular tree.
I went right over. (the joys and perils of instant email on my phone-it was a Sunday.) I was terrified it was the giant Pin oak tree, the one that made the list of the twelve oldest trees on campus. Fortunately, it was one of the Poplars nearby. And was I impressed.
I couldn’t hear the munching, I think they were all fat and lazy by the time I got there. Much like me on a sunday. Not Jeff-have you read his blog? The last time I did a trail run up the wrong secret side of Snake Mountain I came down with Strep. I reached up to one of the many defoliated leaves, and grabbed a caterpillar.
Bugs don’t freak me out, snakes do.
Jeromy Gardner, our elm guru from Bartlett Tree in Manchester, correctly identified it as Satin Moth. Not worrying, but has a habit of building a large population every so often and completly covering a tree, in this case our White Poplar. Here’s a great article, if you are interested. They were originally thought to only attack exotic poplars, such as Lombardy poplar and European White poplar (what ours is), but now also is seen in forest stands, and could become significant if defoliation occurs for several years in a row. It does, however, have plenty of natural enemies, including parasitic insects, bacteria, fungi, even birds.
Satin Moth-moth phase.
Photo courtesy Perry Hampson, Bugwood.org
So all that remains on the tree are the major veins of all the leaves, everything in between them eaten. I fully expect the tree to re-leaf in a couple of weeks or so. What is even more interesting is the other white poplar about 30′ away, with only a minimal population. The infested one was in a construction zone a couple of years ago. Maybe the stress of root compaction has something to do with this? Or I’ll be writing about both trees being infested next year…
Skeleton-ized tree.
Thanks to Jeff for pointing it out. Maybe I’ll host a ‘trailrun’ of the trees on campus someday this summer. Better start training now.
As you may well be aware, the Emerald Ash Borer is a small exotic insect invading the country, and is poised to enter Vermont in the next couple of years. It has the potential to eliminate all the native Ash trees from the state. Just on the campus grounds itself we have over 200 large Ash trees that will need to be removed at great expense, and replanted. For a quick explaination, see http://www.vtinvasives.org/invaders/emerald-ash-borer .
Two years ago my winter term class took a draft of an emergency preparedness plan for the eventual arrival of the insect from the State Department of Forests, Parks, and Recreation and completed it for the Town of Middlebury. This winter term we are now drafting the plan for Middlebury College. This includes surveying all the Ash on campus, coming up with options for treatment or removal, giving replanting options, and running a computer model to calculate the lost benefits from these trees, including stormwater and pollution abatement, carbon sequestration, and energy savings.
We’d be honored if you could join us to present the plan to the College community on Wednesday, January 28th at noon, in The Orchard, room 103 in the Franklin Environmental Center. I understand it’s short notice (sorry!) and winter term is crazy in even a relaxing year. Please feel free to email me with questions, and if you know of someone else that would be interested, please let them know!
In a wonderful book I’ve written about before by Nalini M. Nadkarni called “Between Earth and Sky-Our Intimate Connection to Trees” she writes of how botanists and tree physiologists have been looking at how sap is produced within maple in the last couple of decades. Like many things, the wild world of maple syrup seems like a freak chance, a perfect random combination of physiology.
A tree’s goal, aside from reproduction, is to feed itself-it’s tough being an autotroph, and a whole lot of work. Photosynthesis takes place all summer long, making sugars for respiration, growth, reproduction, and a little extra. This extra, in a sugar maple, gets stored as starches within the sapwood of the tree. The sapwood, as the name sounds, is the area of the trunk and branches where water and sugars move around, located within the first couple rings of the wood.
As my winter term class hopefully remembers, Sugar maple is one of our “live slow, die old” species of trees. These trees are more shade tolerant, in life for the long haul, and have the foresight to save extra sugar for lean times, such as the introduction of shade or competition. Other tree species, such as Poplar, live fast and die young, and burn through all their sugar like a hyper 3 old, just as prone to growth spurts as an Aspen in the spring.
Early spring brings sun, a little higher in the sky, and better able to warm. Cats in our house know this, moving away from the woodstove and into little patches of sunlight on soft surfaces. Trees know this too, as the sun warms the bark and the wood. The air may be below freezing, but tree surfaces and interiors could be well above freezing. Once the wood gets to be above 40 degrees, enzymes turn these stored starches into sugars, mostly sucrose, and the sugar is now within the sap. This explains the magical sugaring temperature of 40, any warmer and this process stops.
The other freak chance miracle of maple is getting the sap flowing out of the tree. Not all trees can do this. Water is moved throughout the xylem of the tree by capillary action and transpiration, meaning the leaves need to be on the tree for water to move very effectively. That would ordinarily make for tough sugaring in March and April, except in Maple.
In maple trees the space around the wood fibers is filled with gas, not water like most plants. When the temperature drops, this gas contracts, making space for the sap laden with sugar in between the cells. So water can move upwards from the roots by capillary action without the benefit of transpiration from leaves. This water freezes at night between the cells.
The day brings warm temperatures, melting this ice and expanding the gas, forcing water down the branches into the stems and trunks of the tree. The taps put into tree trunks to collect sap pierce the xylem all this sap is moving through, and water flows down the tap into the bucket or plastic line.
Interested biology students should read another blog, The Botanist in the Kitchen, http://botanistinthekitchen.wordpress.com/2013/03/18/maple-syrup-mechanics/ , and a cool roadtrip would be the Proctor Maple Research Facility of my old school UVM.
The landscape department, working with the State of Vermont, the US Forest Service, and a local researcher from UVM (Dale Bergdahl, father in law to local Middlebury College hero Mike Kiernan) applied for and received a grant from the Vermont Department of Forest, Parks and Recreation to erect the fence to grow Butternut trees. Butternut is threatened by Butternut Canker, a fungus with the potential to wipe out all Butternut across the United States. When found, disease resistant trees are grafted and grown for seed. An orchard was already established in Brandon, but another in a different locale (geographical as well as horticultural) is always preferred.
Deer love young butternut trees, hence the fence.
I’ve written a large explanation on the project on the blog here, it’s an entire page-Butternut Seed Orchard. I should give profuse thanks to Barbara Schultz, the forest health program manager in the Vermont Dept. of Forests, Parks and Recreation for an immense amount of work to make it possible, Chris Casey of the US Forest Service and Tom Simmons of the Vermont Dept. of FPR. And also, most importantly, local volunteer Sally Thodal for helping plant Butternut trees on one of the hottest days of the year.
Feel free to email any questions you have, and say hi to the trees as you drive by.
