By Shana Hanson
Most livestock want to eat woody plants. Cattle, sheep and goats in Europe were historically wintered on abundant, tannin-rich forages; farmers dried tree leaves for sheep and goats, and ensiled leaves (stored anaerobically to ferment), or sometimes cooked or steeped dried leaves, for cattle and hogs. From 6,000 years ago until horse-drawn hay equipment became available, cutting branches was easier than cutting grass, and villages had many hands to tie sheaves or strip leaves.
Today, trees along pastures show a distinct browse-line, where cattle have eaten every leaf in reach — but farmers lack time to deal with leafy brush. Encouraged by ruminants, and by other farmers, I completed one farmer-led Sustainable Agriculture Research and Education (SARE) project, then dove into two more, to improve production methods, measure yields, and explore nutrition and utility of leaf-silage.*
Faster Leaf-Silage with Less Wood
Chipping makes brush more manageable. In 2018-2019, I fed chipped silage to cattle, sheep, goats and hogs at my 3 Streams Farm in Belfast, Maine, plus four other farms in Waldo County, for Northeast SARE Farmer Grant project FNE18-897. I used leafy branches up to 1 inch in diameter (yielding approximately 60% leaf and 40% wood). All livestock accepted the feed but preferred hand-stripped silage without the wood.
In 2020, Lucas Tree Experts (Maine’s largest roadside line-clearing company) did the harvest labor; large branch diameters raised wood content to 60%. (Foliar applications of herbicide along roadside powerlines have stopped; organic certification would require affidavits from multiple landowners.) Barrels went to three farms plus mine. Sheep at Y Knot Farm were the only ones to diligently sort through for leaves, needles and bark, and even sucked on wooden pieces, making them rounder.
I returned to hand-stripping, imagining various machines. I looked up logging equipment, envisioning a down-scaled chain-flail delimber. Karl Hallen, of Hallen Farm and the State University of New York College of Environmental Science and Forestry (SUNY ESF) Willow Biomass Project, created a prototype as the first step in our current pair of Northeast SARE projects (FNE22-013 and FNE24-083). The chain-flail leaf-separator quickly removes and collects intact tree/shrub leaves from large branches, and from trunks up to 3 ½ inches in diameter.
Last summer various helpers and I harvested enough leaves, of 13 common tree species and 10 shrub species present at MOFGA’s campus, Y Knot Farm and Faithful Venture Farm, to fill 77 thirty-gallon barrels. We heavily pruned most trees to resprout above browse height (making them pollards) and coppiced shrubs (felling them to resprout near ground level). Ten to fifteen lineal feet of field edge filled a barrel (contents averaged 52 pounds), and took three-quarters of an hour to two hours to cut, limb and stack, plus 10 to 15 minutes to run the leaf-separator per barrel. Gray birch took the most time per leaf volume; ash took the least. We slowed the feed speed and sped up flails for well-attached oak leaves.
After harvest, these stretches should rest for six to eight years before being harvested again, as our current machine prototype works best with large pieces of woody material. Three years would be the European minimum; in Norway, five years is considered sustainable.
Ruminants Want a Lot of Tree and Shrub Leaf-Silage
In winter trials, animals at four farms ate leaf-silage way faster than expected. Fourteen Holstein heifers at Faithful Venture Farm ate each barrelful of elm, oak, ash and locust in 20 minutes. At Tilden Pond Farm, the cow’s milk yield rose by about three cups per day when fed 7 pounds of poplar or honeysuckle leaf-silage per day in addition to her usual hay and grain. My 3 Streams Farm goats are grass- and browse-fed (no grain nor other outsourced concentrates); in non-leaf-silage control periods I fed precious second-cut hay in place of leaf-silage. Our winter milk production rose with the leaf-silage at the start of our trial, then stayed steady with a slight additional rise in control periods, probably due to higher protein content of that treat hay. My animals had unlimited first-cut hay throughout; it was harvested in late August and contained a lot of dead grass. (Due to wet weather, a lot of herds ate such hay this winter, with farmers grateful to have any.)
Scaling Up Harvests
Lucas Tree Experts and I have renewed collaboration; this summer, I’ll bring choice trailer-loads of their intact leafy branches to our leaf-separator, and I hope to line up a large chipper so that de-leafed trunks and branches will exit directly into it.
Can on-farm leaf harvest be scaled up, for easier organic certification? At the 2nd European Symposium on Pollarding, held in Sare, France in 2018, my French colleagues presented about mechanical tree canopy harvests from ancient pollards for community-based biomass energy. Small-scale European feller-buncher and chainsaw-type harvesters can likewise be used to produce livestock forage from rows of pollards. Such equipment beats the labor efficiency of my 9-foot pole chainsaw.
Large-scale field cropping of woody coppice beds is even faster, and offers ecological services beyond those of a hayfield. SUNY ESF willow plots are straddled every three years by the largest New Holland harvester, with a woody crop cutting head and Karl Hallen (the creator of the chain-flail leaf-separator prototype) driving. Dry matter yields are slightly above three years of hay yields. Karl and I plan to measure edibility of summer-harvested willow biomass chips; that answer will inform future work to divert the edible portion towards farms.
Nutritional Testing of Leaf-Silage
In 2020, a Vermont Grass Farmers Mini-Grant covered basic nutritional testing on leaf storage samples from SARE FNE18-897. Now SARE FNE24-083 is yielding in-depth nutritional data on over 100 leaf samples, including fresh and ensiled comparisons, plus data supporting cyanide toxin reduction in ensiled cherry. Gallic acid levels are thought to limit animal intake of maple species and sumac; we have found a lab to measure this. Animals much prefer Norway maple leaves to red or rock maple. Plant defenses match evolutionary experience; Norway maple probably let go of leaf defense since pollarded tops were kept out of browse reach, but it has highly defended bark to survive ever-present European livestock. Our striped maple is similarly tasty but lacks bark defense.
Nutritional tests do not measure tannins, which ruminants need in order to optimally digest and utilize proteins. Tannins in most common tree and shrub leaves have yet to be identified (in 6,000 years?). Instead, funding has supported bioengineering of leguminous crops (alfalfa, white clover) to produce tannins. Organic growers have been limited to (non-bioengineered) birdsfoot trefoil. Wayne Zeller, of the U.S. Dairy Forage Research Center in Madison, Wisconsin, has screened 23 woody species from SARE FNE22-013, finding especially high levels of condensed tannins in black locust, poplars and birches.
Yulica Santos Ortega, of MaineHealth Institute for Research in Scarborough, is looking at human health aspects of my goats’ milk produced with and without leaf-silage. Lipid profiles are consistently healthful, yet differ. The Betaine lipid DGTS is present in milk from both leaf-silage and control periods; among many benefits, this rare lipid helps creatures — us, and goat kids born in February — deal with cold temperatures.
I consume a lot of milk, so I am glad to know it’s healthy; and such nutritional information enhances the milk’s value to others. But ecosystem health matters even more to me.
Leaf Harvests Rejuvenate Trees and Trees Restabilize the Climate
My computer gets hauled on every goat walk to fulfill research commitments, plus I bring along and study scholarly articles about tree leaves and climate dynamics. My (mostly goat-driven) motivation is magnified by concern. I’m watching lifeforms closely as I sculpt my way through the tree canopy of the 3 Streams Farm woodland, and death seems to be escalating. Weather is becoming less regulated. Reduced emissions alone will not save us: The earth needs to be alive, to stay alive.
Water vapor from tree and plant evapotranspiration carries unfelt heat energy through time and space, to condense when and where heat and moisture are needed. We have stripped (and are continuing to strip) too much of earth’s climate-regulating ability. Trees create and moderate wind and rain, both locally on the farm and in more far-reaching ways. I’m recommending incorporating trees in “climate-smart” farm landscape changes.
Crop fields and pastures in Europe historically were sprinkled with pollards throughout. Lollipop shadows of such trees moved throughout the day with the sun. Both livestock and grass productivity peak at temperatures in the 60s; the shadows help.
Leafy canopy harvests rejuvenate and storm-proof pollarded trees, and deepen foliage, increasing habitat opportunities. Such harvests enhance drought- and flood-resilience of soil through carbonaceous remains of root die-back and regrowth, parallel to top-harvest cycles. This same root-cycling releases nitrogen to soil and nearby plants at each branch harvest; trees also routinely draw up moisture as needed and share with that ground layer. Fallen leaves protect soil in winter, feeding worms and fungi come spring. Leaves fed to livestock raise mineral content of manure.
We can create livable farm micro-climates. Picture maximizing farm-wide canopy density and foliage height diversity (the latter is used as a proxy for biodiversity measurement due to close correlation). Picture minimizing bare soil, gravel, pavement, roofs, solar panels and other inert or dead surfaces. Such surfaces lack fine-tuned environmental responsiveness and self-regulatory capabilities of live plants — and simply heat up when the sun hits.
As I open barrels of leaf-silage, people come close and breathe deeply to enjoy calming tree aromas. Trees on your farm release the same; the ruminants know.
Shana Hanson first climbed into fruit trees to prune professionally in 1983. She ascended to harvest tree leaves in earnest plus network internationally with pollard researchers in 2011, and presented at the 2nd European Symposium on Pollarding in Sare, France, in 2018. Upon her return, she began her first research project focused on “air meadow” canopy harvest in a mature woodland, trying an array of storage methods, and measuring palatability. Interested in learning more? Visit 3streamsfarmbelfastme.blogspot.com for information on tree leaf fodder and climate, plus links to all project reports.
*These projects are funded by SARE, which is funded by the National Institute of Food and Agriculture, U.S. Department of Agriculture.
This article was originally published in the summer 2024 issue of The Maine Organic Farmer & Gardener. Browse the archives for free content on organic agriculture and sustainable living practices. Subscribe to the publication by becoming a member!
