Happy Earth Day and Michigan Native Plant Month! This morning I got to see a live webinar by Nancy Lawson, the Humane Gardener, an author and inspirational gardener and explorer. If you are not familiar with her work, check it out. She has an unconventional way of looking at things that takes my breath away in wonder.
I always learn a lot from her talks, but for this quick post, I want to focus on how she connected the dots for me on several reasons to leave the leaves. Some of these ideas are things I learned from her presentations and website, and some are scattered more widely across the information-scape regarding native plants, but I've never seen them consolidated in a post. You will see the standard singe-issue memes on social media about "leave the leaves until nighttime temperatures are consistently 50 degrees" or "don't cut dead stems until the insects hatch out" but there is so much more to accepting "dead" material in our landscapes.
There is no time limit on the usefulness of dead material
Yes, bees nest in hollow stems, and many will have hatched out once the weather warms, but what about next year's bees? As soon as this year's bees hatch, they find mates and begin excavating and provisioning a nest tube for their own young. If you pick a date when nighttime temperatures are consistently 50 degrees, as popular native plant wisdom advocates, you are wiping out next year's bees. The dead stems from last year need to stand through this year and into next year in order to ensure bees for next year. By that time they will be falling over and decomposing on their own, right in the place they are meant to be. There are other decomposers and soil microbes that need the nutrients in those dead stems and leaves exactly where they are in your flower bed, under the freshly growing plant. Meanwhile, this year's growing stems will be the home for next year's bee larvae.
In the fall, countless creatures will need the leaves and stems in place to take shelter from the winter. Insects are living their whole life cycles in those leaves and stems and from their perspective (and isn't that the point?) there is no time when it is good to "clean up" a garden. If you feel you must tidy up (and really, why?), cut as little as possible and drop it under the plant to compost in place. However, Nancy Lawson's presentation this morning showed a dead stem with a seed head, perhaps from a goldenrod. A tiny spider had woven it all about with a web, and an equally tiny bee was using the ball of dead seed stems and spiderweb to conceal and defend a nest tube lined with bright yellow flower cutouts. If the homeowner had trimmed that "ugly" dead seed head from last year's flowers, neither the spider nor the bee would have a home this year. Instead of just clearing the way for this year's people-pleasing flowers, leaving the stems allows the beauty of observing the complicated dance of life contained on the dead stems.
Dead material has more life than we see at first glance
Like the spider and the bee above, countless creatures are using the leaves and stems as their own little landscape. They hide from predators, search for food, make nests, and spend the winter in curls and crumbles beneath our plants. Or, they rise above it all spinning webs, catching aerial insects, and avoiding ground-level predator traffic by using last year's stems. The dead material is infrastructure for these little habitats. When we clean up with rakes and blowers it is like a hurricane wiping out a town.
When I was growing up, my family, like most families, took pride in raking up every single leaf. Fortunately the leaves were dumped on the edge of our woods several hundred feet away instead of being landfilled or burned, so there were a few survivors, but countless spiders, bees, moths, and butterflies were removed from our yard. From the perspective of these creatures, this was an annual annihilation of habitat. One year, life got in the way of the intensive annual cleanup. The following spring I saw my very first Brown Thrasher. The charismatic but shy Brown Thrasher is adapted to hunt in a "dead" landscape of leaves and stems. They literally thrash through the fallen leaves looking for snacks - flushing tasty insects, plucking fallen berries, and exposing worms. We accidentally created a habitat for a Brown Thrasher simply by not raking under our forsythia bush for one single year, leaving the leaves and all they contained.
Dead material stores resources
Plants spent all season turning water, nutrients, and energy from the sun into sturdy and chemically complex leaves and stems. Their value does not end just because the plant is done using them to process energy and reproduce. Squirrels and chipmunks use these materials to line and insulate their winter homes. Birds will collect them in the spring to make nests. The leaves and stems will break down and enrich the soil, feeding next year's growth. But there are uses for these dead materials that go beyond the structural.
Nancy Lawson observed Monarch Butterflies "feeding" on dead stems of certain native plants. After investigating, she discovered that they were gathering chemical compounds from the dead plant material. This had been observed in other butterflies, as described in her June 26, 2021 article MONARCH RX: CALLING ALL BUTTERFLY WATCHERS:
"a 1983 paper by Michael Boppré that explained it: Many clearwing and milkweed butterflies gather pyrrolizidine alkaloids (PAs) from dry or injured leaves for use in male courtship, pheromone production and defense. They do this by first applying a fluid from their proboscises that will dissolve the PAs into a liquid they can imbibe."
The butterflies sought out and spent significant time on dead stems containing chemicals they appeared to need. This behavior had not been previously documented in Monarchs, and Nancy Lawson's observations raised many questions, not the least of which was: why had this not been previously documented? She hypothesizes that in our managed landscapes in the US, there are few opportunities to observe butterflies utilizing dead stems because we are so quick to remove anything dead and brown.
My take-away is that our understanding of the relationships between insects and native plants is so limited, we can't assume a plant is useless just because it is no longer green and colorful and useful to us. Dead stems and leaves have purposes beyond what we can see. We should leave them to fulfill their role, and we should watch and learn.
Brown is a color
This is a phrase I have repeatedly heard from smart and funny landscape designer and author Benjamin Vogt. (If you don't follow him on social media, you should.) We are conditioned to see colorful gardens in magazines and webpages in full bloom. Plant lists let you select plants by spring, summer, and fall bloom time. But what about winter? This question should be of utmost importance to us in the U.P.! We are going to be spending far more time looking at our plants in their winter garb than summer. I suppose the traditional technique of cutting down everything in the fall and sending it to the compost facility solved the problem by making the landscape flat and empty in winter. But, that method steals the overwintering site of insects, winter seeds and perches for birds, and shelter for some of our more fun winter birds like grouse. Plus, it's boring.
I would much rather watch finches pluck seeds off goldenrod while chickadees excavate goldenrod galls for larvae than stare at snow for as far as the eye can see. Little Bluestem is absolutely gorgeous in the winter, with reddish stems topped with silver seeds. If you want some serious red to break up the lack of winter color, check out the crimson stems of Red Osier Dogwood. But in the flat gray and white of a U.P. January, I am happy just to have the tan stems of Early Sunflower, or the rich browns of Joe Pye Weed adding earthy tones to the landscape.
And texture! The bareness of the winter really lets you enjoy the arching branches of Ninebark, or follow the winding path of Woodbine over a log. Some plants stand tall in even our worst winter snow - Yarrow, Smooth Blue Aster, Gray Goldenrod, Swamp Milkweed... Our collection of plants with winter interest is Here. Their structure and muted colors are little lighthouses of promised life in the frozen landscape. Come February, brown is definitely my favorite color.
So instead of tidying up the garden in honor of Earth Day, how about tackling some invasives, killing some grass for a future planting (don't forget to use coupon April23 before the end of the month), or just sitting back and observing all the life abuzz when you leave the leaves.