Humane Gardener

Thorny shrubs are a tree’s best friends. Enlist these and other plant partners to protect trees from browsing while still feeding an abundance of wildlife

The redbud seemed to appear out of nowhere, rocketing above other plants like a gangly teenager whose mother has to buy him new pants every three months. I hadn’t noticed the sapling before, probably for the same reason the deer hadn’t: it was surrounded by a patch of dense black raspberries.

Redbud surrounded by thorny shrubs of black raspberries — Above: Black raspberries created a refuge from herbivory for this young redbud. Featured image, top: Mostly turfgrass just a few years ago, this area of our habitat is filled with self-seeded walnuts, sumacs, and redbuds that sprout among the thorny shrubs.

Rubus occidentalis—or any plant in the Rubus genus—can be a tree’s best friend. In our habitat, these brambles form a protective wall around redbuds, black walnuts, hickories, tulip poplars, and other trees. The difference they make is hard to miss: In more open areas that lack these thorny protectors, some saplings of even supposedly deer-tolerant tree species don’t last long before landing in the mouths of our hungry mammal friends.

Deer in meadow — Deer are welcome in our habitat, where we nurture goldenrods, asters, sumacs, grapevines, sassafras, blackberries, black raspberries and many other suckering and spreading plants that they like to eat. For trees and shrubs less resilient to browsing, we employ strategies to protect them until they are tall enough to withstand some natural pruning.

Once I began to notice the protective effect of thicketing raspberries, I started seeing other plants providing structural refuge to trees too: A tiny sweet gum hiding under the broomsedge grasses. An oak tree sprouting near the center of a spectacular pokeweed. Staghorn sumacs wedging themselves between an Eastern red cedar and nearby beautyberries. A sycamore not afraid to show her face above the mountain mint.

Mountain mint and sycamore — Sycamores are less preferred by mammals, but small, tender ones are vulnerable when growing in isolation. This one popped up among clustered mountain mint, a species deer find unpalatable, and it’s old enough now to avoid being nibbled.

Sumacs and beautyberries — Staghorn sumacs used to grow in the low grasses in this space and were frequently browsed. Now that they’ve spread their roots between untasty beautyberries and even less appetizing Eastern red cedar, the deer aren’t interested in putting in the effort to reach them.

Even nonnatives can be nurse plants, something I had learned years ago when I found native groundcovers sprouting beneath multiflora roses. But now I was seeing opportunistic trees do the same. A walnut planted by a squirrel in a mugwort patch has grown into a 15-foot-tall tree, but only because the unpalatable herbs nursed the tree along in obscurity until it was old enough to stand on its own.

Walnut and pokeweed by bench2 — Two walnuts, one obscured at a young age by mugwort and the other hidden among black raspberries, have now grown tall enough to shade our bench by the pond. Between the walnuts, a glorious pokeweed is currently providing refuge to a young oak sapling hiding near its base.

Many of these tree species are considered resistant to browsing, and indeed they’re often ignored when something tastier grows nearby. But as houses continue to flip in our community and new neighbors indulge their turfgrass obsessions, the small, tender natives in our oasis are harder for local wildlife to resist. Shrubs and herbaceous plants often pay little mind to being nibbled here and there, sending out new roots and runners and seeds. Young trees can have a harder time, though, especially when planted (by me or squirrels or birds) in bare areas with few green friends to call their own.

Plants Need Friends Too

Rudbeckia and primrose — Lean on me: a brown-eyed Susan wraps around common evening primrose. We’re used to seeing wildflowers mingling, but trees and shrubs need companionship too.

Everyone needs companionship, including plants. Through their growth habits and chemistry, plants can protect each other from wind, sun, drought, flooding, and herbivory. They are just as invested in their communities as many of us humans are—and probably even much more so, given that they can’t just pick up and leave when the going gets tough. But as we’ve simplified our landscapes down to the barest, flattest geometries of a single groundcover punctuated by trees spaced widely apart in mountains of mulch, we’ve taken away plants’ opportunities for community and companionship (a concept I explore in more detail in my next book, Wildscape: Trilling Chipmunks, Beckoning Blooms, Salty Butterflies, and Other Sensory Wonders of Nature, due out in March).

Read a Q&A with Richard Broughton: Bring Back the Brambles!

Restoring these lost connections isn’t a matter of just imposing our own ideas of what nature should look like onto the landscape. Often the best way to bring back ecological function and natural beauty is to step aside and let the plants and animals lead the way. British ecologist Richard Broughton and his colleagues outlined some of the obvious benefits of “passive rewilding” in a study at Monks Wood National Nature Reserve in Cambridgeshire: This no-interference strategy preserves local plant genotypes that are best adapted to conditions of a given area. It decreases chances of drought-induced losses, as self-seeded woody plants are more likely to withstand extreme weather. It minimizes the risk of accidentally importing nonnative organisms hiding in the pots of nursery-grown plants. And a perhaps less appreciated outcome of passive rewilding—confirmed by Broughton’s research—is the natural caging that brambles and other thorny shrubs provide for trees like my redbuds and walnuts.

Allegheny blackberries are thorny shrubs that protect trees — Allegheny blackberry sprouted in the wake of my neighbor’s removal of two rows of pines. Deer browse the plant, but it just keeps growing, providing nesting habitat and berries for birds and small mammals. The dense habit of such brambles also protects tender plants in their midst.

In a matter of decades, animals and plants at Monks Wood recolonized two former agricultural fields lying adjacent to an ancient forest. First came the thrushes, whose droppings contained the seeds of blackberries (Rubus fruticosus) and hawthorns (Crataegus spp.), which quickly and thickly covered the lands alongside native roses and blackthorn (Prunus spinosa). Next came the Eurasian jays, wood mice, and American gray squirrels, all of whom likely planted pedunculate oak acorns (Quercus robur) among those thorny shrubs. (Score one for the squirrels, who are even less appreciated in England, where they’re considered invasive.)

Squirrel with walnut — As squirrels plant walnuts and acorns each autumn in my habitat, they’re also busy helping jays reforest former agricultural lands in England.

And then the hungry mammals, including native and nonnative deer species, showed up on the scene. But thanks to the safeguarding effects of thorny shrubs, the presence of brown hares, European rabbits, and native and nonnative deer didn’t prevent the new trees from growing and prospering. Other than the natural caging of the brambles, “there was no protection from browsing animals …” wrote Broughton and his coauthors. “Although herbivores can inhibit regeneration, they did not prevent rapid woodland and shrub development at our Wilderness sites.”

Rewilding the Humane Gardener Sanctuary

The sites in Broughton’s study were relatively small; one is about ten acres and the other half that size, or a little more than twice as large as the 2.25 acres of land surrounding our home. But the results show what might be possible if more of us banded together to rewild our yards into connected spaces: In less than 60 years, one of the Monks Wood patches has approached the height and structure of the nearby ancient woodland.

Context is everything, of course: At another passively rewilded area situated far away from forests, Broughton has found that the early successional shrub stage is lingering much longer due to the absence of tree seeds and some of their primary dispersers, Eurasian jays. Still, the Noddle Hill nature reserve is a diverse mixture of shrubland, wetland and grassland that buzzes with life and is treasured by other birds, insects and humans alike. Though often disregarded as “waste spaces” in both the UK and the US, thickets provide critical habitat to birds like willow warblers and turtle doves in Western Europe and woodcocks and brown thrashers in the US. Shrubs also offer critical floral resources for bees and other insects.

Bumblebee on thorny shrub flowers of Allegheny blackberry — Brambles and other thorny shrubs play numerous ecological roles. Their flowers are prolific and abundant at a time of year when bees are in critical need of pollen and nectar.

Here at the Humane Gardener headquarters, our habitat is always a work in progress and a research study in miniature, as we employ a combination of passive rewilding in some spots and active planting in others. Along the edges adjacent to mature woodland, we see new spicebush, sumacs, false nettle, ferns, oaks, walnuts, hickories, black cherries, red maples, flowering dogwoods, sweet gums, tulip poplars, pokeweed, Allegheny blackberry, black raspberry and sassafras. In the once-mowed field between, we’ve watched broomsedge, purpletop grass, beaked panic grass, and splitbeard bluestem move around the space for 20 years. Though still too open and eroded for many trees to take old, the evolving grassland has invited common milkweed, late boneset, wild senna, blue mistflower and a few other herbaceous species that provide a bonanza for pollinators but are unappealing to mammals. Added to the mix are tastier plants—Canada goldenrod, wrinkleleaf goldenrod, and frost asters—to sustain our deer and rabbit friends.

Caging trees in the absence of thorny shrubs — My beloved helper, Will Heinz, adjusts a cage on a young and tender hazelnut. Everything in the field around him—the boneset, yuccas, broomsedges, and purpletop grasses—was planted by nature.

When I find trees and shrubs out in the open and vulnerable to nibbling, I sometimes cage them—not to exclude deer permanently but to enable the plants to get tall enough to survive and provide more long-term sustenance and cover. As time allows, I also pull nonnative species that threaten to crowd out wildlife habitat.

Partnering with Plants and Animals

What would happen if I did absolutely nothing, though? A fair amount of research shows that, over time, the space could at least partially heal itself. I’ve certainly seen evidence of the beginning stages of that process here. But I also see the more immediate needs of animals already inhabiting this space: butterflies who’ve run out of flowers in our community, deer who need more twigs to browse, and birds and rabbits in search of the protective cover that thickets provide. So I do what I can to help these wild neighbors in their ongoing restoration efforts: the squirrels and chipmunks actively planting nuts, the deer and birds dispersing seeds through their wanderings, the moles tilling the soil, the voles spreading mycorrhizal fungi, and the bees transferring pollen from flower to flower. I watch the ingenious ways that plants persevere through drought and flooding and winds that would knock most of us down, and I try to avoid adding trees without also surrounding them with shrubs and wildflowers and other plant friends to grow up with.

Passive rewilding is not really passive at all, at least not from the perspective of the plants and the animals. They are the most successful restorationists, collaborating even as they compete for light and space and water. As the raspberries encircle the redbuds in thorny stems and the mountain mints safeguard the sycamore sapling in scents, I too will use whatever skills my species possesses—the power of observation, the capacity to learn from the experiences of others both human and wild, and the ability to integrate memories of the past and visions of the future—to give all these beings a chance to rejoin their communities, make a life here, and invite their friends to move back alongside them to this little patch, their ancestral home.

[Photos by Nancy Lawson]