The Secret Life of Spring

Greening trees depend upon a web of life underground.

In early spring in the East our minds drift naturally to the treetops, as we eagerly await the soft wash of bright green—subtle as a watercolor stroke—that indicates the return of life.

Some trees, like this star magnolia, show off with early flowers.

Although it’s native to Japan, we have encouraged this specimen, thinning out competing shrubs and trees around it. It grows across from the front door just off the lawn, and as such it contributes to the more organized palette by the house.

But farther away, the property edges we’ve been rewilding interest me more.

Over the past few years, we planted hundreds of young native trees at Puddock Hill. Most went in as whips but some were as big as five feet tall. More than a quarter perished, and while the others are still young, their spring revival can feel like a miracle.

Where woods grow, the old tall trees challenge the young. “Let your sap run for a dozen years, decades more, a century perhaps, and you may aspire to my dominance in the canopy.” More than challenge. We now know that trees can help one another gather nutrients, fend off threats to the forest, even communicate, in a sense. “The wood wide web,” some glibly call it, but for the trees it may mean life or death.

Humans have long appreciated the importance of soil as a store of water and a provider of nutrients, but we only recently began to appreciate how truly alive it is—not just with insects and earthworms—and how interdependent are these living components. Perhaps we took so long to make the discovery because it all happens underground, hidden from us, and much of it is microbial.

In any case, as the soil at Puddock Hill grows soggy from the winter thaw and the spring rains, I try to imagine what’s happening down there. Roots pressing deeper into the ground, feathering out horizontally, supporting and in turn being supported by mycorrhizal fungi.

Last year, we had the great horticulturist Dr. Richard W. Lighty and his wife, Sally, over for cocktails. I have known Dick since his days as director of Mt. Cuba Center, where he was more instrumental than any other in converting the gardens to native plants. We were honored to have him visit Puddock Hill.

Drinks in hand, we walked our modest paths. When I observed that some trees planted at the same time and of the same height were growing at different rates, he said the development of the mycorrhizal network near each tree’s roots was the likely differentiator. In an example of convergent evolution, certain fungi and bacteria developed a symbiotic relationship with certain plants. As simplified for the layman in an article by a Harvard Ph.D. student, “Fungi can cover a large surface area by developing white fungal threads known as mycelium. Mycelium spreads out on top of tree roots by up-taking sugars from the tree and by providing vital minerals back to the tree, such as nitrogen and phosphorus.” Furthermore, “Certain species of fungi can facilitate tree resilience to certain environmental stressors such as predators, toxins, and pathogenic microbes that invade an ecosystem.”

On our walk, we also discussed what we’ve learned over the years about tree planting technique. Landscapers used to pride themselves on digging perfectly round planting holes with glazed edges, which often turned out to encourage roots to grow in a circle like those of a plant left too long in a small pot. The root-bound tree may appear to thrive for a while—even for many years—but eventually this limitation will catch up with it.

In many neighborhoods near our house, trees planted by contractors a generation ago are dying prematurely. If you look closely at where the trunk meets the ground, you can often see the problem, which manifests as knobbiness rather than a well-proportioned root flare. More dramatically, in a summer wind storm a couple of years ago, I saw a perfectly healthy-looking maple, maybe twenty years old, shear off at the soil line. Too much of that tree’s life was above ground and not enough below it.

We take the importance of wild soils for granted at our peril. In the Coachella Valley we recently had the privilege of joining a tour conducted by Michaeleen Gallagher, the director of Sunnylands’ Center and Gardens. The property, now open to the public, is the former winter home of the billionaire Walter Annenberg. Its stewards have dedicated themselves to pursuing sustainability (to some extent, at least; they still maintain a 9-hole golf course), and the gardens increasingly feature desert-friendly plants native to the Southwest. But it is still a garden, not a wild place. Michaeleen noted that the way the plants are massed in the garden does not reflect how they grow in nature, and in fact, despite attentive care, many plants die unexpectedly. She speculated that they are competing for micronutrients and minerals in the poor local soil, and some lose that competition.

When the band America sang that “the desert is an ocean with its life underground,” they spoke wisdom. And, desert or no desert, soil means everything.

The weather in the Southwest this winter was famously wet and cool. Folks who have lived in the Coachella Valley for decades told us it was the wettest and coldest winter in their memory. The hills in places are greener than they’ve been in a long time, but in other locations the super bloom is skeletal by comparison. Consider this shot taken in Tahquitz Canyon:

The slopes are lush with native shrubs and wildflowers (a few more pics below). Now consider how sere things look in this picture taken just days later along the Bump and Grind trail a few miles away:

The many variables that might account for this difference should be less significant after such a wet winter. I believe the main reason for the paucity of plants in the second photo can be found in the soil or lack thereof. Soils are generally poor in the desert to begin with, but in the second picture I suspect that much of the topsoil (such as it is) that would have nurtured a super bloom has eroded away, along with essential nutrients and other good stuff.

Back East, I like to think that our efforts as backyard stewards reforesting, rewilding, and planting natives will help the biome we don’t often see—the one below ground. If so, the trees we leave for posterity will be healthier and the spring canopy that much more green, the anticipation of future generations that much richer.

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Just a few pictures of the desert in spring bloom…

Native desert sand verbena (Abronia villosa), which often grows in the vicinity of creosote-bush but here was on its own:

Distant scorpionweed (Phacelia distans):

Emory’s rockdaisy (Perityle emoryi):