May’s Tree of the Month: Monterey Pine

On the historic East Campus of Cypress Lawn Memorial Park, two towering Monterey pines overlook many monuments and memorials, the carved testaments of lives we continue to celebrate and remember. This pair of pines may be the grandest specimens of Pinus radiata standing today at Cypress Lawn — a living legacy of the timeless connection shared here between people and trees.

A tree is a versatile metaphor for life itself — indeed, examples of this are scattered across our cultural history as a thousand leaves upon an autumn lawn. From the tempting fruits of Eden to the meditative enlightenment of Siddhartha Gautama beneath the sacred Bodhi tree; from the shrouded mystery of J.K. Rowling’s Forbidden Forest to the gentle courage of J.R.R. Tolkien’s stewardly Ents; from Robert Frost’s woods, “… lovely, dark, and deep” to Shel Silverstein’s “The Giving Tree.” As a symbol and keen representation of our innermost nature — the light and the shadow — trees have long stood with us.

It is no small wonder then, that all around the world, our cemeteries — where the stories of human life are etched upon the earth — are also home to a great diversity of the world’s silva. In the urban environment, certainly, there may be no better place to find a collection of grand old trees than amongst the headstones. The living specimens within Cypress Lawn’s Arboretum would assuredly not define the landscape of Colma — as they have for over a century — were it not for the “everlife” they represent, a spirit that helps us feel resolve in saying farewell to the people we love. The trees aid us in celebrating the life that leaves us, and each time we return to say hello, their stable presence is an assurance that our ancestors truly do rest in peace.

This symbolic connection between people and trees is a kinship we all share, whether or not we are mindful of it each day. In the month of May, as we all step cautiously forward into the uncertainty of tomorrow, I would like to take a moment to share with you the story of a tree I hold dear, whose life is rich with meaning and message for us to know and to help us through.

This sequential illustration demonstrates the way of life, the natural history, of the Monterey pine. Beginning in youth, a rapid maturation of this species allows for serotinous cones with 100 or more seeds in each to grow in the tree canopy within only a couple of short decades. This fire-obligate seeder is evolved to then depend upon a major fire event to reproduce, opening the cones and sending many thousands of seeds out into the landscape. In the ashen aftermath of such a natural process, the rebirth of tomorrow’s Monterey pine forest begins the next chapter in nature’s cyclical story.

The Monterey pine, or Pinus radiata, is a species whose story is richly interwoven not only with the living legacy of Cypress Lawn but also across the broader central coast of California to which it is native. This remarkable tree is one of a triad known as the California closed-cone pines, along with its sister species the knobcone pine (P. attenuata) and the bishop pine (P. muricata). Each of these has a fragmented native range of “arboreal islands” scattered across the California coast region, remnants of a far more continuous coastal distribution of pine forest in the cooler, moister geologic past.

Today, insular pockets of Pinus radiata may be found at Point Año Nuevo, with larger forest stands on the Monterey peninsula, as well as near San Luis Obispo, and then as far south as Cedros Island offshore of Baja California. These few “arboreal islands” are but whispers of a bygone glory, of vast stretches of an archetypal Californian flora. What remains — as too with the memories of people we love — we must cherish!

All of the closed-cone pines, including our Tree of the Month, have evolved a radical way of living — and of passing life to the next generation of forest — that harmonizes with the natural processes of the California landscape. Throughout our state, as has been made very evident in recent autumns, seasonal wildfire is a prevalent characteristic of the annual cycle of life and climate. The natural drought summers of California characterize a Mediterranean climate, and this native pattern of our environment sets the stage for a drying of vegetation across the landscape, then ripe for ignition and spreading fire in the fall months. Just as indigenous people in California lived in concert with nature for thousands of years, Pinus radiata knows of a way to embrace the flames as a gift and yield purpose from such warmth. The Monterey pine and its related kin have adapted a specialized means to not only survive the inevitable fires but to thrive as a species precisely because of them.

Shown here in detail are examples of both a closed (left) and open (right) Monterey pine cone. These serotinous cones have nearly a hundred scales, each of which is sealed by a special resin. When a critical temperature around 120 degrees Fahrenheit is reached, this resin will melt, and with a loud pop, the cone scale will open, releasing its winged seed in time.

When walking across Cypress Lawn on a hot, arid summer day, listen carefully. You may just hear an occasional “pop, pop, pop” — quite like the sound of popcorn at a movie concession stand. The theater of life, however, is a show unlike any Hollywood picture, a spectacle that has been decades in the making. The “pop, pop, pop” you are lucky to hear is the sound of Monterey pinecones opening in the heat, the resin of each cone scale melting in the summer swelter.

Each of the many seeds held within a singular Monterey pine cone is equipped with a specially adapted wing, which carries the seed gracefully down to earth to find its growing place. The seed’s fall is stabilized by this single wing, which rotates around the seed’s weight, like a lone helicopter blade, throughout the windy descent.

Either by extreme heat, or through — you guessed it, fire ‑ the seed-bearing female cones of Pinus radiata will open. And so, their seed might ride the wind, helicoptering through the air like a spinning top, to land and, with any luck, germinate on a nearby slope. This life history trait is known as serotiny — the condition of bearing serotinous cones.

In a state where, throughout geologic history and still today, fire lives as an integral process of the landscape, the closed-cone pines embrace nature’s way. As fire-obligate seeders, this triad of pine species are largely dependent upon a high-mortality fire event to reproduce, casting their multitude of offspring upon the land to rise in the wake of their mother’s ashes. As the phoenix, emergent in the spring sun, the next generation of Monterey pines will grow to yield tomorrow’s forests — and so the pages of life turn to the next chapter.

The moment of life turning the page, transforming from one generation to the next, is encapsulated (literally!) within a Monterey pine cone. An apt metaphor, certainly, for what we care for most here at Cypress Lawn — the celebration of life!

The persevering pines offer what I see as a seed of hope, a glimmer of possibility, in the context of what most of us would regard as utter calamity. The nature of these wooden beings is one of fortitude, of ingenious resolve through crisis, of harnessing the opportunity that is at the root of every disruptive transformation. “Necessity is the mother of invention,” and the serotinous seed is the daughter of fire.  In these traumatic days, might we not channel the message, the way of the closed-cone pines, and open ourselves to a new path for partaking in and celebrating life, even as the tragedy surrounds us? I say, heed the wisdom of the trees, find courage in the meaning they bestow, and strive forward with innovative purpose!

This colossal trunk is a distinctive feature of the Monterey pine’s form and function. The deeply fissured bark is made up of dozens of individual layers, stacked upon one another as the “skin” of the tree grows thicker each year. The actively dividing cells on the inner side of the pine’s bark comprise the cambium — this actively dividing and differentiating layer of cells grows both inwards and outwards (producing xylem and phloem, respectively) as the mature tree thickens over the years.

In kind with the Monterey pine’s way of living, adapted to regeneration by fire, the species is a vigorous and rapid grower capable of reaching cone-bearing maturity in two decades or less. Typically, Pinus radiata has a relatively slight overall lifespan of little more than a century. For this reason, many of the mature pines planted in the early days of Cypress Lawn are beginning to senesce, or naturally decline and wither as their end draws near.  These senescent trees may become an overhead hazard to Arboretum visitors, and so in recent months, we have initiated a tree removal campaign to allow everyone to continue to enjoy walking the grounds, with safety for all as a top priority.

Death, for trees and for you and me, is the final chapter in our earthly stories. Here at Cypress Lawn, to honor the dead is to celebrate the life shared, and the Monterey pine is a poignant example of this lasting legacy. Just as the next generation of the Pinus radiata forest emerges from the ashen remains of their ancestral woods, so too will the fallen pines of Cypress Lawn past give rise to the Arboretum of our future.

In collaboration with Davey Tree and other contracted arborist groups, the Cypress Lawn Arboretum has begun an initiative to remove any senescent, or decaying, Monterey pines on our grounds. The species is not very long-lived for a tree, and so this project will be implemented to keep Cypress Lawn safe for all future visitors. Thankfully, after the trees have been felled, all of the remaining wood may be put to new purpose.

How could this be, you might ask, given that fire has no place in the landscape’s process here in Colma now? Well, instead of being reduced to ashes, each of our senescent pines is transformed into a heaping mound of … mulch! By passing through a standard chipper, the majority of woody biomass that was a dying Monterey pine yesterday is given new purpose today as a vast supply of greenwood mulch. This sustainable plant material, when applied properly, is vital for nurturing the sensitive early days of the many dozens of newly planted seedlings, or young trees, throughout the Cypress Lawn Arboretum. A layer of pine wood chips a few inches thick, circling a ring around a tree’s trunk — but never directly on the trunk — affords a multifaceted benefit to the youngest individuals of our living collection.

A seemingly endless supply of mulch is now being utilized throughout the grounds of our Arboretum, helping to support and nourish the dozens of young trees planted just this year here at Cypress Lawn.

Oh, the many advantages of mulch! Truly, any tree is better off with a healthy layer of mulch, properly installed and maintained. A quality mulch ring is 3 or 4 inches thick, with greenwood pine chips as one of the finest materials that can be used. Remember: A mulch ring should never come right up against the tree trunk itself — “It’s a bagel, not a bun!”

A primary advantage of implementing mulch rings is to improve soil moisture retention, as the earth surface in the root zone is protected from direct exposure to the heat of the sun. Soil nutrient cycling is also aided by the presence of a healthy mulch layer, including from a tree’s own leaf litter decomposing in situ over time. Soil microorganisms and beneficial fungi thrive in mulch and increase the young tree’s vitality. Furthermore, mulch can help to suppress the early growth of weeds within the dripline — the outer circumference of the tree’s canopy — and will reduce the potential of climbing vines such as Algerian ivy (Hedera canariensis) from beginning to use the tree architecture as a living scaffold. Simply put, mulch is magic!

There are many values in using greenwood chips — especially of the high quality offered by our deceased friends the Monterey pines — to implement mulch rings throughout our living collection. And so, in passing, these fallen giants will steward forth the next generation of trees here at Cypress Lawn, for these to thrive and grow in kind. Onward, in concert with the processes of nature, so we go. The circle of life rolls on, indeed!

Perhaps the lesson offered by the life of the Monterey pine is this — each of our personal stories is finite, and we know not what the final pages of our own shall read. But the beauty of message, of meaning, is that each telling of the tale brings an opportunity to share knowledge and celebrate the wisdom of the past, with lessons learned anew. Just as we treasure the memories of our own families and ancestry, rekindling bygone stories of nature’s way can be a gift that gives and gives. The spreading of pine chips in the shade of a vigorous seedling is — dare I say it — a metaphor for the passing of knowledge from our ancestry to our future. Live and learn, so they say, and why not teach as well?

Together, as we continue to persevere against all manners of adversity, our collective resilience will find a way forward, as too does the Monterey pine.

We here at Cypress Lawn stand with you, trees and people alike, proud to continue to serve families, find the good, and to celebrate life!

With a mature and thriving Monterey pine off in the distance next to the obelisk of the historic Laurel Mound, two hawthorn trees showcase their newly installed Monterey pine greenwood chip mulch rings. With rings like these in place for young, establishing trees throughout our grounds, the future of the Cypress Lawn Arboretum may grow strong and tall into the next generation of our living collection.