Broadleaf stonecrop -- Sedum spathulifolium

We have just ducked under a fallen giant, the corpse of a massive Douglas-fir recently toppled and resting on a steep hillside. Far downhill, branches of a former canopy touch the river that we have been following. Looking uphill I can see the flared root crown, where trunk once met ground. From this crown, gnarled roots reach back for the hold they were unable to sustain, grasping at straws. This is not an unusual sight and coming up the Duckabush River on the eastern edge of Olympic National Park, we have seen a lot of big trees on the ground. Along this short stretch of trail there are five or six huge trees down, probably all victims of the same wind storm. Among these trees, miles upriver from the trailhead, even further from the shoreline, past the blowdown, we find a campsite. Exploring beyond the campsite, we come to a rock-filled area at the bottom of another steep slope, a place too unsettled for big trees. In this pocket of open land, the rocks are overrun with a plant that I didn’t really expect to see here in the middle of the thick forest, broadleaf stonecrop (Sedum spathulifolium). This is a stonecrop stronghold, a sedum kingdom, a jumbled boulder field with an open window to the blue sky above.

Broadleaf stonecrop are ground-hugging perennials which form thick mats of tangled rhizomes, rooting where possible and forming numerous basal rosettes of succulent leaves. Individually, a plant can spread a foot or two across, but much larger mats comprised of multiple interwoven plants are frequently found. The tightly-packed leaves are evergreen in the sense that they persist throughout the year, but they aren’t ever exactly green. Spring through fall, the leaves are mostly blue-tinged green, or glaucous, thanks in part to a strange white powdery substance that covers them and gives the plant an almost silver cast. During the winter, the older leaves on the periphery of each rosette take on a wine-red coloration, though still softened by the persistent powder. Even in winter, the youngest leaves tightly bound at the very center of each rosette generally retain their summer color. Similar to other types of stonecrop, broadleaf stonecrop leaves also change color in response to sunlight exposure, taking on a red coloration in areas that experience intense sun. From among these ground-hugging sets of leaves, stems up to 7 inches in length begin to rise in early summer. These are the flower stems, the tops of which are crowned with clusters of small but intensely yellow star-shaped flowers. The stems themselves, like the leaves and flowers, are often artistically colored. Sometimes deep red, sometimes puce, and other times an unnatural hot pink, the color of the lower portion of the stem starts to fades about half way up and becomes chartreuse, an unresolved mix to the top, the yellow from the flowers above fighting the natural inclination of plants to be green.

The leaves of broadleaf stonecrop certainly stand out among western Washington plants. There is no mistaking them even when lined up against the other species of stonecrop that grow nearby, none of which are coated with the distinctive white powder. Their shape is also fairly unique. They are thick and fleshy, flattened like a spatula, giving them their species epithet spathulifolium. Having these succulent overlapping tabs for leaves is pure function. Filled with water, they serve as storage tanks that allow broadleaf stonecrop to survive long stretches without rain and offset the exceptionally well-drained soils in the places they prefer to grow. Susceptible to rot in waterlogged soils, they still need water to survive. So like other succulent plants, they pick out dry spots and hold precious water in their leaves.

In Washington, we’re near the northern extent of their range. It is sort of disconcerting to find them here along the Duckabush River because they evoke a much drier and hotter landscape. Perhaps most at home in the climate of northern and central California, broadleaf stonecrop also has scattered populations from southern California up through extreme southwest British Columbia. South of Washington, they can be found out along the exposed outer coast. This far north, where the coastline is battered by storms throughout much of the year, the land is too wet and densely forested for these little sun-lovers. Here, they prefer the calmer and sheltered coastline along the northern end of the Olympic Peninsula and throughout the San Juan Islands. The area is often referred to as the “Banana Belt” because of its relatively dry and sunny climate, a result of sitting in the rain shadow cast by the Olympic Mountains. Most storms here come off of the ocean from the southwest and so the mountains that make up the interior of the peninsula create a physical barrier that stops a lot of this rain from reaching the area directly beyond them. In summer, this small area is warm and dry, in winter it’s mild and fairly dry. It is like a California satellite floating in western Washington space and just the sort of place for the little California plant, broadleaf stonecrop.

With a name like stonecrop you expect to see them growing among rock, and so they do. In boulder fields, rocky shorelines, balds, and cliffs, from crevices or snaking around in the built up organic matter between boulders, broadleaf stonecrop is never far from stone. Taking root where meager soil accumulates in small cracks or is layered thinly over rock, these plants thrive where conditions seem poor. And that is part of what makes them lovely. Growing as often on vertical walls as running horizontally along the top of boulders, broadleaf stonecrop so often combines with moss to soften cold rock and brittle lichen, which in turn give an edge to the plants going on them; each element an excellent foil to the others.

In California, broadleaf stonecrop plays an important role as an essential life partner to a tiny and unassuming endangered butterfly, the San Bruno elfin (Callophrys mossii bayensis). San Bruno elfin mate in early spring and lay their eggs on the leaves of broadleaf stonecrop. The plant then serves the vital role of nourishing the larvae from the time they hatch until they pupate. After feeding on the succulent leaves on which they were born, by late spring these larvae climb up the stem to the clusters of yellow star flowers opening overhead. Here they feed on the flowers themselves until they are fully mature and ready to become butterflies. Once they pupate, San Bruno elfin will not return to broadleaf stonecrop until it is time to lay eggs again. All life needs a safe and reliable nursery and for San Bruno elfin, that nursery is broadleaf stonecrop and nothing else.

Like so many other endangered species, San Bruno elfin exhibit both severe endemism and specialized associations, in other words they are neither widespread nor adaptable. These qualities make them highly susceptible to being squashed by the big clunky foot of human development and its unintended consequences. Complicating matters for this butterfly, its small native range lies exactly where San Francisco happened to pop up. As a result of urbanization, broadleaf stonecrop is much less common on the peninsula than it used to be and what remains is highly fragmented. Broadleaf stonecrop was likely once widespread throughout the San Francisco Bay area and with them, San Bruno elfin were likely more abundant. Today, subpopulations with enough plants to actually sustain San Bruno elfin are mostly found in the few protected wild areas through the city, such as on San Bruno Mountain. Looking at a satellite imagine of the city, it’s hard to imagine the diminutive elfin on San Bruno ever being able to escape its mountain island, so conservation of that remaining wildland is hugely important to the survival of this species.

For people in certain parts of San Francisco, planting broadleaf stonecrop in their gardens could have significant ecological benefits, but all up and down the west coast, they make a great addition to gardens even where they have no specialized ecological associations. They are a popular garden plant not only because they are beautiful, but because like many other types of stonecrop, they take very well to cultivation. Easy to keep alive and fairly quick to spread, they can be a superb groundcover or a foolproof addition to a rock garden, the type of plant that can serve as an anchor and allow a person freedom to experiment with more finicky plants. And like other stonecrop, they would probably also be well suited to a green roof. A love of sun, preference for little water and thin soil, spreading quickly and weighing next to nothing, stonecrop are perfect for a green roof.

Back along the Duckabush River, I’m taking a lot of pictures. I have seen broadleaf stonecrop before down along the shoreline in areas where they can dominate, but it’s really fun to find them in this unexpected place, surrounded by many miles of trees in every direction. Looking at them here, I realize just how incredibly loud these little plants are; their leaves, stems, and flowers taken together, like a neon sign flashing in the window of this somber western Washington evergreen forest. I again say thanks to our colliding tectonic plates for all of this mountain building. They have given this area incredible topography and have created the microclimates in which some interesting plants eke out a life that would not otherwise be possible here in the rainy Pacific Northwest.