Protecting mycorrhizae to promote perennials

By Lauren LewisIMG_9047

In California, where pretty much all gardening is done with water requirements front of mind, the wise approach is to aim for a garden that is dominated by perennial plants- those that live and thrive for many years, rather than a single season or year. (A lot of edibles would be the exception to this trend, but we’ll set those aside.) The reason is that perennials typically need less water as they grow and get established; their roots grow deep and wide and can reach more underground water than those of a very young perennial or an annual. In essence, our gardens aim to mimic a late successional plant community, and to do that successfully, we have to think about the soil.

Ecosystem succession is the process by which an ecosystem changes, after a disturbance, from being dominated by fast-growing, prolifically-reproducing species (among plants this means weeds) to being dominated by longer-lived species that use reproductive strategies of quality over quantity. And the soil — specifically the mycorrhizal fungi in soil that forms a symbiotic relationship with plant roots — supports this process. Recent research has shown that late successional prairie plants (i.e. perennials), grow better in more fungal soil, and also that presence of mycorrhizal fungi in the soil can suppress weed growth. In other words, mycorrhizae have the potential to accelerate the shift toward a perennial plant community in two ways: by suppressing annuals and by promoting perennials.

What this means in the garden is: protect and promote the mycorrhizae. A common approach when creating a new garden is to test the soil for nutrients, salt, minerals, etc, and then amend the soil to fix whatever problems are identified. But this approach can actually wreak havoc on the mycorrhizae and the soil structure. So instead, more-or-less accept your soil for what it is, and choose your plants based on your soil. If you plant perennials that you think have the best chance of thriving in your particular soil and location, the presence of the mycorrhizae will further support those plants.

A celebration of the color brown

By Lauren Lewis

IMG_9063At Small Spot Gardens we are working to eliminate the need for ongoing irrigation in the gardens we design. In California. Where yesterday we had our first little sprinkling of rain in over 6 months. It’s certainly a challenge to create verdant, lush-feeling urban oases when the rainfall is so sparse and sporadic and unpredictable, but it can be done. A lot can be done using desert-adapted plants like succulents of all sizes (there’s a lot to love!), but for the diversity and textures and density we aim for, we’re taking another approach too: embracing the dry, the brown, the unsung sculptural elements of the garden.

The seasons are a little harder to notice in California than elsewhere, but we do have them, and that gives our gardens the potential for interesting variability over the course of a year. Rather than using irrigation to create consistency, we argue that visual variation is an asset and to maximize it we have to incorporate and embrace a wide color palette; one that goes well beyond green and into shades of brown. Brown is often the visual cue for what should be trimmed and removed from the garden, but especially in our climate we can boost the visual interest of our gardens by using the shades of brown that plants give us, rather than shying away from them.

We draw some inspiration for this approach from the New Perennialist movement, made most famous by Piet Oudolf. This gardening movement has been around a long time, but gained wider recognition from its use in New York’s High Line Park and Chicago’s Lurie Garden. The look is characterized most often by closely-packed swaths of perennials and grasses that create an effortless prairie vibe. At Small Spot Gardens we are big fans of dense plantings as opposed to plants spread out in a sea of mulch, as well as the interesting colors and textures that you get from grasses and prairie flowers. You can achieve a lush, soft feel in a mainly brown palette using this approach.

So this month on Instagram we’re doing our part to give brown and other underappreciated garden colors their moment in the spotlight. In our gardens we’re finding the plants that are visually interesting at various moments in the year, and we’re aiming to do that with boldness and confidence. A left-over unpruned flower is one thing, but a whole shrub of purposefully retained browned leaves makes a statement.


Using native Californian land management in current California

By Lauren Lewis

Last year I wrote a post describing the work of M. Kat Anderson, who has delved deep into the ways that native Californians managed the land for their survival, and I suggested that the land management practices of native Californian tribes should be used to address contemporary problems. So now I want to look at whether that’s actually happening, and how. In what ways is modern California using or relearning native land management techniques?

The main issue that comes to mind is fire. Due to decreased precipitation and hotter weather, wildfire season in California has essentially lengthened to be year-round as opposed to concentrated in the summer and early fall. And the fires are bigger, and therefore more destructive, and likely to stay that way as the climate changes and as more people move into fire-prone regions (almost all fires in California are started by human activity). But before the Spanish settled in California, fire was arguably the most important land management practice used by native people. They used regular burns to increase soil fertility, maintain grassland for the plant and animal life it supported, promote growth of important basketry plants along riparian corridors, deter pests, and more. Can we use fire now, like native Californians did, to protect against the highly destructive fires we’re battling?

The idea of using prescribed burns to prepare the land for wildfires is indeed gaining traction, but slowly. Ecologists have begun doing prescribed burns on land preserves, such as the Pepperwood Preserve in Sonoma County, a nonprofit which uses a Native Advisory Council to bring native land management techniques into their natural land protection work. Recent research has shown that using prescribed burns can decrease the destructiveness of wildfires and also may decrease the toxicity of the smoke from wildfires. But the practice faces significant hurdles: forests often need underbrush management first to prevent burns from getting too hot, conditions have to be just right for safety, and wildlands are more and more populated by people who could be put in harm’s way.

As for other kinds of native land management, of which there were many, those techniques have been made unnecessary from a survival perspective by modern farming and manufacturing, but they still hold great value from the perspectives of cultural heritage and species preservation. The reemergence of these plant-focused techniques could be an antidote to the problems of nature deficit disorder and insufficient community connection. The Amah Mutsun Relearning Program at the UC Santa Cruz Arboretum and Botanic Garden is working to build traditional ecological knowledge and test traditional plants and techniques for modern uses. In a much more informal way, we at Small Spot Gardens love to learn about the life-sustaining uses for plants that we now use purely for beauty in the gardens we design. It’s one way we place our gardens in the much greater context of time in the Bay Area.


Versatility and diversity: succulents for the win

By Lauren Lewis

If you’re someone who notices the plants around you (you know it if you are!), you’ve probably noticed that people love their succulents. These fleshy desert plants have become hugely popular for landscaping, indoor plant collections, party favors, etc over the last couple decades. And with good reason because they are hardy plants, drought-tolerant, and visually eclectic and striking. Several interesting adaptations have made succulents a strong candidate for the increasingly-dry California garden.

img_8639.jpgIf you were to describe the look of a succulent, the primary adjective might be something like plump, or fleshy; essentially, full of water. Succulents store water to a much greater extent than other plants because they evolved in dry environments- storing more water when it is available means they can survive through dry periods on the stored water. In addition to storing water they also need to minimize water loss, so they use a form of photosynthesis called CAM (Crassulacean acid metabolism), which is not used by all the flatter-leafed plants.

Here’s how it works: the plant keeps its stomata (holes to the outside) closed during the day to minimize lost water from transpiration, but opens them at night, when it’s cooler. Carbon dioxide is therefore only absorbed at night, through the open stomata, and is converted into a storable form and stored in the vacuoles (the water storage part of a plant cell). Then during the day, when the plant is receiving sunlight, the plant uses the stored CO2 and water to perform photosynthesis. A non-CAM plant could absorb CO2 and perform photosynthesis all at once, during the day, but a CAM plant doesn’t have that luxury due to the high heat outside.

So succulents have evolved extra complicated chemical pathways, as well as various other water-focused adaptations I haven’t mentioned, that make them very useful for gardening in an increasingly hot and dry environment. But that’s not all! They are also especially easy to propagate. When we visit our gardens for routine care, we routinely take cuttings of all sizes from mature succulents, and plant the cuttings right away another place in the garden. The cuttings almost always establish themselves easily, and we’re filling out the garden without buying new plants. If you look around online, succulent propagation guides recommend letting the cuttings (which can be as small as a single leaf) dry out before planting, so they don’t absorb too much water when planted, but we’ve had success both ways.


Trees and carbon intake: the bigger the better

By Lauren Lewis

One of the defining characteristics of trees as compared to other plants is their longevity. Their growth patterns at the cellular level evolved not just for reaching up and out but also for “secondary growth”- the layering, repetitive cell growth that thickens the plant, making it highly stable and durable. This and other longevity adaptations mean trees have much to teach us about the environment of their past, and an important protective role to play as we navigate a changing climate.

Take the bristlecone pine: the oldest non-cloning lifeform on earth. The oldest bristlecones are around 5000 years old, and 3000 years would not be unusual. A big part of this longevity is that bristlecones live in extreme mountain environments where few other plants can live. This means the pines have little competition for resources and also that plant mass that could fuel fires around them is minimal. But bristlecones also have some special adaptations that keep them going. Their wood is high in resin that is an effective deterrent to pests. And they can compartmentalize to minimize damage- when a large root dies, the corresponding section of the tree and it’s bark dies too, which keeps the damage from spreading inside the tree. Eucalyptus does a similar thing, dropping a limb when the tree is stressed, to reduce the resources needed by the tree rather than letting the whole tree struggle.

Tree rings have long been used to understand the age of trees, but they’re now also being used to better understand climate change. After California’s severe drought in 2012-14, some physical geographers used cores of living blue oaks and blue oak stumps to address the question of whether the drought was really very unusual or not. They correlated tree ring thickness with precipitation and temperatures records from the last 100 or so years, and then measured tree rings going back 1200 years to infer the climate in those years. They found that the precipitation wasn’t exceptionally low as compared to previous droughts, but that when you added in the high temperature (and therefore the greater evaporation and overall lower available moisture to the trees), the 2014 drought was indeed exceptionally extreme.

So trees can teach us about ancient climate, and schoolchildren know that Earth’s rainforests act like the planet’s lungs by taking in carbon dioxide and releasing oxygen. But it also turns out that bigger trees are doing relatively more of this crucial work than smaller ones. In a study of over 400 tree species from various latitudes and longitudes, researchers found that as tree size goes up, so does mass growth rate (or rate that the tree builds mass), and therefore carbon accumulation. As an example, in the study’s American old growth forest sites, trees of >100cm diameter “comprised 6% of trees, yet contributed 33% of the annual forest mass growth.” So while it’s great to plant new trees to offset air travel, it’s Earth’s huge, old trees that do more to slow the accumulation of atmospheric carbon. They merit passionate preservation for this and so many other services they provide.


Native bees offer low effort, high payoff species conservation

By Lauren Lewis

You’ve probably seen media about the alarming loss of bees in the last decade or so, and it has most likely been framed as a biodiversity conservation issue. That angle on the issue is misleading because the vast majority of this public attention has been directed, often unknowingly, toward honeybees only. Honeybees are not native to North America and are essentially a domesticated species: highly managed and transported for crop pollination and honey production. The threat to crop pollination from honeybee decline is hugely important — valuable foods like avocados, blueberries, almond all rely on pollination for the fruits to develop — but it’s not exactly a conservation issue with ecosystem preservation as the goal. What does fit into that category is the issue of native bee population decline.

There are around 4,000 species of native bees in the United States, and many of these have shown alarming population decline in recent years. This is a concern if we care purely about the inherent value of biodiversity, but also because native insects are typically linked through their roles as pollinators and prey to so many other species in an ecosystem. (You can’t lose one species in an ecosystem without other species being affected- they’re all connected!) Research has linked native bee population decline to diminished pollen resources following land development, and sadly also to native bees’ higher susceptibility to agricultural chemicals, as compared to honeybees. Some research in California’s Central Coast has shown that honeybees and native bees are directly competing for scarce food resources and native bees may be losing the battle.

The silver lining here is that more research is beginning to show just how important cities can be as refuges for native bees and other pollinators. Studies have shown greater diversity of native bees in cities than surrounding agricultural land, suggesting that the urban environment is more hospitable to the bees. The presence of gardens, which can provide both food (pollen in flowers) and shelter (for native bees that’s most often bare ground or rotting wood for burrowing), is key. Given these relatively minor requirements for survival, supporting native bees is potentially low effort and high impact. City governments could put out PSAs that encourage folks to grow some native flowers, in whatever space they have available, and to leave a bit of bare dirt for bee burrows. (Pointing out that native bees are mostly solitary, rather than swarming, and also far less likely to sting than honeybees, would probably be helpful, too.) Happily, a blooming garden that supports native bees also brings beauty and joy to us humans.


The ecosystem diversity of old SF

By Lauren Lewis and Elisa Baier

Before the SF peninsula was settled by Europeans and urbanized, the landscape of many diverse ecosystems — shrubby, grassy, shore, etc — allowed native coastal Californians to thrive. They lived here without developing any farming methods that we associate with traditional agriculture; instead they carefully tended and collected useful plants, foraged shellfish, and created conditions favorable for hunting. The vast majority of these ecosystems are gone now, but if you know the plants and patterns to look for, you can find each of them in small corners of the city today.


Of all the native plant communities, coastal scrub is the one that modern SF retains the most of, in Glen Canyon, parts of Mount Davidson, and the Presidio. It is categorized by California sage, coyote bush, blackberry, poison oak; shrubby, hardy plants that sheltered small game animals and provided edible berries and a lot of medicinal plant material to native people. A walk through this environment is rich with scents of the leaves’ oils and songs from the chaparral birds.

The Yelamu gained some resources from coastal scrub, but they gained substantially more calories from the large game that grazed on grasslands, so they burned the land regularly to keep it as grassland. (Unburned land eventually became colonized by shrubs rather than grasses, and turned into scrubland.) Because people managed the land this way, native prairie was the dominant plant community when settlers arrived. You can find bits of native grassland on the tops of SF’s hills now, and in the spring when the wildflowers are abundant, you can imagine the beauty of the old expansive flowered grassland with views of the water.

Along the edges of the city were extensive sand dunes, which supported a unique set of super-hardy plants tolerant of salt spray, wind, low-nutrient soil and unstable ground – dune strawberry might be the most recognizable. But because unstable ground is antithetical to development, plants such as ice plant and European beachgrass have been extensively planted for over 100 years to stabilize the dunes, and the vast majority of the habitat has been lost.

IMG_4777A similar explanation applies to the riparian and wetland habitats of old SF. Unsurprisingly because of the presence of water, these habitats were biologically very rich, but bay fill and culverting has resulted in just small remnants. The free flowing portion of Islais Creek in Glen Canyon Park gives a sense of what creek habitats may have been like and Heron’s Head Park resembles the marshy habitat once surrounding the peninsula on the bay’s edge.

We’re lucky that some parts of the natural world will probably be apparent in San Francisco as it grows – the steep hills, ocean and bay will likely be obvious forever. To see the more subtle parts of our natural history we’ll have to conserve what still exists and maybe attempt to reconstruct other areas, like old marshes or creeks. At Small Spot Gardens, we suspect that having access to California landscapes in San Francisco helps us connect to a bigger picture – maybe living with and learning about the old ecosystems and the people who tended them will help us understand how to individually handle an increasingly fast paced world and how to collectively approach a quickly changing climate.