11 minute read
Aligning With Nature: The Many Reasons To Grow Native Plants
By Denise Knapp, Ph.D., Director of Conservation and Research
The native plant revolution is growing, and it seems that more and more people are realizing native plants provide vital habitat. While this is my favorite reason to grow native plants, there are a number of other important rationales which are not typically recognized. In this article, I’ll explore them — from the benefits of biodiversity and beauty to heritage and habitat. And, perhaps most importantly, I’ll explain the ability of native plants to tackle the dual threats of biodiversity loss and climate change.
These concepts aren’t new. Indigenous farmers have always operated in such ways. Techniques spread northward from Mesoamerica and became widespread throughout North America, with Indigenous farmers perfecting cultivars for their region over many generations. This regional crop diversity unfortunately began to diminish when early European settlers forced Native people out of their ancestral lands. That was the start of a terrible trend, but we can reverse it. Let’s look at the Three Sisters, for example. Many Native American tribes plant corn, beans, and squash (aka the Three Sisters) together because they each bring something novel to the group and nurture one another. First, corn is planted, and as the seedlings grow, the soil is shaped to form small mounds. Then, beans are planted on those mounds, with the cornstalks providing “poles” for the beans to climb upon and the beans bringing nitrogen to the soil. Lastly, squash or pumpkins are planted between the rows; their large leaves shade the ground, which both holds in moisture and inhibits weed growth. Together, these “sisters” provide complementary nutrients and sustain life for the humans who grow them. To me, this Three Sisters method and story perfectly conveys the importance of biological diversity and respect for the natural world, of which native plants are the foundation. Each species has a niche to fill and a role to play, and together, they provide the things we as humans need for body and soul: food, yes, but also clean air and water, shelter, medicine, nutrients, and soil stability, not to mention beauty and meaning.
California’s Abundant Natural Beauty
Here in California, we are one of 36 globally recognized hot spots for biological diversity. Nearly one-third of the world’s flora is found only here! With so much native beauty all around, where do we start?
One of my favorites are elegant, red-barked manzanitas (Arctostaphylos spp.), of which we have almost 60 different kinds. These “little apples” (the Spanish origin of the name) have adapted over millennia to the different climate, soils, and creatures found throughout the state. In my hometown of Lompoc alone, there are two endemic manzanitas that thrive in the fog, wind, and sandy soils of the Burton Mesa. Similarly, two endemic lilacs (Ceanothus spp.) grace the hills there with their sprays of blue flowers in early spring. In the bare sandy openings in between these shrubs, you might come across the rare annual Vandenberg monkeyflower (Diplacus vandenbergensis), with happy lemon-yellow flowers that dwarf their little leaves. Or you might see the floriferous endemic wallflower (Erysimumcapitatum var. lompocense) with petals like tangerine honey. Maybe you’ll catch the intoxicating sweet mint smell of curlyleaf monardella (Monardella undulata) before you see their royal purple flowers, but you’ll fall in love either way. Both on their own and together, these plants are sensational. This bounty of beauty is just one of the reasons to conserve and restore our native flora.
California’s Landscapes Give Us a Sense of Place
California’s botanical diversity is also our heritage, which is reflected in place names throughout the state — particularly for plants that provide food, water, and shade. According to Erwin G. Gudde’s book “California Place Names: The Origin and Etymology of Current Geographical Names,” more than 50 locations are named for the native wild strawberry (Fragaria chiloensis spp.), one of two ancestors of our modern food plant. A favorite food of original Californians, the hollyleaf cherry (Prunus ilicifolia), is called “islay,” which is a name that also appears in several San Luis Obispo County locations. And because their presence usually means that there is water present, cottonwoods (Populus spp.), willows (Salix spp.), and sycamores (Platanus spp.) are California place name favorites. What’s almost as important as food and water? Shade and firewood to regulate our temperature. So, it’s no surprise that “pine” (or the Spanish equivalent, “pinos”) and “oak” (Spanish equivalent, “encino” or “roble”) are some of the most popular place names in the state. For example, Encino and Encinitas are named for the evergreen coast live oak (Quercus agrifolia), while Paso Robles is named for deciduous types like blue oak (Q. douglasii) and valley oak (Q. lobata). And what’s even better than food, water, and shade? All three at once! The California fan palm (Washingtonia filifera) has inspired many names and was so important to early settlers that the number of trees often became a part of the name (e.g., Lone Palm, Dos Palmas, Twentynine Palms, Thousand Palms, and more).
California’s Flora Sustains Life, Including Our Own
Because native plants have evolved with the creatures around them, they are better able to provide habitat and support entire food webs. Plant-eating insects (herbivores), for instance, can typically only eat a small group of related native plants — so it takes a lot of different plants to support a lot of different insects. Research by Doug Tallamy, Ph.D., from the University of Delaware has shown that native woody plants used as ornamentals support 14-fold more caterpillars (butterfly and moth larvae) than nonnatives! Even for pollinators, which aren’t as tightly tied to their host plants, many species are specialists whose life cycles are centered around the flowering of specific groups of species. In the lab of Gordon Frankie, Ph.D., from University of California, Berkeley, native plants were found to be four times more likely than nonnative plants to attract native bees. Furthermore, other research shows that the web of interactions between nonnative plants and insect visitors is much less connected, making those systems more vulnerable to collapse.
If you zoom out to look at all of these connections between native herbivores and pollinators, you see how they, in turn, support rich layers of parasites and predators. Together, these insects feed reptiles and amphibians, birds, and small mammals, which then feed larger organisms like foxes, mountain lions, and on up the food chain. Again, Tallamy’s lab illustrates this point by finding that bird species of regional conservation concern were eight times more abundant and significantly more diverse on native properties, and even a small proportion of nonnative plants reduced the breeding success and population growth of the Carolina chickadee (Poecile carolinensis). There’s proof all around us that ultimately indicates the value of California’s native plants.
California’s Natural Benefits Make Us Resilient
It gets even better. Not only do native plants support more life, but they can also mitigate the top three threats to biological diversity: development, climate change, and nonnative invasive species.
Development not only has direct impacts to biological diversity but also indirect impacts via the fragmentation of remaining habitat. When large areas of natural habitat are reduced to smaller patches, those areas may be too small to support the same number of species and are more susceptible to nonnative invasion. This fragmentation also hinders the necessary dispersal of both plants and animals. Planting native species where we live, work, and play is one of the best ways that we can soften the impacts of development. Research shows if we converted 15% of our urban spaces to favorable habitats, it would provide plants and animals with suitable living areas and even help them migrate in response to climate change. However, with our urban spaces covered with more and more hardscapes, we need our open spaces to work harder in support of biodiversity. With this in mind, the Garden aims to achieve 30% native plant coverage across the central coast.
Planting natives helps to both avoid the worst climate changes and to adapt to changes that are already in motion. Restoration of diverse habitat and reforestation are important natural climate solutions which cumulatively can compensate for more than 20% of greenhouse gas emissions in the United States. The benefits are especially significant when replacing lawn grasses, which demand high water and chemical inputs (not to mention the fossil fuel use and emissions involved in mowing those lawns). California is already experiencing increased drought, so the fact that native plants typically require less water than nonnatives is key. The facts are there: Retaining and supporting California’s biological diversity will provide resilience to all of the climate change effects that we are experiencing, including increases in extreme drought, heat, flooding, and frequency of fire.
Choose Native Plants and Stop Invasives
Invasive species play a key role in 60% of plant and animal extinctions globally, and their global cost is estimated at $423 billion annually, or nearly 5% of the world’s economy. While some nonnative plant seeds are spread unwittingly through boots, bags, and boat ballast, many others are spread very intentionally — when we buy and plant them. Plants from similar climate regions like South Africa and Australia can look so exotic and exciting, and do well in our gardens, but they have also been brought here without their natural pests. With nothing to keep them in check, the invasive bullies can (and do) run amok. When you grow a native plant, you know you’re not planting California’s next invasive species.
Are You Ready To Grow?
Today, one in eight of the world’s species (and 40% of the world’s plant species) are at risk of extinction. While this is startling, we can reverse this reality by conserving and cultivating native plants and habitats. You can always think of the Three Sisters, growing and supporting one another. We can do the same, as individuals and a community. By conserving California’s diverse plant species in the wild and nurturing them in our built spaces, we can ensure that our ecosystems are resilient to change, and that nature continues to keep us and other creatures healthy and happy.
