Management and Treatments

Setting the Stage

Establishing the Buxton Pollinator Meadow is a one-of-a-kind project that is still in its early stages.  In much of the meadow area, the existing vegetation lacks the diversity and cover of nectar- and pollen-producing herbs necessary to boost local pollinator populations. Our primary goal is to form plant communities dominated by native bunchgrasses and a profusion of wildflowers that bloom throughout the entire Pacific Northwest growing season, from February through October.

Complex challenges ranging from a dense cover of exotic, aggressive grasses to underlying soils that store a great abundance of weed seeds have required our Horticulture team to develop and experiment with a range of management approaches and treatments. In addition to our ambitious ecological and aesthetic goals, we aim to share the knowledge we gain as we learn about the efficacy of various treatments, and how we can improve treatment outcomes. Our visitors will see these methods in use throughout the meadow at different locations and in different seasons and years.

If your curiosity is piqued and you’d like to learn more, please explore the text and accompanying pictures by topic below.

Fundamentals of Meadow Ecology in the Pacific Northwest

The following is a review of the basics of meadow ecology and management, intended to provide additional context for our experimental treatments. Meadows are complex ecosystems that exhibit enormous inter-annual variability, and it can be difficult to assign cause and effect to an observed pattern. For example, a change in cover of a particular species or group of species from one year to the next may be a result of intentional management interventions, or it could be a result of weather, competition, or predation, or a combination thereof. However, a handful of fundamental strategies rooted in meadow ecology are practiced universally.

Preventing Woody Encroachment

The most important practice is the annual removal of encroaching woody plants mechanically or with fire. As in the Buxton Meadow, open spaces dominated by herbaceous vegetation are often surrounded by woodland or shrubland, and the trees and shrubs in these adjacent areas spread their seed into open meadows via cones, catkins and fruits. In a process called succession, the seeds grow into mature shrubs and trees, which out-compete grasses and herbs, eventually forming closed canopies that shade the ground and make the site impossible for low-growing, sun-loving meadow species to survive on. Consequently, if woody shrubs and trees aren’t regularly eradicated, meadows will not remain meadows and will convert to shrublands or woodlands instead.

The Role of Grasses

While a pollinator meadow may be mostly prized for its wildflowers, grasses are an integral component of meadow ecosystems. Grasses fill an ecological niche, or a range of conditions and resources within an environment. On a site dominated by herbaceous vegetation, grasses will be present because their propagules are ubiquitous and their extensive root systems occupy the soil profile in ways that the roots of flowering herbs do not. In other words, flowering herbs (forbs) and grasses occupy different niches. The spreading, deep, fibrous roots of grass plants cause ecologists to classify them as the fabric, or underlying weave, of meadow ecosystems. It’s vital that the managed meadow support desirable, native grasses, otherwise aggressive and problematic grasses are certain to establish and fill the empty niche instead. Although it is true that over time, grasses will out-compete forbs and periodically need to be removed to make room for valuable pollinator plants, this process is much less of an issue for meadows dominated by native bunchgrasses than it is for those dominated by rhizomatous or mat-forming Eurasian pasture grasses (as is currently the case in our meadow).

Conditions for Successful Seeding

Other foundational principles of meadow management relate to seeds, including seed sowing and how seeds are stored in soils. Perennial seeds are typically sown in the fall because they require prolonged exposure to cold, wet conditions in order to germinate. However, this process of “stratification” can be mimicked artificially by mixing seeds with moist sand or other inert, granular material and storing them in a refrigerator for one to three months, depending on the species. Seeds of annuals (plants that complete their life cycle in one year) will germinate readily without stratification and are sown in spring. Whether sowing perennial or annual seed, the site should first be thoroughly cleared of vegetation, because direct contact with mineral soil is necessary for the germination of both. This includes the removal of thatch, or dead plant material, which can be a significant barrier between seeds and soils; absent any interventions, as thatch builds up over the seasons, annual plants will begin to disappear as the bare soil they need to continue self-seeding becomes scarcer.

Annual herbs may disappear over time, but perennial seeds, particularly those of weedy, undesirable species, can build up and persist for long periods in the soil in a process known as seed banking. These seeds linger until the soil is disturbed and they become exposed to light, causing them to germinate and reappear from areas where live plants were previously absent. This phenomenon means that a site may appear to be weed-free because there aren’t any living weeds, but the weeds are still present in the form of seeds, ready to vigorously reestablish given the opportunity. Weedy seed banks present significant challenges to meadow conversion projects like ours.

Climate Considerations

A final piece of relevant meadow ecology is the relationship between season and plant growth. Our region has a Mediterranean climate characterized by mild, wet winters and hot summers that receive very little precipitation. These conditions favor herbs that actively grow in spring and fall when temperatures are moderate and soils hold adequate moisture, and that enter dormancy in the summer when there is very low water availability. Plants that follow this growth pattern are known as cool-season plants. In contrast, warm-season plants are herbs that originate from regions like the North American Midwest, where summers are both warm and wet. These plants don’t start growing until temperatures are higher and in our region, they require summer irrigation because it seldom rains when they are actively growing. These differing growth patterns have implications for species selection and irrigation practices. For example, bee balms (Monarda spp) and coneflowers (Echinacea spp.) are highly valuable pollinator plants, but they are warm-season species that arose in the Midwest where summer precipitation is significant and consequently, both require summer watering to survive in our region.