How we can connect landscapes on campus and in hearts and minds

The Forest & Garden Continuum

How we can connect landscapes on campus and in hearts and minds.

By Caroline Tait, Vice President, Horticulture & Collections

On walking the grounds at Holden Arboretum one is amazed by the range of plants in the highly designed cultivated gardens. HF&G’s Living Collection is displayed in representation of a green living museum. However, we host and care for many additional plants of native and natural occurrence throughout the Arboretum Core. These are visible in a series of forested areas, which connect the cultivated gardens. In a much broader scale one can recognize this in our residential landscapes, too — gardens connected by wild, often lightly forested, spaces. It became apparent that we have an opportunity to offer HF&G guests a close-up introduction to the options available to manage this type of space. If an interest is piqued, then the Working Woods program can teach larger scale action in woodlands for aesthetic and economic benefits. Ensuring that any program within a department utilizes the best of knowledge from across HF&G teams means our guests receive the best of current management understanding, and our horticulture teams can implement our scientist’s research. Science and Horticulture are points on a continuum of understanding the land.

Public Gardens as Sentinels of Invasive Plants

By Tom Arbour, Curator of Living Collections

I stepped into the role of Curator of Living Collections last September following a career focused on natives, invasives and land management across Ohio, and am excited to curate our Living Collection of more than 20,000 accessioned plants and trees. My key responsibility is to ensure the Living Collection reflects HF&G’s mission to, ultimately, inspire action for healthy communities. As I begin developing collections plans for each of the individual genera — Quercus, Malus, Rhododendron etc., it is critically important that plants chosen for ex-situ conservation, i.e. conserved on campus outside of their native range, stay in our gardens and do not spread into our natural areas or the communities we serve.

HF&G has taken a lead in recognizing invasive plant species across cultivated and natural landscapes. Norway maple, Japanese barberry, winter creeper and Callery pear are among the dozens of plant taxa that have been removed from our Living Collection although it can take longer for the commercial industry to take these steps. In recent years, Horticulture & Collections staff have collaborated with other public gardens to help sound the alarm about plants that are escaping cultivation locally. This network, known as Public Gardens as Sentinels against Invasive Plants, provides both monitoring protocols and an online database for public gardens to submit information about these plants that ‘may “go wild.”

Plants are categorized as‘‘watchlist,’ ‘potentially ‘invasive’ and ‘invasive’ based on a number of criteria, including information collected by Holden’s staff about the number of plants that have escaped cultivation and how far they have spread from the parent plant. The PGSIP guidance will be implemented throughout the Arboretum Core across gardens and connecting forest fragments.

The Holden Arboretum has a wide variety of greenspaces, creating a continuum from highly designed gardens in the core all the way to our conserved natural areas. The areas on opposite sides of the spectrum are managed very differently and by completely different departments, but sometimes our work overlaps: In the natural areas in the core, our horticulture and conservation disciplines collide, allowing the space to act as a bridge between gardens and natural areas.

Core Natural Areas Recent History

By Ann Rzepka, Director of Horticulture

One of the many reasons HF&G is unique is that one membership affords a matrix of high quality natural and cultivated landscape experiences across multiple campuses. These experiences are the product of time, geologic conditions, evolutionary biology and the foresight of our founders to preserve them. They are held to integrity through planned land management conducted by our boots-on-the ground team of conservationists, horticulturists and scientists in their respective departments.

Traditionally, Science & Conservation department efforts at the Arboretum focused on the natural lands that comprise over 3,000 acres of the Arboretum’s property in Lake and Geauga counties. These natural areas preserve the botanical heritage of Northeast Ohio and provide scientists an opportunity to explore and understand the attributes that contribute to the richness and diversity of these high-quality natural areas and, thus, inform management strategies.

The Horticulture & Collections department at the Arboretum has concentrated efforts toward the care and maintenance of an expanding Living Collection, cultivated for conservation, education and the sheer beauty within the 232-acre core of the Arboretum. Contained by the deer fence, the Arboretum Core comprises a gradient of landscapes ranging from highly designed and curated gardens to managed meadows and forest fragments. In 2020, the departments convened to explore how these spaces could be leveraged in support of the HF&G mission. Staff identified the fragmented forests within the core that were highly visible to guests and began to inventory the species diversity within the existing plant communities. A little over 30 acres of fragmented forests were identified in these initial assessments ranging in size from a half acre to 7 acres — now referred to as the Core Natural Areas. This is significant within the context of the greater forested land in Ohio because small, fragmented forests represent over 1 million acres of the forested land within the state of Ohio, and 85% of these forests are privately owned. (USDA, Ohio Forests Resource Bulletin, NRS -118)

Initial plant inventories revealed an array of invasive exotic woody species, including Frangula alnus (glossy buckthorn), Rosa multiflora (multiflora rose) and Ampelopsis glandulosa var. brevipedunculata (porcelain berry). These invasive species quickly alter the area they invade — changing the availability of water, light and nutrients, and forming dense monocultures, which reduce native plant regeneration and diminish habitat quality (Pimentel et al. 2005). These findings were also significant within the broader context of Ohio’s forested land as the state has a higher percentage of plots with one or more invasive plant species (96%) than surrounding states. (Widmann et al. 2014)