At the Minnesota Landscape Arboretum, Mary H. Meyer and Nick Kreevich explore the human side of hedges.
Believe it or not, a hedge collection can be full of surprises. Take the row of 20-25 foot-tall Jack pines, Pinus banksiana, just one of the 73 taxa in the Hedge Collection at the Minnesota Landscape Arboretum (MLA). These tough natives have great cold and drought tolerance—but what are they doing, unpruned, in this formal hedge collection? The historical documentation of the collection provided crucial clues: From early curatorial records, we learned the Jack pine hedge was made up of plants grown from seed collected by Al Johnson, an early MLA curator, from a witch’s broom in Chittamo, Wisconsin. In slides, we found pictures of plant people with witch’s brooms, from which they coveted seed in hopes of finding new dwarf plants. While the story of the Jack pines is clearer now, broad questions remain: What did record-keeping look like in 1967? Whose idea was it to start the collection? Was there an initial donor or collection goal?
These were some of our questions when we began to write our new ebook, Hedges: A Brief History and the Minnesota Hedges Collection, and document the institutional knowledge of the collection. Although each plant had its own record with basic provenance information, our questions were not easy to answer. When we tell people (even horticulturists) that we wrote a book about hedges, they often look puzzled; when we ask if they grew up with a hedge, or if they ever pruned a hedge, however, most often the answer is yes. We ask them to think about why the hedge was there, and what it might have meant to their family and neighbors. And for many people, a light comes on as they connect their hedge to the landscape and its cultural meaning.
Established in 1958, the MLA began as a horticultural research site for testing winter hardiness of plants (USDA hardiness zone 4), including plants commonly used in hedges. The MLA Hedge Collection is one of the oldest such assemblages, due in part to the boom in popularity that hedges saw throughout the 1960s, thanks to the postwar building boom and the growth of suburbia. Sifting through thousands of more-than-60-year-old, 3 × 5-inch accession cards, filed in Steelmaster card cabinets, is like discovering an old journal or generational photo album at a yard sale: as soon as you start moving your fingers across the edges of the cards, musty whiffs of past time bring on a feeling of nostalgia. With each flip of a card, organized alphabetically by generic, specific, and cultivar epithets, you begin to build a historical portrait of the MLA collections dating from 1958. These index cards, also known as accession records, reveal that acquiring a plant and giving it a number did not necessarily coincide with when it was planted. Documentation on the cards also includes notes on fall color, winter injuries, fruit set, and overall growth habit—all important considerations when assessing the ornamental value of a hedge. It is clear from the records that prior keepers prized foliage density, foliage color, and winter hardiness above all. We could even trace the impacts of weather on the hedge collection, with two of the coldest winters in recorded history (1978-9, with an average temperature of 9.4°F, and ’77-8, with an average temperature of 10.5°F) apparent in plant-record notes on injury and severe dieback. Natural selection certainly took its course with those back-to-back weather events, but also provided the staff with critical knowledge of how particular hedge plants respond to extreme cold.
For many people, a light comes on as they connect their hedge to the cultural landscape.
We also interviewed a number of employees, current and retired, to record their memories and discover the origins of some of the more unusual plants in the collection. Kathy Allen, Andersen Horticultural Librarian, assisted with locating the early Arboretum annual reports, which add critical details regarding scope of and sup- port for the collection. “The collection was planted to show which plants were the best for formal hedges,” recounts Director, Peter Moe, himself a longtime MLA employee. “There were fewer compact forms of many species at that time and many people tended to try to keep large plants such as Amur maple as medium-sized hedges.” Height, density, and diversity could be shown in a planting a variety of hedges, which at the time were an extremely common and desirable landscape element.
Three taxa of boxwood (Buxus ‘Glencoe’ Chicagoland Green™; B. microphylla var. koreana, and B. sempervirens) are the only broadleaved evergreens in the collection. Notes from early Arboretum newsletters express interest in this genus, though it was thought not to be winter hardy by many. Accession records and notes from the ‘60s to ‘70s document the overturning of this wisdom, with comments such as “best in collection” and “very good hedge material.” Although the plants show winter burn in the spring many years, the hardiness of boxwood hedges is no longer a question.
Guided by prior documentation standards at the MLA, evaluating our current hedge collection for ornamental value sometimes felt like being a judge for the Westminster Kennel Club Dog Show, looking at one favorite after another. Usually, the first concern when pondering a hedge is its performance as a barrier. Yet not all hedges intend to create a barrier, but may instead provide ornamental value to an existing landscape or garden. The latter is mostly a matter of opinion: some may be wowed by the texture or height of a hedge, while others are more interested in the seasonal changes such as flower, fruit, and fall color.
Our Thuja occidentalis ‘Wareana’ (American arborvitae) was the clear winner in terms of privacy, reaching heights of up to ten feet at maturity, with very dense, evergreen foliage. On the opposite end of the density spectrum, a hedge like Hydrangea arborescens ‘Annabelle’ (smooth Hydrangea) needs consistent renewal pruning to provide what it is best known for: its large, rounded flower heads. While the ‘Annabelle’ hedge can reach heights that garner it semi-private status, there is no hiding behind this deciduous shrub come winter. Deciduous hedges vary greatly as the seasons change, and will react strongly to weather anomalies. Early in the growing season, Philadelphus coronarius ‘Aureus’ looks like a candidate for removal, but its charm and value for use in a hedge come to fruition in the summer, with its beautiful chartreuse foliage.
Our reaction to plants is often subconscious; we rarely realize how deeply they affect us.
Such factors are boldly visible through the seasons at the MLA, when you drive over the crest of a small hill and 73 neat hedges suddenly spread before you. It is hard to not notice them! Our hedge collection is a document of human intervention in the landscape. While it is doubtful that we would plant a hedge collection in a public garden today, there is value in keeping historical horticultural garden elements intact for future study. This preservation effort encompasses both plants and the records we keep of them.
And so a word of advice to anyone thinking of fleshing out historical documentation for a plant collection: much institutional knowledge exists only in the memory of long term staff. Documenting this tacit knowledge, with audio or video recordings if possible, as well as continuing to keep records beyond mere accession numbers, will help curators, horticulturists, and other Arboretum staff understand the goal and educational purpose of a collection. Rarely do we over-document the details of our plant collections. As authors on hedges, our perspective has become more complex, realizing that people subconsciously use hedges to take control of their property and show authority. Some may balk at using the word “authority” in connection with a hedge. Our reaction to plants is often subconscious, however; we rarely realize how deeply they affect us. A well-pruned hedge subconsciously communicates human control, and implies a safe, managed landscape. Our species’ role in the landscape is readily seen, but often not fully recognized, when we encounter a hedge.
Mary H. Meyer, Professor emerita at the University of Minnesota, has worked at the Minnesota Landscape Arboretum for 35 years, currently serving as Curator of the Grass Collection. Nick Kreevich is Cartographer and Plant Recorder at the Minnesota Landscape Arboretum.
From “free” to “friend”…
Established in 1911 as the Bulletin of Popular Information, Arnoldia has long been a definitive forum for conversations about temperate woody plants and their landscapes. In 2022, we rolled out a new vision for the magazine as a vigorous forum for tales of plant exploration, behind-the-scenes glimpses of botanical research, and deep dives into the history of gardens, landscapes, and science. The new Arnoldia includes poetry, visual art, and literary essays, following the human imagination wherever it entangles with trees.
It takes resources to gather and nurture these new voices, and we depend on the support of our member-subscribers to make it possible. But membership means more: by becoming a member of the Arnold Arboretum, you help to keep our collection vibrant and our research and educational mission active. Through the pages of Arnoldia, you can take part in the life of this free-to-all landscape whether you live next door or an ocean away.