A Perennial Border Reborn

In 1991, the Northwest Perennial Alliance (NPA) undertook a seemingly impossible project: design, plant, and maintain a 17,000- square-foot herbaceous perennial border, entirely with a cadre of dedicated volunteers, at a new public garden, the Bellevue Botanical Garden (BBG) in Bellevue, Washington. That they achieved this task with remarkable tenacity, sweat equity, and international renown is a testimony to the depths of passion that gardening can engender.

Fifteen years later, the needs of the entire botanical garden, its visitors, the City of Bellevue, and the NPA itself had evolved and changed. The Border had grown to 33,000 square feet with over 10,000 perennials and was in need of a major renovation to meet the long-range goals of the Bellevue Botanical Garden’s Master Plan, align with NPA’s available resources, and support the City of Bellevue’s Environmental Stewardship Initiative. In 2007, a partnership was formed that included representatives from the NPA, the City of Bellevue Parks Planning and Resource Management divisions, the BBG, and the Bellevue Botanical Garden Society. This team set out to create a plan that would address the needs, both immediate and long-term, of all the partner organizations and their constituents.

The project was daunting. While we recognized the need to revitalize the plant collections, how could we improve a beloved perennial border? What changes would make it more accessible to a wider audience? How could the ongoing care and maintenance of such a large garden be addressed? Of the plants themselves, what criteria could be used to make cuts or additions? These were a few of the dilemmas that faced the planning team as we navigated through the renovation of the NPA Border. A multitude of comments from many different constituents were heard, layered, and prioritized. Ultimately, ten design objectives were identified to guide the renovation. Glenn Withey and Charles Price, who were part of the design team for the original Border, were selected to turn our objectives into a cohesive and inspiring design.

Key Design Objectives

We first established our primary goals for the Border: keep it healthy and beautiful, with year-round interest, and encourage its function as a learning resource for BBG visitors and for the horticulture community at large. From this, we developed more detailed design objectives:

• Improve accessibility to the plants via safe and comfortable paths and/or stairs.
• Encourage observation and enjoyment through additional seating.
• Reduce maintenance for NPA volunteers.
• Eliminate the slippery grass slope between the Main Border and the Shade Border.
• Consider the size and shape of Border beds to better accommodate maintenance activities.
• Explore the use and placement of interpretive tools.
• Integrate the Border with the Great Lawn, and open views to the proposed Wetland and Sun Terrace Gardens to the west.
• Create graceful lawn shaping and edging.
• Consider the view of the Border from the elevation of the proposed Garden Mount.
• Edit the West Border to significantly reduce the maintenance, while continuing to visually integrate it with the Main Border.

The renovation project was divided into two phases. Phase 1 began in October 2008, with the clearing of the Shade Border and the south end of the original Main Border. The first staircase was poured, and the paths were laid. Many plants were installed, but some were lost in one of the most brutal winters in history. Phase 2 began last autumn, when the second staircase was installed, and the paths were extended into the new area. We waited until winter had passed for the final planting, which is just being completed as you read this. Our deadline was carved in stone: the NPA is hosting the Hardy Plant Study Weekend in June 2010, and the renovated Border must be ready for its debut. The garden will be new and fresh for conference attendees to enjoy.

Structure First

The first objective we addressed was improving access for NPA volunteers to get into the beds to plant, weed, and water, with level paths wide enough for a wheelbarrow and visitors to pass each other. When the paths were laid out, they divided the area into twelve clearly defined beds, thereby making drip irrigation easier to install and control. Having defined beds also simplifies the mapping and labeling of plants in the collection.

One of the most vexing problems that confronted NPA volunteers maintaining the Border over the years was the dense clay soil upon which the Border had been established. For this renovation, the soil was well prepared before installing the new hardscape and plantings. To rid the site of invasive weeds, twelve to eighteen inches of existing soil was removed, and a three way soil mix was added. Now the plants will be able to establish their roots in improved soil that provides for ample drainage and deep root growth, with a good compost blanket on top.

Many iterations of pathways were proposed and debated; building economical, easy-to-stroll paths on a steep clay slope had proven to be a challenge. Now, the new gravel paths function well and welcome visitors of all ages and abilities, allowing them to get up close to the plants for study. The packed gravel drains well, provides access for the volunteers, and accommodates the small turf trucks needed to get materials into the garden. They are wide enough to allow for future plant growth; spilling plants and groundcovers have already softened the crisp edges. One path runs nearly the length of the Border, yet rises and drops only a few feet over its run, making it easy for volunteers and disabled visitors alike. Four new teak benches were carefully situated so that visitors can rest and enjoy the Border from different vantage points.

The two new sweeping concrete staircases beckon visitors across the lawn and into the Border. The southern staircase replaces the steep slippery turf slope; a second staircase bisects the Border at its midpoint. In the future, this center staircase will lead visitors through the NPA Border down to the proposed Wetland and Sun Terrace Gardens, making the new west side of the botanical garden more accessible.

Planting and Maintenance

Once the hardscape features were completed, plants became the focus. Designers Withey and Price have capitalized on the opportunity to update the plant collections and to feature plants desirable for Northwest gardens—not because they are rare, but because they are solid performers. The need for less demanding plants, as well as the desire for the Border to look good for visitors year round, was a driving force in plant selection and placement. Withey and Price emphasized foliage plants, since they need less deadheading and just an occasional grooming to look their best. They repeated groups of evergreen shrubs, such as Buxus, Taxus, and Osmanthus, throughout the Border, along with generous drifts of various Cyclamen and Bergenia, to make the garden greener and fuller on gray winter days. The result is more mixed border than pure herbaceous border, with the repetition of foliage plants lending unity and harmony to the whole.

The individual planting beds now commingle plants needing similar care, with winter interest and evergreens together, and herbaceous drifts massed. This planting approach makes cleanup and maintenance quicker. We have agonized at times over plant choices (after all, most of us never met a plant we didn’t really like), but the main criterion was that plants had to be relatively tough. Plants that needed constant staking and coddling were out. Grasses that don’t flop, such as Miscanthus, Molinia, and Schizachyrium, were given priority over those that do. For similar reasons, perennials such as Agastache, Salvia, and Helleborus were used in quantity. Following the City of Bellevue’s Environmental Stewardship Initiative, we eliminated from consideration any plant that seeds invasively or is difficult to eradicate once established.

The garden is awash with color in the peak summer months. The plant palette jumps from bed to bed on each side of the path, enveloping visitors in a slowly changing kaleidoscope of color. The palette ranges from sunny yellows to deep reds and then to cool silvery blues at the north end. If visitors see plant combinations they like, it will be easy for them to both identify the plants and find them in local nurseries. Moreover, these plants should grow well in visitors’ own gardens. Fortunately, we received many generous donations from nurseries and NPA members near and far.

The planting design also had to take into consideration the long-range plans of the botanical garden, which specified visual, as well as physical, connections between the Border and the future Garden Mount, which will be sited just west of the Border. Plantings on the north end were selected to be relatively low, so that visitors on the lawn will be able to look out over the Border to the Garden Mount.

In choosing plants to be retained and reused from the original Border, we reluctantly discarded some plants, not wanting to risk the chance that they might harbor a weedy thug in their roots. Plants that could be thoroughly cleaned were happily resettled in the new soil. New selections will be vetted for their ability to play nice and stay put. The new Border will evolve under the watchful eyes of a review committee continually evaluating the plants, not just for control, but for placement and aesthetics as well. Any plant that shows a tendency to become weedy will be removed before it actually becomes a thug. As trees and shrubs grow to specimen size, the plants below them will be changed to suit the increase in shade. The biggest challenge in plant selection has proven to be the native varmints gobbling away at them. Withey and Price had to change much of their planting plans, as many plants proved to be too much like candy for the deer and rabbits.

Mission of Education

Because both the NPA and BBG share an education mission, they are committed to maintaining BBG’s well-built database of plant collections. Having up-to-date, accurate plant records was highly important to the docents who lead tours of the botanical garden. All of the Border plants, both newly acquired and remaining from the previous Border, have been mapped and entered. These detailed maps make communicating easier for the different groups working in the Border.

Long-range goals call for every plant to have its own small, permanent metal label with only the accession number on it. When a plant is in its seasonal prime, a larger label with more information will be placed, and then removed after the plant has peaked. Future plans also call for an electronic kiosk at the top of the center staircase, where visitors will be able to access the plant database.

The two-year Border renovation has beautifully achieved what the partnership hoped for: greatly improved soil conditions and irrigation, multiple pathways for volunteers and visitors to get closer to the plants, benches for relaxed contemplative viewing of the garden, a planting design with orchestrated highlights throughout the year, and the entire Border now seamlessly integrated into the existing—and future—botanical garden master plan.

I have cherished the opportunity to participate in this renovation process. Hearing all the positive comments from visitors and watching as they experience the new Border makes all the debating and rain-drenched workdays more than worth it. It is heartening to see so many dedicated participants, from so many corners of the gardening community, come together to keep this crown jewel sparkling.

If You Should Like to Visit . . .

The Bellevue Botanical Garden, open from dawn to dusk every day with free admission, is located at 12001 Main Street, Bellevue, WA 98005. The Visitor Center is open daily from 9 am to 4 pm. A plant cart with choice divisions from Border plants is outside the gift shop, with proceeds going to support the NPA Border. To access the Online Searchable Plant Database, visit www.bellevuebotanical.org. For more information about the NPA Border, or to join or make a donation, visit the NPA website at www.n-p-a.org.