10 Years and 10,000 Perennials

By: Bob Lilly

Bob Lilly is one of the original designers of the Northwest Perennial Alliance Borders at the Bellevue Botanical Garden. By…

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In spring, the strong form of one of the original apple trees and the brightly colored stems of Salix alba subsp. vitellina provide a backdrop for drifts of Narcissus (Poeticus) 'Pipit', mounds of Ranunculus ficaria, and the emerging maroon shoots of herbaceous peonies; the arching rebar supports will hold roses above the plantings in summer. Photographs by Lynne Harrison

In spring, the strong form of one of the original apple trees and the brightly colored stems of Salix alba subsp. vitellina provide a backdrop for drifts of Narcissus (Poeticus) ‘Pipit’, mounds of Ranunculus ficaria, and the emerging maroon shoots of herbaceous peonies; the arching rebar supports will hold roses above the plantings in summer. Photographs by Lynne Harrison

By virtue of its matchless perennial borders, the Bellevue Botanical Garden attracts eager garden travelers much like a beehive brimming with honey draws bears.

Alice Joyce, West Coast Gardenwalks

In 1991 when we began the original Perennial Border project at the Bellevue Botanical Garden (BBG) the place we are today would have been hard to imagine. Here we are caring for a garden at this stage of maturity, fighting for our survival in the perennial battles of our own devising. From Miscanthus (impossible to dig out of the clay) to Persicaria that spread to infinite proportions and are a constant struggle to control, we have created a complex tapestry worthy of the struggles of the dedicated volunteers from the Northwest Perennial Alliance (NPA).

Hydrangeas in great variety dominate the Shade Border; here, Hydrangea macrophylla 'Hamburg' complements a hardy ginger (Hedychium coccineum ‘Tara’) in autumn

Hydrangeas in great variety dominate the Shade Border; here, Hydrangea macrophylla ‘Hamburg’ complements a hardy ginger (Hedychium coccineum ‘Tara’) in autumn

Developing and managing this project with entirely volunteer labor has been our most significant accomplishment. A great portion of the expenses are covered by sales of plants that our volunteers have propagated from the borders. We now manage 22,0000 square feet in three separate parts: the original Main Border started in 1991, the Shade Border planted in 1995, and the New Border, or West Border in 1997.

How it Started

Members of the Northwest Perennial Alliance wanted to plant a demonstration garden as an expression of our educational mission; we had already done a small drought-tolerant border, designed by Dan Borroff, at the Good Shepard Center in the late 1980s. We felt this project was too limited in size and scope, so we decided to move on to a true perennial border. Nell Scott, a member from Bellevue, was on the original Bellevue Botanical Garden Society board of directors when the Bellevue Botanical Garden was still in the planning stages. She suggested that we approach the city’s Parks Department about our participation in the developing garden there. That subsequently led to a simple contract and a good relationship with them and the then new garden manager, Nancy Park. A site for our perennial border was selected and prepared with our input; we began planting the park one year before the BBG was formally opened to the public.

The level path through the Double Border at the top of the garden provides access to Narcissus (Cyclamineus) 'Jenny', Trillium luteum, and Bergenia; metal hoops protect later emerging perennials

The level path through the Double Border at the top of the garden provides access to Narcissus (Cyclamineus) ‘Jenny’, Trillium luteum, and Bergenia; metal hoops protect later emerging perennials

A Challenging Site

The site chosen for our project sloped down steeply from the main lawn above to a broad gravel path and then down more, eventually merging with the natural woodland below the garden. The project site stretched for nearly 300 feet from north to south along the gently graded gravel path, sloping more steeply at the southern end.

After all the grading and construction was completed on the gravel path, we were left with a sloped planting bed that had essentially no topsoil; it had all been removed in the process of grading the site and pathways to conform to regulations allowing access for the physically disabled. The soil that was left was extremely poor—mostly what we call “golden clay,” a mixture of clay and small rocks which, when fully dried in summer, has the feel of concrete. In that first season of planting, we actually dug some of the holes with a pick. (One volunteer on the first day was never seen again.) At our request, the project manager arranged to have 250 cubic yards of dairy manure placed on the planting bed; our volunteers briefly worked it into the clay.

We also found the slope of the Main Border to be a challenge; it rises about twenty feet from the path at the bottom to the lawn at the top. This does allow for a dramatic layered or tiered effect, particularly in the Hot Border and the sections along the gravel path. The western orientation of this slope results in the flowers of Narcissus always facing the viewer on the path; many plants in the middle of the Border actually flower at eye-level on this slope. The New Border, on the other side of the gravel path, slopes steeply downhill, away from the path, and is even more challenging to plant effectively. Nevertheless, a mixed herbaceous border, such as ours, is not particularly common on a steep slope, so we are able to demonstrate for new gardeners what they can do with similarly challenging slopes on city lots.

Early summer in the Cerise and Gold section, featuring Rosa ‘Henri Martin’ and Weigela Briant Rubidor ('Olympiade') with a massing of Geranium psilostemo

Early summer in the Cerise and Gold section, featuring Rosa ‘Henri Martin’ and Weigela Briant Rubidor (‘Olympiade’) with a massing of Geranium psilostemo

The Layout of the Borders

The Borders were originally designed by a committee of four: Carrie Becker, Charles Price, Glenn Withey, and myself. The plantings were to be organized by color into bays, or sections, along a shrubbery spine which was planted roughly at the top of the slope; roses and smaller shrubs would form the separators between the bays of color. Two color bays are on the flat top of the Main Border, facing the lawn and the visitor center. The remaining color bays are arranged along the lower part of the Main Border and are seen from the gravel path.

The Cerise and Gold section is the most visible from the visitor center; gold foliage and cerise or deep red flowers dominate here. The golden leaves and lipstick red flowers of Weigela ‘Rubidor’ light up the shadows under one of the original apple trees on the property (one of only a few trees in the Borders), joined by Acanthus mollis ‘Fielding’s Gold’, Phygelius aequalis ‘Yellow Trumpet’. We have let Geranium psilostemon seed about in this area to cover the fading foliage on large clumps of Narcissus ‘Pipit’; the geranium flowers through spring and summer.

Peonies (Paeonia), pale silky Shirley poppies (Papaver rhoeas ‘Mother of Pearl’, which seed about readily), and astilbes distinguish the Pink section, against a backdrop of Eupatorium purpureum subsp. maculatum ‘Gateway’ and a deep pink queen of the prairie (Filipendula rubra ‘Venusta’). In early summer, the most notable plants here are a huge clump of the South African fairy wand (Dierama pulcherrimum), flanked by pink masterwort (Astrantia maxima), and the fern-like foliage of Pimpinella major ‘Rosea’.

Astrantia major and astilbes provide a connection to the next section, Variegated and Saturated, with both ferny foliage and pink flowers. In summer, the variegated foliage of Phlox paniculata ‘Nora Leigh’, obedient plant (Physostegia virginiana ‘Variegata’), and money plant (Lunaria annua ‘Variegata’) set the pace here, backed up by a number of intensely blue clematis on tripods.

The Double Path in summer with various hydrangeas, Berberis thunbergii 'Atropurpurea', daylily foliage, Persicaria amplexicaule 'Firetail',  and the golden foliage of Catalpa bignonioides ‘Aurea’ in the distance

The Double Path in summer with various hydrangeas, Berberis thunbergii ‘Atropurpurea’, daylily foliage, Persicaria amplexicaule ‘Firetail’, and the golden foliage of Catalpa bignonioides ‘Aurea’ in the distance

At the southern end of the Main Border, the lawn slopes downhill to the gravel path. Along this southern edge is the Hot Border, continuing the notion of saturated colors but moving into reds and oranges. Daylilies (Hemerocallis) provide a great show here in late June, especially the cultivars ‘James Marsh’ and ‘American Revolution’. This section is anchored by the richly colored foliage of several Japanese barberries (Berberis thunbergii ‘Bagatelle’, ‘Golden Ring’, and ‘Rose Glow’) and backed by more clematis and dark flowered butterfly bushes (Buddleia).

Achillea 'Terracotta' and a daylily (Hemerocallis 'American Revolution') combine in the Hot Border with Persicaria microcephala 'Red Dragon'

Achillea ‘Terracotta’ and a daylily (Hemerocallis ‘American Revolution’) combine in the Hot Border with Persicaria microcephala ‘Red Dragon’

Next to the Hot Border, and tied to it by orange daylilies and golden montbretias (Crocosmia), is the Yellow, Black, And Blue section. This segment of the Main Border is best in early spring, with Narcissus ‘Trevithian’, black mondo grass (Ophiopogon planiscapus ‘Nigrescens’), deep blue squills (Scilla), and Christopher Lloyd’s sassy black-leafed buttercup (Ranunculus ficaria ‘Brazen Hussy’). Summertime finds the striking gold and green variegated foliage of Forsythia ‘Fiesta’ commanding attention.

In the extreme north end of the Main Border is our only totally mixed color section, somewhat segregated from its neighbors by a giant Berberis jamesiana and a Rosa glauca. This section is dominated by asters of various kinds, which need minimal pinching thanks to the local rabbit population.

In the center of the northern half of the Main Border, we have placed a narrow footpath through the middle of the garden, on the upper shelf of the border, which is an extension of the plane of the lawn. Here a stroller on the path is flanked by Acanthus spinosus, white fireweed (Epilobium angustifolium ‘Album’), hydrangeas of various sorts, hostas, daylilies, the colorful flowers and striking seed heads of star of Persia (Allium christophii), and a huge stand of Persicaria amplexicaulis ‘Firetail’, which sometimes threatens to overwhelm the path. These are all overshadowed by a red-leafed Japanese maple (Acer palmatum ‘Bloodgood’), a large green Japanese barberry, Rosa californica ‘Plena’, crape myrtle (Lagerstroemia indica), and pokeweed (Phytolacca americana). When strolling this path, the visitor is truly in the garden.

Midsummer in the Yellow, Black, And Blue section, with Agapanthus 'Bressingham Blue' below the gold and green foliage of Forsythia ‘Fiesta’ and backed by yellow Crocosmia 'Jenny Bloom', daisies, and daylilies (Hemerocallis 'Autumn Minaret' and 'Golden Chimes')

Midsummer in the Yellow, Black, And Blue section, with Agapanthus ‘Bressingham Blue’ below the gold and green foliage of Forsythia ‘Fiesta’ and backed by yellow Crocosmia ‘Jenny Bloom’, daisies, and daylilies (Hemerocallis ‘Autumn Minaret’ and ‘Golden Chimes’)

Success Is Sometimes Surprising

The section we call the Yellow, Black, and Blue has probably held together the best through the years. This section faces due west and is spectacular in the long afternoon light of summer with its golds and yellows, oranges and chartreuse, black mondo grass, and lime green Acorus gramineus. In this area is the best spurge we have: Euphorbia palustris. This species is green-leafed with the typical chartreuse bracts, but has the advantage of dying down to a tight crown each winter, giving the effect of a short Euphorbia characias without becoming woody. A further advantage is that it thrives in our wet winter clay at the bottom edge of the Border.

We have been amazed by a few plants that have proven successful on our water-retentive clay. Tolerance of our soil’s winter wet conditions has become more important that drought tolerance. Among our best and most unexpected performers have been montbretia (Crocosmia), including all of the cultivars except ‘Star of the East’ and ‘Emily McKenzie’, Ranunculus ficaria, Narcissus ‘Salome’, Anthriscus sylvestris ‘Raven’s Wing’, and Sisyrinchium striatum. We have replanted some of the short lived plants when necessary (Anthriscus, Baptisia australis, and the black pansy). Narcissus ‘Trevithian’ and ‘February Gold’ have also done well, along with a number of Miscanthus sinensis cultivars.

For the first eight years, Carrie Becker and I selected and planted 2,000 or more bulbs each fall, so that we now have a spring display worth a visit on its own. The primary focus is on Narcissus, from ‘February Gold’ to ‘Salome’. They are fed in spring to encourage them to establish and naturalize. We have added Ranunculus ficaria cultivars to this spring show as well as masses of double-flowered primroses donated by Valleybrook Gardens five years ago. Of course, it took days to plant 500 of them. And we always seem to be planting Narcissus in December—several thousand bulbs do take a bit of time. Not all the bulbs we planted have been successful; when we planted 10,000 Crocus thomasinianus, all we did was feed the pesky gray squirrels.

Necessity Inspires Solutions

Weeds are a major concern with so much land under cultivation. Planting thickly helps, but the first line of defense against the weeds is mulch; we usually spread dairy manure four to six inches deep and cover about half the garden each year. Our worst problem is the gray squirrels that scatter the mulch as they bury their treasures.

One of our more successful inventions has been the steel supports provided for the shrub roses. As the roses became more established, we needed a way to keep the long arching canes off the perennials beneath and around them. The supports are in the shape of simple candy canes and are made of seven-eighths-inch smooth rebar. They are heavy enough to hold themselves upright in the clay, and their smoothness avoids any bruising of the rose canes when the wind blows. The best ones are cut in ten-foot lengths with a good half circle arc at the top. We made sure to have the upper ends rounded and smoothed, so they would not cut our heads open when we invariably bump into them while pruning the roses and working on the perennials nearby.

We continue to place marble chips around the crowns of hellebores (especially Helleborus x hybridus) and herbaceous peonies to help prevent botrytis. These dark gray (black when wet), small crushed rock chips (used in the creation of terrazzo floors) increase the natural pH of our soil (and mulch). The theory is that a more alkaline soil creates an environment in which the botrytis fungus cannot survive our winters. It seems to be working, and the hellebores like it since the soil becomes more like their native soil. At the Hellebore Open House, held at the Garden each February, we not only sell seedlings from the Border, but also small bags of the stone chips—another way we fund the Border Project.

The main structural change from our original design was to add an edging of bluestone on the lawn side of the Main Border. This edging is made of eighteen-inch squares and eighteen-inch by twenty-four-inch rectangles set in a random linear pattern. This has given the Bellevue Parks Department crew a mowing strip for the turf and has significantly reduced our maintenance of the Border’s edge. We can now let the perennials fall on the stone and yet have a nice clean edge for the lawn. So far this hard sandstone has stayed moss-free.

Our Ongoing Commitment

The NPA has a contract with the Bellevue City Parks Department. Our responsibility is the care, maintenance, mulching, pruning, and any other aspect of care inside the boundaries of the three sections of the Borders project. This has been a successful arrangement for both the Parks Department and the garden management. We have a representative on the BBGS board of directors who also sits on our board. We give presentations about the Borders to the BBGS docents who use the information in the guided garden walks given to visitors.

The Borders are maintained entirely by volunteers, and we now have two weekday crews each month, as well as two Sunday crews. Susan Carter runs a first-Thursday crew with about six gardeners. Sue Buckles’s third-Tuesday crew has recently been inherited by Ann Hobson with knowledge and enthusiasm. These weekday groups offer NPA members an alternative to the original Sunday crews and help us expand the hours we give to the project.

The BBGS gift shop at the garden sells seeds from the NPA seed exchange for a dollar per packet, providing support for the Border project. More than half of the seeds in the seed exchange come from the Borders, including seed from our open-pollinated but seed-parent selected hellebores.

Some might ask: “Why continue with such a long-term project?” To a degree, inertia keeps us going, but there is a tremendous sense of satisfaction in doing complex, difficult, constant, physical work—especially when it leads to a spectacular outcome. The pleasure of this accomplishment is its own reward. Often, at the end of the crew days, a walk around the Border tossing out slug bait (like Van Gogh’s “The Sowers”) can be a weary but joyful chore. Some days, we walk around before and after work session and take time to enjoy what we have achieved—and see what is yet to be done.

By far the greatest pleasure, however, comes when someone says that they appreciate what we have done here in the NPA Borders at the Bellevue Botanical Garden.