Drew Asbury is the horticulturist responsible for the greenhouses, the cutting garden, and the horticulture volunteer program at Hillwood Estate, Museum & Gardens, the former Washington, D.C., home of businesswoman and philanthropist Marjorie Merriweather Post. He kindly answered questions from Stroll Avenel about the property, the volunteer program, and some of the pollinators at Hillwood.
We've been running a series on conservation gardening inspired by the conservation garden established at the Avenel Community Center by McFall & Berry. Please tell us about the gardens at Hillwood, particularly about the best pollinators to lure birds and beneficial insects.
About half of our 25-acre property is laid out as a series of garden rooms, while the other half is natural woodlands buffering us nicely from the surrounding city. In the mansion, visitors enjoy Post’s collections of French decorative art and Russian imperial art. Outdoors, visitors can wander through formal garden spaces such as the French parterre and rose garden or to less formal spaces, including a Japanese-style garden, various woodland walks, or the cutting garden. With regard to wildlife and pollinators, two gardens, in particular, the cutting garden and our new native garden, really stand out as our premier examples of habitat. I will start with the cutting garden since that is the garden I have been gardening in and managing for the past ten years.
Marjorie Merriweather Post installed the half-acre cutting garden in the mid-1950s to supply the mansion with an endless supply of fresh-cut flowers. Today, the cutting garden still provides our floral designer with about 500 fresh-cut stems weekly during peak season and provides our 80,000 visitors each year with inspiration on designing and maintaining a pollinator-friendly garden at home. With over 350 cultivars of flowers in the garden, there is always something in bloom for visitors and wildlife to enjoy. See a regularly updated list of what is blooming at the moment at Hillwood at: www.hillwoodmuseum.org/gardens/whats-bloom.
As with all the gardens at Hillwood in recent years, the design, plant selection, and maintenance strategies in the cutting garden are shifting from a purely traditional horticulture regime to a more sustainable and environmentally friendly regime. The garden is currently in its fourth season of being managed organically. The use of traditional pesticides (insecticides, fungicides, and herbicides) and chemical fertilizers have been either completely eliminated from the garden or replaced with a sustainable and organic alternative, such as replacing traditional fungicides with our home-brewed compost tea to help combat powdery mildew and other pathogens on disease-prone plants such as dahlias, zinnias, and peonies.
We also plant the garden much thicker and fuller these days, which helps in a variety of ways. It creates the potential for more flowers over a longer period of time. Intermingling perennials, annuals, and bulbs within a row directly compete with and takes up the space where weeds would likely grow. And finally, it creates ample space and homes for wildlife of all sorts.
Another sustainable shift in the garden was the introduction of a variety of native plants. Native plants further maximize the garden’s ecological potential as native plants support a wider array of wildlife than non-native plants. Some of my favorite native additions are Asclepias tuberosa (butterfly milkweed), Penstemon digitalis (beardtongue), Amsonia hubrichtii (Arkansas bluestar), Pycnanthemum muticum (mountain mint), Eupatorium dubium (joe-pye weed), Rudbeckia fulgida (black-eyed Susan), Echinacea purpurea (coneflower), Stokesia laevis (stoke’s aster), Anemone virginiana (thimbleweed), and Monarda fistulosa (bee balm), and Eryngium yuccifolium (rattlesnake master). In reality, there doesn’t have to be a big difference between a cutting garden and a pollinator garden, and there is no reason why a cutting garden cannot be filled with 100% native plants.
But it’s more than just planting native plants. It's also about how we maintain the garden. Besides eliminating pesticides, we manage the garden in a manner that allows insects and other wildlife to complete their lifecycles and reproduce. For the first time this past winter and spring, we allowed a great deal of the herbaceous material in the garden to remain upright and in place all winter to provide shelter for overwintering insects. Leaf litter, hollow stems, and other garden "debris" make excellent homes for insects during the cold winter months. This material was allowed to remain in the garden until late March/early April. At that time, I "chopped and dropped" all the brown foliage and stems from the previous season by chopping them up with garden shears and allowing them to drop to the ground to make a mulch in the garden. There are many ways our gardens can support pollinators!
We understand Hillwood has established a new garden as well.
Planting began in Hillwood’s newest garden, the native garden at the collections and research center, in 2020, and it is Hillwood’s premier example of conservation landscaping. The garden is entirely composed of native plants and also features a stormwater retention basin, which collects and filters stormwater runoff – yet another fundamental element of ecological gardening. The garden was designed to ultimately become a woodland garden composed of many layers of plants, including a fully developed canopy layer, an understory layer, a shrub layer, an herbaceous layer, and finally, a groundcover layer. Each of these vegetative layers is vital in ecological design, as each is able to support its own array of wildlife. Quercus rubra (red oak), Fagus grandiflora (American beech), and Prunus serotina (black cherry) will contribute to the restoration of the forest canopy, while underneath in the understory, visitors will find Cornus florida (flowering dogwood), Cercis canadensis (redbud), and Sassafras albidum (sassafras).
One of my favorite shrubs in the new garden to attract pollinators is Clethra alnifolia "Hummingbird" (summersweet). It is an easy-to-grow, dwarf, suckering shrub with very fragrant white flowers in July. It attracts a ton of pollinators! Combinations of 50 different native perennials, ferns, grasses, carex, and other groundcovers planted in large repeating masses and drifts will eventually cover the ground providing endless habitat opportunities for a variety of wildlife. These drifts of herbaceous plants will also provide us humans with an almost continuous floral display from early spring through late fall to enjoy! Spring blooms of Phlox stolonifera (woodland phlox) and Geranium maculatum (cranesbill) will be replaced in summer with Chelone lyonii (turtlehead) and Lilium canadense (Canada lily) and finally later in the fall with Eurybia divaricata (white wood aster) and Symphiotrichum cordifolium (blue wood aster) … just to name a few! Be sure to check out these pollinator-friendly gardens during your next visit to Hillwood.
For more information about ecological gardening, a wonderful and informative resource for gardeners of all levels of experience is Nature’s Best Hope by Douglas Tallamy and his corresponding website, ‘Homegrown National Park.’ I cannot recommend these resources enough to anyone interested in helping pollinators and other wildlife in their very own backyard.
Please tell us about the volunteer opportunities you have in the gardens.
Hillwood has approximately 350 volunteers in a variety of positions, including visitor service volunteers, garden and house docents, and horticulture volunteers. About 80 garden volunteers help the horticulture staff throughout the gardens and greenhouse doing what gardeners do: weeding, watering, planting, grooming, and more weeding! Hillwood’s website is the best place to check out which volunteer roles are currently available.
Please tell us about upcoming late summer and fall events.
There is always something going on at Hillwood for visitors to enjoy. On August 19, Hillwood's Floral and Event Décor Designer Ami Wilber will hold a garden-to-table floral design class, and participants have the option of ordering flowers, greenery, and a container and collecting them from Hillwood on the morning of the program. For more on this program, see www.hillwoodmuseum.org/events/garden-to-table-virtual-floral-design.
Our current exhibition, Grace of Monaco: Princess in Dior, is on display through Jan. 8 and features fashion and mementos from the legendary life of Princess Grace of Monaco. Garden and house tours are also regularly available. Details of the exhibition and garden tours, along with an entire calendar of events and activities, can be found on Hillwood’s website: www.hillwoodmuseum.org.
Hillwood Estate, Museum & Gardens
4155 Linnean Avenue, NW.
Washington, D.C. 20008
Washington, D.C. 20008