By Melissa O’Brien 

Creating a resilient urban garden that can stand up to extreme urban conditions requires careful thought and planning. The public garden at Logan Square in Philadelphia, which is designed and maintained by PHS, is a great example of how to create beautiful and sustainable urban landscapes for multiple seasons of interest. This location celebrates exuberance in the garden through the thoughtful use of shrubs, perennials and seasonal bulbs, annuals, and tropicals. 

We chatted with Sam Keitch, PHS Manager of Design and Procurement, to learn more about how this garden was created, why certain plants were used, how it continues to evolve over time, and ideas gardeners can use in their own homes. 

Selecting Plants 

Choosing plants for an urban garden is not always straightforward -- there needs to be a consideration for those plants that will be urban tough and resilient.  “Many think that picking a species that will survive urban conditions and has a pretty flower is all there is to it, but the process is about defining a style and a cohesive design as well,” says Sam. It’s important to consider the big picture, including how the space will be used. 

Consider Your Surroundings 

The Logan Square garden offers a visual queue for people to take a moment to appreciate nature amongst the hustle and bustle of city traffic. The intention is to make everyone pause while transforming a public landscape into a gardener’s garden. The entrances and edges of the planting beds are used for more subtle plantings, and these are constantly changing each week as you walk by. Sam says, “The colors of the flowers are combined with a sequential process in mind because each perennial species and cultivar have their blooming window.”  

The larger areas of the garden are more cohesive, featuring flowering mixes, fuzzy foliage that has silver tones, textural foliar displays, including fine and bold leaved plants, and structural and architectural species with height for contrast. The ornamental grasses are the final filler to hold the combinations together, and their flowers and seedheads provide a soft buffer between differing flower shapes. There are many native grass species with shorter varieties that have a major effect when planted in mass.  Home gardeners should take a step back from their intended planting areas to see what colors, textures, heights, and bloom patterns they want as well. 

Consider the Climate 

Many of the grasses used at Logan Square are from harsh climates or have attributes that make them suitable and resilient for specific sections of the garden. “We have had to acclimate with the soil conditions -- some of the taller grasses are tolerant of water saturated soil and others bake along curbsides,” says Sam. Many of the smaller stature species are used to weave together with perennials to lessen the tension between plantings. 

Andropogon gerardii ‘Red October’ has many ornamental moments throughout the season, and the effect begins right when it emerges. “Often, the appealing foliage tones of red, pink and purple creates a stellar performance as the transitioning hues change with the temperature,” says Sam.  Another staple grass species, Panicum virgatum (known as switchgrass), has several cultivars to accommodate a wide variety of settings, and they all retain the same resilient ability to grow in adverse sites. Typically, they prefer poorer soils or disturbed sites, but with many of the newer introductions such as ‘Northwind’, they remain upright regardless of conditions. Home gardeners should consider the amount of sunlight, any traffic (cars, people, or pets!), water needs, and other details for new plantings. 

Use Gold Medal Plants Thoughtfully 

PHS Gold Medal Plants are carefully selected for their ease of cultivation, multiple seasons of interest, commercial availability, appropriateness for the Mid-Atlantic region, and value to wildlife. These criteria make Gold Medal Plants very well suited to urban environments and easy to place in prominent locations within an urban garden. According to Sam, “Gold Medal award winners are dotted around the Logan Square site selectively because although they are all great plants, not all of them fit the aesthetic or conditions of Logan.”  

Vitex agnus-castus  ‘Shoals Creek’ is amazing to tolerate the pressures of the public, and resilient enough to flower every year if it is pruned back to the ground in the late winter. A selection of our native chokeberry, Aronia arbutifolia ‘Brilliantissima’ is great for staggered plantings where you need to frame the view of the garden. Itea virginica ‘Henry’s Garnet’ is exquisite in the fall with burgundy foliage along the southern entrance, and is resilient in multiple environments, including the poorly drained soil that is in the majority of PHS’s managed locations. There are so many classics like Fothergilla x intermedia ‘Mt. Airy’ with white fragrant flowers in the spring as well as newer introductions, like Vernonia lettermannii ‘Iron Butterfly’ grown for its fine texture and dazzling purple flowers in the fall. Gardeners can search the PHS database for all types of criteria before purchasing or planting new varieties. 

Choose Plants that Support Wildlife 

Use a diversity of species so there is always a nectar source for insects and seedheads for food for birds. “We’ve been leaving fruiting bodies intact, especially the coneflowers for the American Goldfinch to eat,” says Sam. “Hopefully one day Logan Square will have the same ecological energy as the Eastern State Penitentiary, which has more of a wild aesthetic and lots of native plants and pollinator friendly species.” 

Source Sustainably 

Whenever possible, try to source plants from local nurseries that have not been treated with insecticides. Many insecticides contain neonicitinoids which kill pollinating insects as they feed on the nectar of plants.  Inquire with your garden centers to find out if the plants they are selling have been treated.  

PHS orders from many local nurseries to tackle the combined bed space at Logan Square, which is around 14,000 square feet. Some plants are added by directly sowing seeds such as the biennial Ceratotheca triloba. Sam mentioned experimenting with using smaller plants, such as plugs for ease of establishment. The ideal model for the future of Logan Square will involve contract growing quart-sized plants to reduce the amount of plants transferred to the site, and then filling in with the very tiny landscape plugs, which are only two inches wide and five inches long.    

Home gardeners should look for smaller sized plants at their local nursery and even check out the bargain bin, because patience is key with establishing a healthy perennial border. You should always plant with ultimate maturity in mind and not immediate impact. 

Design Considerations 

The overall design intent at Logan Square is to preserve the formal elements, while introducing a bold aesthetic. “We have added vertical plants like Juniperus chinensis ‘Hetzii Columnaris’ to create various height levels within the garden, and there are ribbons of permanent plants that are preserved for historical authenticity,” says Sam. The public has responded to the eclectic mixes, and the larger borders are becoming more refined each season. The hardy spines or ribbons, which are drifts of tall grasses and elevated flower heads, run along the Eastern and Western sections. The space will always have annual plantings for a refreshed aesthetic each season, but the pedestrian entrances are intended to be even more complex.  

“Of all of PHS's sites, Logan has had the most effort put in over the decades, and we strive to mirror the progressive plant choice and design trends in the horticulture world, with an emphasis on sustainability, resiliency, and ecology whenever possible. Many of the changes are focused on the longevity of the garden and creating more of a hardy backbone, which lends itself to showcasing the tender material and the changing combinations,” Sam says.   

The garden at Logan Square has become a destination for many residents who stop to interact with the public garden. Tourists are also surprised by the complexity, often stopping to observe the large swaths of color and then realizing that each entry showcases its own design. “People that walk in the corridor of the Parkway often end up walking in circles to see all of the details,” Sam says. “In the future, we’d like to engage the community more and set up more volunteer days.  I think that will be a fitting culmination -- where it is everyone’s garden and anyone in the city is welcome.” Home gardeners are welcome to visit Logan Circle year-round to take photos and enjoy the complex beauty it offers!