Yesterday I spent a delightful evening at Mt. Cuba Center in Hockessin, Delaware, touring both the gardens and their fascinating trial plantings of native perennials (more on those in my next post!). This time of year, flowers are few and far between in shady spots, so I wanted to point out two natives worthy of being more widely planted.
Above: Bottlebrush buckeye (Aesculus parviflora)
The first is one of my favorite shrubs, Aesculus parviflora, commonly known as bottlebrush buckeye. This is a robust suckering shrub that ranges from 8 to 12 feet tall and spreads to 15 feet, so plant it in a spot where it will have plenty of room.
Plants produce lacy clusters of white flowers in June or July, and they thrive in part to full shade. As the many specimens at Mt. Cuba illustrate, bottlebrush buckeyes produce denser growth and more flowers when given a site with good light. Still, even when they are planted in shade the delicate white plumes are gorgeous against green foliage.
Although perfectly hardy in our area, bottlebrush buckeye is what I refer to as “nearly native” in my book Chesapeake Gardening & Landscaping (Publication: University of North Carolina Press, spring 2015!), since the species is found growing wild primarily in the Southeast. The flowers attract butterflies, and plants are happiest in average, moist but well-drained soil. They are slow to establish and require regular watering for at least the first season until the roots have had time to spread and delve deep into the soil. After that, they are quite tolerant and can grow in wet soil or dry. Fall foliage is yellow.
Above: Use bottlebrush buckeye in shrub borders, mixed plantings with large perennials, and woodland gardens. Be sure to provide plants with a site where they will have plenty of room to spread, and be patient while they become established.
Another summer standout that I noticed while wandering the pathways at Mt. Cuba was golden or cedar glade St. Johnswort. This is a 3- to 4-foot shrub that spreads to 4 feet and bears yellow flowers.The plant at Mt. Cuba was a blue-foliaged selection labeled Hypericum frondosum ‘Blue Form’. Like the cultivar ‘Sunburst’, which is widely available, it bears showy yellow blooms that resemble tiny shaving brushes. For me, though, the blue-green leaves set it apart. I hope ‘Blue Form’ will be available some time in the future.
Above: Hypericum frondosum ’Blue Form’
Plants grow in full sun to partial shade and prefer average to sandy soil that is well drained. Established specimens tolerate drought.
I would love to see a specimen in my garden combined with seersucker or plantain-leaved sedge (Carex plantaginea), ferns, and perhaps a hosta such as ‘Dick Ward’ or ‘Paul’s Glory’, with leaves variegated in gold and dark green.