Perennials are plants that bloom every year and don't have woody trunks like trees or shrubs, and they are some of my favorite ornamental plants for the summer garden. Unlike early-flowering perennials, summer-flowering perennials tend to have a longer ornamental season. Many flowers continue to bloom for several weeks, providing consistent color as well as pollen and nectar for beneficial insects like bees and butterflies. They can also provide interesting foliage and structure to your summer garden.
When choosing plants for your garden, it's important to consider not only the flowering period and flower color but also the growing conditions of the plants. Is there enough sun (at least six hours of direct sunlight per day)? Is the soil in your garden moist and rich in organic matter, or is it dry and sandy? Once you understand the growing conditions in your garden, you can begin to choose plants based on aesthetic or ecological preferences. The following short list of summer-flowering perennials includes a description of each plant's ornamental characteristics and growing conditions, as well as a note or two about ecological characteristics, such as whether it is a host plant for beneficial insects such as pollinators.
Cardinal Flower (Lobelia cardinalis) Cardinal flower is a midsummer-flowering perennial with bright red flowers. It grows naturally in wetlands, along streams and rivers, and in sunny marshes. In the garden, it grows best in sunny soil with ample moisture. This flower is characterized by its vibrant color, which attracts hummingbirds and many types of butterflies. Horticulturists have crossed red and blue cardinal flowers, resulting in many cultivars of the flowering plant that exhibit characteristics of both species. Unfortunately, research conducted by Dr. Annie White has demonstrated that hybrids may have lower nectar quality and may be less useful to hummingbirds than the natural species. For this reason, if you are planting cardinal flowers to help hummingbirds, avoid cultivars.
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Purple Joe Pie Weed (Eutrochium purpureum)Purple Joe Pie Weed is a tall perennial plant in the Asteraceae family that grows up to 6 feet tall with clusters of pink-purple flowers at the ends of stems in late summer. Like cardinal flowers, it grows naturally on the edges of marshes, but can tolerate a wide range of soil moisture and soil types. Purple Joe Pie Weed's long blooms in late summer make it a great choice for planting in perennial borders. The fragrant flowers attract dozens of species of butterflies and bees.
Roseanne Geranium (Geranium 'Gerwat') Roseanne geranium is a great ground cover with almost iris-like, blue-purple flowers that bloom all summer long. There are many species of geraniums, including the spotted cleansingsbill (Geranium maculatum), a native New England wildflower. In contrast to the common annual “geranium” (not actually a geranium, but a genus of related plants called pelargoniums), Roseanne geranium and spotted cleansingsbill are perennials that return each year after a winter dormant period.
Milkweed (Asclepias incarnata) Milkweed (Asclepias syriaca) has a deserved reputation as a weed in all but the wildest gardens. It is highly adaptable, spreads easily by seed, and is difficult to remove once established. However, like all milkweeds, it is the only food source for monarch butterfly larvae. Fortunately, there are several other milkweed species that are suitable for use in traditional gardens. In the wild, milkweed is found in moist soils, from lake shores to moist grasslands. It is considered an obligate wetland species, and its presence indicates that the area is in fact wet. Despite its natural habitat, it grows very well in moist, average garden soils. It produces beautiful pink to light purple flowers that are highly fragrant.
Broadleaf Mountain Mint (Pycnanthemum muticum) Broadleaf mountain mint is one of six species of mountain mint found in New England. A member of the mint family, the leaves and stems have a minty scent to the touch. They also attract pollinators and provide an important nectar source for native insects in mid-to-late summer. The flowers are white with colored specks and grow in clusters at the ends of stems about 2 feet tall. Just below the flowers are silvery bracts that give them a light, dusty appearance and brighten up the stem tips, which are covered with pale green leaves.
Gardening Central Mass. is written by Grace Elton, CEO of the New England Botanical Garden at Tower Hill, and other horticulture experts. Located on 200 acres in Boylston, the New England Botanical Garden creates plant experiences that inspire people and improve the world. For more information, visit www.nebg.org. This column is published on the third Sunday of each month.
