If your perennial or pollinator garden is missing ‘Storm Cloud,’ this is the year to add it to the display. The native perennials shine with sky-blue flowers, narrow leaves, dark stems, and an adaptable nature. Explore the merits of this top performer with gardening expert Katherine Rowe.
There’s a lot to love about Amsonia ‘Storm Cloud.’ First are its tufts of starry periwinkle blue flowers that hover above foliage in late spring. Next are willowy leaves and a bushy habit that bring contrast and texture to the display. There’s also the advantage of carefree growing with little maintenance needed.
Perhaps most significant is that all this ornamental and ecological value comes from a U.S. native selection. The species is native to the Southeastern part of the country. The flowers and foliage host pollinators, and there’s little demand for excess resources regarding water and fertilizers.
Designated as the 2024 Landscape Perennial of the Year by Proven Winners, ‘Storm Cloud’ also tops plant trials. The heat-tolerant, deer-resistant selection is a valuable perennial addition.
What is ‘Storm Cloud’ Amsonia?
‘Storm Cloud’ is an herbaceous perennial plant with unique blue-hued flowers. It is an exciting discovery among a native species. Amsonia is a small genus mostly native to the United States, with some occurring in Asia and the Mediterranean. A. tabernaemontana, or bluestar, is highly ornamental and the most popular of the group.
‘Storm Cloud’ shines in late spring with loose, whole clusters of periwinkle blue flowers. Attractive, willowy foliage in deep olive green with golden-yellow fall color brings multiseason appeal. Even when the bushy perennials aren’t in flower, they provide a handsome backdrop to summer and fall bloomers.
This native selection grows two to three feet tall and three to four feet wide. Its size makes it ideal for the middle of the perennial border or as a shrub replacement. With their highly decorative flower heads, they’re exceptional in groups and as stand-alone specimens.
Companion Plants
Bluestar embellishes naturalized garden schemes among looser plantings. Contrasting foliage like yarrow, nepeta, heuchera, and hosta anchor the display. Use them to accent the perennial border, native planting arrangement, pollinator, rain, and rock gardens, and woodland edges.
They complement spring-flowering plants like bulbs, lilies, and phlox. Echinacea, hardy hibiscus, salvia, and ornamental grasses add color and movement throughout the warm season.
Awards
This exceptional native is famous for its low maintenance and easy care. The plants are durable and have few landscape problems. Their unique forms enliven the planting arrangement with abundant baby blue florets and rich foliage. Butterflies, hummingbirds, bees, and other pollinators flock to the large, nectar-rich flower clusters.
In addition to the Landscape Perennial of the Year designation, ‘Storm Cloud’ tops plant trials at Michigan (2022) and Mississippi (2021) State Universities.
Characteristics
Sparkling starry blooms are the standout feature of ‘Storm Cloud,’ but the intrigue doesn’t end there. As temperatures warm in the spring, new stems emerge nearly black. They hold their dark color through flowering, lightening as summer progresses.
Willow-shaped leaves densely whorl around the smooth stems. They emerge dark olive green with silver veins. As summer moves to fall, they become lighter green and yellow before turning gold in cool autumn temperatures. They then become brown and dry with winter dormancy.
The plants produce multiple stems that rise two to three feet tall. In late spring and early summer, flowers appear in panicles on the tips of stems, with the potential for reblooming. The flowers are lovely on the stem and in fresh arrangements.
Each ¾-inch tubular floret flares to a pointed star shape. After flowering, elongated bean-like seed pods develop. The fruits dry and split open when ripe.
When cut or damaged, stems produce a milky sap to seal the wound and deter predation. If ingested, the sap is toxic to people and pets and can cause contact skin irritation. On the plus side, deer seldom damage the native bloomers.
Bluestar has few pests or disease problems. It is drought-tolerant and withstands heat and humidity. In optimal growing conditions, it’s a long-lived garden performer.
Native Area
The species tabernaemontana occurs naturally in the Southeast, Eastern, and Central United States. It grows in open woods, thickets, plains, and wet, sandy sites. It spans a range of conditions and climates.
Renowned plantsmen Hans Hansen (Walters Gardens) and Tony Avent (Plant Delights Nursery) discovered the native selection among an Amsonia colony in Bibb County, Alabama. The plants grew wildly in wet, deep shade along a woodland stream. After trials in Michigan and North Carolina, they selected ‘Storm Cloud’ for its robust growth, compact habit, and prolific blooms.
Planting
Fall and spring are the best times to plant perennials. However, if there is adequate moisture for strong root systems to develop, plant them anytime. Avoid planting during stressful conditions like high heat, drought, or freezing soils.
Plan for maturity so bluestar can grow in a permanent garden location. They develop long tap roots and spread 38-42 inches wide.
Dig a hole two to three times as deep and wide as the size of the root ball. Loosen any tightly wound, pot-bound roots so they can grow outward. Water plants deeply to settle the roots and soil.
‘Storm Cloud’ is sturdy and withstands winds and coastal exposures. If exposures are drying, supplemental irrigation helps maintain vigor.
The bloomers also grow well as singular container specimens. Ensure pots are large enough to house their robust roots. Provide consistent water, a quality potting mixture, and good drainage.
How to Grow
This adaptable cultivar is carefree and reliable. With a sunny location and moisture during intense dry spells, it needs little else to flourish. While ‘Storm Cloud’ is mostly self-sufficient, optimal cultural conditions promote the best growth and flowering.
Maintenance
Amsonia needs little ongoing maintenance. Cut back dry stems at the end of the season or leave them in place for added winter protection and overwintering insects. Remove them before or just after new spring growth emerges.
Cut plants back to six to eight inches after flowering to tidy up the plant’s appearance and encourage a new flush of growth. The early summer cut promotes a fresh, rounded form for the remainder of the growing season. It also helps keep stems upright in shadier conditions. Pruning isn’t essential to the plant’s health.
Mulch around plants with a three-inch layer, avoiding the stems. Mulch regulates soil temperatures and improves moisture retention.
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