Astilbe, commonly known as False Spirea, is a shade-tolerant perennial celebrated for its striking, feathery flower plumes that rise above delicate, fern-like foliage. While these plants add texture and vibrant color to a garden setting, the answer to whether they bloom all summer is straightforward. An individual Astilbe plant provides a distinct period of color rather than a non-stop, season-long display. This flowering period is concentrated, but strategic planting allows for an extended appearance of color in the garden.
The Astilbe Bloom Cycle
A single Astilbe cultivar typically maintains its colorful plumes for a duration of approximately three to six weeks, depending on the specific variety and local growing conditions. The plume structure is composed of hundreds of tiny florets that open in succession, which is why the display lasts for a relatively long period once it begins. The bloom period is determined by the plant’s genetics and is triggered by specific temperature and light conditions in late spring or early summer.
Once the initial set of flowers fades, the individual plant does not produce a second flush of bloom. Astilbe species are terminal bloomers, meaning the plant dedicates its energy to a single flowering cycle per season. The spent plumes then begin to dry out and change color, which marks the end of the flower’s display. While the flowers themselves are finished, the stalks remain upright and continue to offer visual interest in the garden.
Selecting Varieties for Extended Color
The only way to create the illusion of a continuous summer bloom is by intentionally planting a sequence of varieties with staggered flowering times. Astilbe cultivars are generally grouped into three categories based on when they produce their plumes, allowing gardeners to plan for color from late spring through late summer. Combining varieties from each group ensures that as one type finishes its display, the next is just beginning to emerge.
Early Season Bloomers
The earliest varieties to bloom are often the Astilbe japonica hybrids, such as ‘Deutschland,’ which typically start flowering in late spring or the very beginning of summer.
Mid-Season Bloomers
These are quickly followed by the Mid-Season bloomers, primarily the Astilbe x arendsii hybrids like ‘Fanal’ or ‘Amethyst.’ The mid-season types represent the peak of the Astilbe display and provide the bulk of the color throughout the middle of summer.
Late Season Bloomers
To extend the color into late summer and early fall, gardeners rely on the Late Season bloomers, generally derived from Astilbe chinensis species. Cultivars like ‘Pumila’ or ‘Visions’ begin their flowering when the mid-season plants are finishing up, sometimes continuing their display into August or September. This deliberate selection and sequencing of early, mid, and late-season types is the practical method to achieve a three-to-four-month period of continuous Astilbe color.
Post-Bloom Management and Appearance
After the vibrant color of the plumes has faded, the gardener has a choice in how to manage the spent flower heads. Unlike many other perennials, removing the dead flowers, a process known as deadheading, will not stimulate the Astilbe plant to produce new blooms. The primary benefit of deadheading is purely aesthetic, as it removes the browning stalks to maintain a tidy appearance.
Alternatively, the dried plumes can be left in place, where they transform into stiff, tan to caramel-colored seed heads. These dried stalks provide textural contrast and vertical structure in the garden, particularly valuable during the late fall and winter months.
Even without flowers, the Astilbe plant maintains a pleasing presence in the garden due to its foliage. The leaves are deeply cut and fern-like, often emerging in shades of bronze or red before maturing to a deep green. This attractive foliage provides a fine texture that contrasts well with broader-leaved shade plants, ensuring the perennial remains an asset long after the flowering season has passed.