Late summer and fall is a time when most gardens (and gardeners) could use a bit of a pick-me-up. And no plants are better suited for the job than the relatively few shrubs that flower in the growing season’s waning weeks. Whether used as single specimens to spice up drab niches, or combined with other colorful fall plants (such as autumn crocus, Japanese anemones, beautyberries, goldenrods, and sourwood) in a collective blaze of autumnal glory, fall-blooming shrubs are essential elements of a four-season garden.
Quite a few fall-blooming shrubs commence flowering in spring or summer, thus providing multi-season display. Among the longest-blooming of this lot is Daphne × transatlantica. A parent (along with Daphne cneorum) of the much more widely grown Daphne × burkwoodii, this small shrub produces flushes of bloom from mid-spring to fall, long after ‘Carol Mackie’ and other burkwoodii cultivars have ceased flowering. With its clustered, frosty-white, fragrant blooms and dainty, blue-tinged, semi-evergreen leaves, it makes an ideal candidate for a pathside or patio planting. Its variegated cultivar ‘Summer Ice’ has creamy-white leaf margins. Plants are hardy to USDA Hardiness Zone 5, and are best sited where their rather brittle branches will not be subjected to extra-heavy snow loads.
More familiar to gardeners are several other shrubs that flower from summer into early fall. Butterfly bush (Buddleia davidii) produces large candles of fragrant flowers in a range from violet to lilac-pink to white. Butterflies adore them. A somewhat cold-tender shrub, butterfly bush is root-hardy to USDA Zone 5, often dying to the ground in the colder sectors of its hardiness range. Even where it’s reliably root-hardy, it usually benefits from a severe pruning in early spring, growing to several feet tall by midsummer. Many cultivars are available, including the outstanding, compact hybrids ‘Ellen’s Blue’, ‘Blue Chip’, and ‘Ice Chip’. This species seeds itself profusely in warmer areas of its range, where it is sometimes considered a nuisance.
Chaste tree (Vitex agnus-castus), like Buddleia davidii, is a large, fragrant-flowered, butterfly-thronged shrub that usually dies to the ground in the northern fringe of its USDA zone 6 to 9 hardiness range (but attains tree-like proportions in warmer districts). The divided, five-fingered leaves are spicily pungent. Steeples of lilac-blue or white blooms appear from late summer to early fall, on stems that grow to several feet in a single season. Notable cultivars of chaste tree include blue-flowered ‘Shoal Creek’ and white ‘Silver Spire’. Vitex fanciers in USDA zone 5 might want to try chaste tree’s hardier relative, Vitex negundo var. incisa, which has more elegant, finely divided foliage and wispy sprays of lilac-blue flowers.
Rose of Sharon (Hibiscus syricacus) is yet another favorite that flowers from summer into early fall. The large, somewhat floppy blooms bear little resemblance to those of their namesake, nor do their lobed, vaguely maple-like leaves. First introduced to gardens in the sixteenth century (or earlier), this large shrub or small tree has given rise to numerous selections with floral colors ranging from blue to violet to burgundy to pink to white. Among the best are the sterile, white-flowered ‘Helene’ and ‘Diana’, which unlike most other cultivars will not self-sow. Hardy to USDA Zone 5, rose of Sharon will recover quickly and bloom if killed back in a severe winter (or if heavily pruned in early spring).
The large, white, cylindrical flower clusters of panicle hydrangea (Hydrangea paniculata) typically appear in midsummer. The cultivar ‘Tardiva’, however, comes into bloom weeks later than most other selections, peaking in late summer and early fall. Lacier and more elongated than those of the familiar peegee hydrangea (Hydrangea paniculata ‘Grandiflora’), the flower clusters are especially large and late on plants that receive a severe pruning in early spring (plants grow to 7 feet tall in one season). This rock-hardy large shrub succeeds into USDA Zone 3.
In contrast to the above shrubs, Thunberg’s bush clover (Lespedeza thunbergii) concentrates all its bloom in September and early October, enveloping its arching branches in a lavish, vibrant display of rose-purple flowers. As with many late-blooming ornamental shrubs, it sometimes dies back in severe winters, returning from the ground to bloom the following autumn. It’s usually sold in the form of ‘Gibralter’, whose 6-foot stems splay under the weight of its prolific flowers. Other cultivars with pink or white flowers are sometimes available. For tidier winter looks, these shrubs can be pruned back in fall and mulched with Fafard Natural & Organic Compost to keep them protected through winter.
Last in flowering time but certainly not in garden value is a species from forests of central and eastern North America. In the wild, witch-hazel (Hamamelis virginiana) forms a large, often straggly understory shrub whose sparse, spidery yellow flowers are hidden among its yellowing leaves from early to mid-autumn. In the garden, however, it’s an entirely different animal – especially in the form of the recently introduced ‘Harvest Moon’. Bearing a showy profusion of relatively large flowers on naked branches, this cultivar’s floral display rivals that of winter-blooming witch-hazels such as ‘Arnold Promise’. Give it a good, humus-rich soil in sun to partial shade and it will develop into a dense 12-foot shrub that acquits itself well even when not dazzling onlookers with its fragrant, sunny blooms. Where space is limited, try ‘Little Suzie’, a compact, 5-foot witch-hazel selection that works well in foundation plantings, hedges, and other tighter niches.