By Niki Jabbour
A well-designed garden provides interest from early spring through late autumn, and beyond if you also select plants for winter structure. But, for the main growing season, much of that interest comes from flowering and foliage plants. Gardeners who want a lower maintenance landscape would be wise to look for perennial plants that are both easy-to-grow and offer a long blooming period. Most perennial plants flower for two to four weeks, but the longest flowering perennials, like coneflowers and catmint, measure their flowering period in months, not weeks.
The Longest Flowering Perennials
When planning a garden with long-blooming perennials, the same basic rules of design apply; choose a mixture of early, mid-season, and late-flowering plants. Of course, you can also affect both the bloom time and length of the flowering period with pruning practices; pinching, deadheading, and shearing. Read on to discover how to encourage months of blooms by combining clever pruning with the longest flowering perennials.
The Early Bloomers:
Catmint ‘Walker’s Low’ (Nepeta racemosa ‘Walker’s Low’, zones 3 to 9). With its relaxed, trouble-free growth habit, ‘Walker’s Low’ catmint is a perfect fit for a cottage garden or rock garden, or the front edge of a perennial border or rose garden. Plus, the plants bloom their heads off from late spring until mid-autumn with a heavy show of purple-blue flower spikes that are extremely attractive to pollinators and beneficial insects. It’s no wonder this drought-tolerant, hardy plant was chosen as the 2007 Perennial Plant of the Year. Once the initial flush of flowers begins to fade, give the plant a haircut, shearing it back by about one-half. Without a trim, the plant will continue to flower moderately, but a good shearing encourages tidy foliage and plenty of blooms that will persist until frost.
Geranium ‘Rozanne’ (Geranium x ‘Rozanne’, zones 4 to 9). I don’t like to throw the term ‘low-maintenance’ around irresponsibility, but with ‘Rozanne’, it’s the perfect description. This hardy plant forms 12 to 18 inch tall mounds of spreading foliage, which is topped from early summer until frost with two-inch wide, violet-blue flowers. After its initial bloom, the plants will continue to pump out a moderate amount of fresh flowers for months. However, if you shear the plants back by one-third after the first blossoms fade, you’ll encourage another heavy show of flowers.
Bleeding Heart ‘Luxuriant’ (Dicentra formosa ‘Luxuriant’, zones 2 to 9). Long-blooming perennials for shady spaces are hard to come by, but this is where ‘Luxuriant’ shines! Growing just knee-high, this hardy selection produces clusters of reddish-pink, heart-shaped blooms throughout late spring and summer. The ferny foliage is also attractive, and makes a nice foil for the old-fashioned flowers. Plant this shade-tolerant perennial in a woodland garden, shady border, or along a tree-lined pathway. Clipping out faded flowers will ensure months of bloom.
Pruning Tip – Don’t be afraid to grab those pruning shears once that initial bloom of spring flowers starts to wind down. Many perennials, like Geranium ‘Rozanne’ will continue to produce flowers all season, but in a lesser quantity. If you want a heavier bloom, shear the plants back by one-third to one-half to push out fresh foliage and flowers.
The Mid-Season Superstars:
Ornamental Onion ‘Millenium’ (Allium ‘Millenium’, zones 5 to 9). The 2018 Perennial Plant of the Year, ‘Millenium’ is a showy selection with grassy foliage and two-inch diameter, rounded flower clusters in a cheerful shade of lavender-purple. The flowers bloom for around six weeks each summer, attracting every bee, butterfly, and beneficial insect for miles around. The one-foot tall and wide clumps are perfect for the front of a perennial border or a rock garden where the ball-shaped blooms can be appreciated. Technically a bulb, this plant is usually sold as a potted perennial and can be planted in spring or fall. Unlike many perennials, pruning doesn’t produce more flowers.
Coneflower ‘White Swan’ and ‘Magnus’ (Echinacea purpurea, zones 3 to 9). Coneflowers are the cornerstone of a summer perennial garden, blooming for months, even in dry, hot conditions, and providing food for butterflies, bees, and other pollinators. There are countless cultivars available to gardeners, but for months of flowers, it’s hard to beat old school selections like ‘Magnus’ and ‘White Swan’. ‘Magnus’ is a classic purple-flowering coneflower, while ’White Swan’ has large blooms with white petals and orange-copper cones. Both flower from early summer into mid-autumn, especially when deadheaded regularly.
Coreopsis ‘Full Moon’ (Coreopsis x ‘Full Moon’, zones 5 to 9). This eye-catching plant is among the longest flowering perennials with a season that stretches from early summer to early autumn. It’s also the first introduction in the new ‘Big Bang’ series of coreopsis, boasting large, soft yellow flowers that grow up to three-inches across. It also has excellent drought tolerance and is popular with the pollinators. ‘Moonbeam’ is another popular long-flowering coreopsis with pale yellow blooms that are smaller, but no less plentiful than those of ‘Full Moon’. With both cultivars, deadhead flowers as they fade to encourage new buds.
Astilbe (Astilbe species, zones 4 to 9). Astilbe stands out among the longest flowering perennials. Besides being super easy to grow, they thrive in both sunny and shaded gardens, and have feathery flowers that offers months of graceful color. And speaking of color, the blooms can be white, lavender, purple, bubblegum, deep pink, apricot, or red, often with bronze or purple foliage as well. The plants form tidy clumps with the flower plumes emerging in early to mid summer and persisting into winter. The plants do appreciate ample moisture and regular watering in dry summers can prolong the blooming period. Outstanding cultivars include ‘Bridal Veil’, ‘Pumila’, and ‘Fanal‘.
Yarrow (Achillea millefolium, zones 3 to 9). A butterfly favorite, yarrow is a robust summer bloomer with pretty, flat-topped flowers that bloom for 6 to 8 weeks. The ferny foliage emerges in early spring and is followed by the two to four-foot tall flower stems in early summer. Yarrow is one of the longest flowering perennials that grows best in full sun with well-drained soil of average fertility; over-fertilizing can cause the stems to flop over. Flower colours can range from soft pastels to rich jewel shades. Deadhead spent flowers by clipping the flower stem back to the main foliage. Top varieties include ‘Moonshine’, which has pale, yellow flowers and ‘Cerise Queen’, a bright cherry-red bee magnet.
Pruning Tip – As summer flowers fade, deadhead often, cutting down to a fresh stem or set of leaves. This will push the plants to continue producing more blooms. Small flowered perennials, like ‘Moonbeam’ Coreopsis, can be quickly and easily deadheaded with hedge shears, rather than snipping individual blooms. In late summer, as flowering winds down, stop deadheading to allow some blooms to go to seed. Seedheads provide valuable food for birds and add interest to the winter garden.
Fantastic Fall Flowers:
Black-eyed Susan ‘Goldsturm’ (Rudbeckia fulgida ‘Goldsturm’, zones 3 to 9). Widely considered to be among the best perennials of all time, ’Goldstrum’ lights up the late summer garden with weeks and weeks of bold color that persists into October. Each coneflower-shaped flower has a raised chocolate-brown center cone that is surrounded by golden petals. The drought-tolerant plants grow about two-feet tall and offer the best visual effect when planted en masse. Deadhead faded flowers to prolong the bloom period.
Purple Flame Grass (Miscanthus sinensis ‘Purpurascens’, zones 3 to 9). Maiden grasses add striking form and texture to the perennial border all summer long. By late summer, many cultivars produce soft, feathery plumes that emerge above the narrow foliage. Purple Flame Grass is a medium-sized maiden grass, growing three to four-feet tall with foliage that turns from bright green to fiery reddish-orange in early autumn. The attractive plumes are silvery-white and persist on the plants throughout winter. Plant it in a sunny site with well-drained soil. Pruning is only necessary in early spring when the dried foliage and flower stems from the previous season are cut back before the fresh growth emerges.
Pruning Tip – In late spring, pinch out the tips of late summer and fall blooming perennials like sneezeweed, Joe Pye weed, Russian sage, and Sedum ‘Autumn Joy’. Pinching will slow flowering and produce bushier growth, which means more flower-bearing stems.
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