One of the challenges of gardening with perennials is that, unlike annuals, most do not have long periods of bloom. Some, like peonies, are notorious for a flash of glory which can end almost as soon as it begins when the blossoms shatter in the heat or are flattened by heavy rains. While most are longer-lasting than peonies, perennials are not generally known for providing color all season long. Some strategies for dealing with this characteristic of perennials include mixing perennials with annuals, designing gardens that focus more on foliage than on flowers, and mixing a variety of flowering perennials with a succession of bloom times.
But a gardener who is in love with flowering perennials might also be interested in finding perennials with long bloom times. In my Maine garden, I consider perennials that will bloom for eight weeks or longer during the garden season as long-blooming. Achieving this is easy at the genus level. For example, I grow more than a dozen different species and hybrid varieties of hardy geranium, and one or more of these has been blooming in my garden since the first week in June.
Hemerocallis (daylilies) is another genus that provides bloom in my garden for much of the season. This year, my first daylily to bloom was the reblooming variety ‘Happy Returns,’ which opened its first flower the last week in June. I have had daylilies in bloom somewhere in my garden continuously since then. Currently, there are three late-blooming varieties — ‘Autumn Minaret,’ ‘Final Touch,’ and ‘Sandra Elizabeth’ — providing a beautiful display in the fence border. The very late daylily‘Sandra Elizabeth’ did not begin blooming until the first week in September.
But what about individual plants that bloom for eight weeks or longer? This is a greater challenge, but I do have a number of such plants in my garden. One of my long-blooming stars is Geranium x oxonianum; its lovely clear pink flowers first appeared in my deck border the second week in June, and are still blooming there more than 12 weeks later. Another plant of this hybrid in the circular bed bloomed for 12 weeks before going dormant, and new plantings in their first year in the raised bed bloomed for 10 weeks. Various cultivars of Tradescantia virginiana are also long-blooming in my garden. Particularly notable for its longevity is the variety ‘Osprey;’ one self-sown plant of ‘Osprey’ in my deck border has been blooming continuously for the past three months and still has a few unopened buds. Other long-blooming perennials include Astrantia major, which has been blooming in my serenity garden since the beginning of July, and varieties of Heuchera. Heuchera ‘Raspberry Regal’ bloomed continuously for 12 weeks, and one plant of H. ‘Raspberry Ice’ has been blooming in the deck border for the past three months and is likely to continue blooming until frost.
Geranium, Tradescantia, Astrantia, and Heuchera are all plants with small flowers and prominent foliage. Their display in the garden is often a subtle one, especially since their big first flush of blooms is typically followed by sparser flowering. There are other long-blooming perennials in my garden, however, that put on a big showy display for eight weeks or more. Chief among these is the false sunflower (Heliopsis helianthoides), which begins blooming in mid-summer and often continues until frost. One clump of this plant blooming in the holding area, for example, began blooming during the second week in July (9 weeks ago) and are still going strong. Another big, showy plant that is often long-blooming is the tall Rudbeckia lacianata x ‘Herbstsonne’ (‘Autumn Sun’); this plant began blooming at the back of my blue and yellow border 6 weeks ago and is likely to continue until frost.
It’s not possible to create a list of reliably long-blooming perennials, because which perennials will have long bloom periods depends greatly on local climate and conditions. Many gardeners in warmer climates than mine swear by the hybrid Geranium x ‘Rozanne’ as a long-blooming champion, but this plant is not reliably winter-hardy in my zone 5a garden. By contrast, some of the long-blooming perennials in my garden, especially Geranium x oxonianum and Tradescantia virginiana are not heat-tolerant. In warmer climates, these will bloom in late spring and then go dormant in the heat of summer, perhaps to bloom again in autumn. (This is how divisions of both these plants behaved in my zone 6b Gettysburg garden.) But in my cool Maine garden, these will often bloom continuously all summer long. Micro-climates within the garden also matter; several plants that I have growing in different parts of the garden seem to have longer bloom in cooler, slightly shadier locations. Rudbeckia ‘Herbstsonne,’ for example, blooms longer in the partial shade at the back of the blue and yellow border than it does in the sunny fence border, and Astrantia major has bloomed longer in the deeper shade of the serenity garden than in the light shade of the deck border.
It seems likely to me that, with some trial and error, most perennial gardeners can identify perennials that are long-blooming in their conditions. Which perennials have long bloom periods in your garden?