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Fall arrives, in full flower

A longer growing season means hardier perennials

Some perennials, such as rudbeckia (better known as black-eyed susan), provide repeated flushes of bloom throughout the fall if dead flowers are cut off. Some perennials, such as rudbeckia (better known as black-eyed susan), provide repeated flushes of bloom throughout the fall if dead flowers are cut off. (PAT GREENHOUSE/GLOBE STAFF)
By Carol Stocker
Globe Correspondent / September 23, 2010

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Fall is our most spectacular season — and our shortest. But it’s getting longer. When I planted my garden 30 years ago, the first frost of the year wiped out most of the flowers in early October. Now, first frost often doesn’t occur until November, presumably because of climate change. This longer blooming season increases the types of flowers worth growing for fall, good news for adventurous gardeners who’ve tired of the same old cushion chrysanthemums sold at every grocery store.

The biggest change that comes with the longer fall season is that tropical plants no longer get killed before they get blooming. Boston gardeners are now growing banana trees, giant dahlias, crazy towering cannas, and decadent daturas, all of which put on a great fall show before they are killed by cold or brought indoors. Autumn in New England never looked like this before.

The most beautiful of all fall perennials is the Japanese anemone variety Honorine Jobert, which looks like a white poppy on a four-foot stem. This sport, or offspring, occurred at a French nursery in the 1850s. Though the plants are cold hardy, the flowers are not. Most years these late-blooming flowers were shriveled by frosts while still in bud, so it was seldom seen here. But now it blooms reliably almost every fall. The same is true of all the several kinds of fall anemones. I grow the small pink anemone vitifolia Robustissima because it is easy, prolific, and never gets browsed by deer.

Because I love fall, I’ve made a quest of finding unusual autumn blooming perennials. My favorites include Canadian Burnet (Sanguisorba canadensis), which has tall white candles, and Autumn Monkshood, which has equally tall spikes of blue flowers similar to delphiniums, but much easier to grow. The most popular and easiest fall perennial is sedum Autumn Joy (which looks like pink broccoli) and its close relatives.

The most famous native perennial for fall is the New England asters which dot our roadsides at this time of year. There are many species, including the shade tolerant little white wood aster (Aster divaricatus). I used to pull this out as a weed until I saw it carefully cultivated in the renowned White Garden at Sissinghurst in England. My favorite variety of cultivated New England aster is a fuchsia pink screamer called Alma Potschke. The long bloom blue Frikart’s aster didn’t used to be hardy here, but now I can grow it on a south facing slope.

The perfect wildflower complement to blue and pink asters is goldenrod. But do you really want this beautiful thug in your yard? It’s gorgeous and does produce the last sip of nectar for bees and butterflies. But it is so prolific it can take over a garden. So I let it bloom and then cut off the flowers before they go to seed and bag them rather than put them in the compost. And incidentally, goldenrod does not cause hay fever.

Some perennials provide repeated flushes of bloom throughout the fall if dead flowers are cut off (called deadheading) so the plant is motivated to send up new flowers. Fall rebloomers include perennial sunflower (Summer Sun heliopsis especially) and garden phlox such as the lofty white variety David. And if you like the fact that Stella de Oro daylilies rebloom all season, but you don’t like its brassy gold color, look for its sibling, Happy Returns, which is a delicate yellow. Roxanne is a new blue perennial geranium that blooms through fall if you cut the plant back to the basal leaves after each flush of bloom.

And let’s not forget roses, especially the new easy care strains like Knock Out. No shrub blooms as long or as late. They combine beautifully with an underplanting of Roxanne geranium.

Carol Stocker can be reached at stockergarden@gmail.com.