Plenty of perennial color for August and September

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A good friend who is a great grower with a fabulous garden center filled us in about late blooming perennials that are slow risers in spring, such as blue mist flower (Conoclinum caeruleum also called perennial ageratum). "It's a great plant but really hard to sell. They're nothing but pots of dirt in spring so people walk right be them. We can't afford to waste the display space. And by the time they bloom and people would snatch them up, business is way down -- there are few takers because it's the end of summer." 

Late summer can be wonderful

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in a garden that includes late-blooming perennials. These species come on with fresh color just when we've gotten tired of what's been there for months. Many continue well into fall, after frosts have begun to erase the annual color.

Here are a few you should consider adding, all hardy to zone 5 and colder.





Oh, so many species and varieties, from August blooming Aster novae-angliae (pictured here; it's available in many colors and in heights from 18 inches to six feet) to the aster that waits as long as its name suggests to spangle a garden with tiny white flowers like baby's breath -- that's frost aster (Aster pilosus). Bees and butterflies love them, and if you can put off deadheading and put up with post-bloom shagginess the birds will reward you by brightening your garden as they pluck the seeds. With about 200 native North American aster species, chances are good that at least one belongs in your area, so your planting will also contribute to the local ecology.

Unfortunately rabbits, deer and groundhogs enjoy asters, too, but you can play this card to your benefit. Cage the plants in spring using small-opening wire mesh as tall as you want the finished plant. The browsers will nip it off above and outside the cage, effectively pinching it for you so it blooms a bit later and not too tall!

A note for the technically accurate gardener: Almost every North American aster has suffered a name change recently. This one big genus was split into many! Soon, hard copy references will list them as on-line resources already do, under Symphyotrichum (Aster novae-angliae became Symphyotrichum novae-angliae in this geneticist-driven shuffle), Eucephalus, Eurybia, Oreostemma, Almutaster, Ampelaster, Canadanthus, Chlorocantha, Doellingeria, Machaeranthera, Oclemena and Sericocarpus. Fortunately name change protocol dictates that authors list both old and new name for years so Aster will still be listed for some time to come.

(More about asters on our Aster page...)

Blue mist flowerBlueMist8932.jpg

(Conoclinum caeruleum; syn. Eupatorium coelestinum, zone 5)

It's powder blue in August, smelling of grapes, late to emerge from dormancy but 18" tall at bloom timet and thus perfect for covering up after spring bulbs. Who can dislike blue mist flower? People who want plants to stay put, that's who. We love this plant but others say, "Oh, but it spreads so!"

Indeed it does spread, so use it as a groundcover and rejoice in its mat of shallow, easily identified white roots as you dig out the excess after it's overstepped its bounds.

Above: Even as the flowers age the blue hangs on, extending the season of interest.

Bush clover 

(Lespedeza species, zone 5)

Sturdy, upright, shrub-like perennials, the bush clovers provide a clean background for earlier bloomers, then come on in fall with sprays of pea flowers in pink or white. Lespedeza thunbergii is normally 5 feet tall or more, narrow and upright until bloom and then a fountain of arching canes at bloom time. The dwarf Lespedeza bicolor 'Yakushima' is better suited for small gardens.

Below, left: Purple bush clover (Lespedeza thunbergii)

Lespadiza8182.jpg  Lobelia2321.jpg

Above, right: Lobelia x speciosa, a hybrid created by crossing cardinal flower and great blue lobelia

Cardinal flower, great blue lobelia and their hybrids 

(zone 3)

Native Americans called Lobelia cardinalis "red birds" since a cardinal with spread wings and fanned tail can be seen in each flower on the spike. In woodlands throughout eastern North America, cardinal flower blooms in late July and August alongside great blue lobelia (named Lobelia siphilitica when Europeans noticed it being used by some natives in attempts to cure syphilis -- an unsuccessful application). Complex crosses between the two an another lobelia to produce plants with red-violet and blue-violet flowers and a long bloom season.

Cardinal flower prefers moist sites while great blue lobelia is more amenable to drier soils.


Blue sage, Pitcher sageSalvia0449.jpg

Given other plants to lean on, or a trellis, the North American native blue sage (Salvia azurea) may be 5' tall when it blooms in September and October. Most people are charmed by the color, even if the plant is left to sprawl to 18" and five feet wide.


Toad lilies ToadLily9492.jpg

(Tricyrtis species, zone 5)

Give them shade and be prepared to be delighted as the upright stems begin to spread in a graceful spray by late summer, to display orchid-like flowers all along their length. Many types. They spread by shallow running root so be prepared to give some away if you put it where it is truly happy, in the cool shade.

Every plant should be so clear in its communication as toad lily. Grown in too much sun and heat, the plant remains upright and leaf edges scorch.


More late summer- and fall blooming perennials

Look for these at your garden center, farm market or in a catalog.

S = Sun (6+ hours per day),
HS = Half Shade (4-6 hours sun daily)
SH = Shade, 2-4 hours sun daily
M = Moist soil; water whenever top inch dries
A = Average soil moisture, may dry down to several inches deep between waterings
W = Wet soil, never dries

Allium species  (flowering onion); white/pink; 18-24"; S - SH; M; can be invasive by seed; (curly chives A. senescens, garlic chives A. sativa)

Artemisia species  (wormwood); insignificant flower; 1-5'; S; M, A - D; for grey foliage

Astilbe c. pumila  (Dwarf astilbe); pink; 18"; HS, SH; M, A - W; spreads more than other astilbe

Blackberry lily  (Belamcanda chinensis); orange+; 3-4'; S ; M; each flower lasts one day (candy lily is related x Pardancanda norrisii which is available in many colors)

Blackeye Susan (Rudbeckia species); yellow; 3'; S; M, A - D; self-seeds rapidly

Boltonia (Boltonia asteroides); white, pink; 3-6'; S, HS; M, W

Chrysanthemum (Dendranthema varieties) ; many colors; 1-4'; S; M; many types are not hardy; many bloom late only if pinched

Clematis species  (Virgin's Bower); many colors; 8-30'; HS, S; M, W; shade roots but top needs sun; deadhead large-flowered hybrids; later species (such as C. viticella) are smaller flowered; among the latest to bloom are C. heracleifolia davidiana (fragrant blue bush clematis) and sweet autumn clematis (C. terniflora, invasive by seed)

Culver's root (Veronicastrum virginicum);  white; 4'; S - HS; M, W; may need staking if soil is not moist

Daylily - late hybrids  (Hemerocallis) many colors; 1-4'; S - HS; M, A;
yellow - 'September Gold', 'Golden Prize'
pink: 'Halls' Pink', 'Rhapsody in Pink'
Red: 'Poin Set'

Fall fairy candle (Cimicifuga simplex); white; 24-30"; HS - SH; M

Goldenrod (Solidago species); yellow; 18" - 4'; S - HS, M, A; some species/types are invasive. Not an allergen.

Northern sea oats (Chasmanthium latifolium); flat, green; 2'; S - HS; M, D - A
Blue Oat Grass (Helictotrichon sempervirens); creamy; 2-3'; S - HS; M, A; neat; vertical; almost evergreen
Maiden grass (Miscanthus sinensis); white; 3-6'; S - HS; L; big show in winter; early blooming varieties may be invasive by seed
Perennial fountain grass (Pennisetum alopecuroides); silvery pink; 2-3'; S; M, A; invasive by seed; don't confuse it with tender Pennisetum species such as red fountain grass

Greyheaded coneflower  (Ratibida laciniata); yellow; 4-5'; S; M; needs stakes or sturdy grass to lean on

Hardy hibiscus (Hibiscus moscheutos); red, pink, white; 3-5'; S; M, W; makes a late start in spring - that bare space can be occupied by bulbs

Hosta plantaginea  (old August lily); white; 2'; HS - SH; M; fragrant flower

Japanese wax bell (Kirengeshoma palmata); pale yellow; to 3'; HS - SH; A, W; beautiful foliage

Japanese anemone (Anemone hybrida); white, pink; 2-3'; HS; M, A; blooms later in more shade

Joe Pye (Eupatorium species); violet, white; 3-6'; S; M, A to W by species;
E. maculatum (Joe Pye weed), E. perfoliatum (boneset)

Late gentian (Gentiana septemfida); blue; to 18"; S, HS; M, W

Monkshood  (Aconitum, late species  especially A. carmichaelii, A. wilsonii, A. fischerii); blue; 2-4'; HS, S; M, A; poisonous (all parts, eaten)

Obedient plant (Physostegia virginiana, false dragonshead); pink, white; 2-3' ; S - SH; M, A; can be invasive (variegated type less so); white variety blooms weeks before pink

Pearly everlasting  (Anaphalis spp. A. margaritacea, A. yedoensis, A. triplinervis); white; 12" - 3'; S; M, A - D; dries in place; eaten early summer by American painted Lady butterfly  (which is OK!)

Plumbago (Ceratostigma plumbaginoides); blue; 12"; SH - S; M, A; fall color; emerges late, covers spring bulbs

Sea holly (Eryngium species E. giganteum, E. oliverianum); silver-blue; 3-4'; S; M. D; flowers will dry in place

Sedum x Autumn Joy  (Hylotelephium spectabile, Cabbage Rose) pinks; 18" - 24"; S - HS; M; good cover over summer dormants

Stokes aster (Stokesia laevis); blue; 18"; S - HS; M, A; neat mounded plant, good blue

Tall phlox (Phlox paniculata, P. maculata); pink, white; 3-4'; HS - S; M; fragrant; many types susceptible to mildew

Turtlehead (Chelone species); pink, white; 3'; HS, S; M, W; steady if slow spread but not truly invasive

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