Cushion mums are as spectacular in bloom as any summer perennial. Photo: Rachel Kramer, flickr
You thought the gardening season was over by September and all you had to do was hang up your gardening tools? Think again! Thanks to climate change, in most regions autumns are longer and warmer than ever and that has extended the flowering season well into November, often even December.
Bulbs (colchicums and autumn crocuses), shrubs (several hydrangeas, seven-son flower [Heptacodium] and common witch-hazel) and many annuals (pansies, snapdragons, hybrid sweet alyssums, etc.) will continue to bloom right through the fall, even sailing through the first light frosts. They won’t stop until a truly hard frost hits. In fact, some annuals, like ornamental cabbage, don’t even start to show color until September. But there are more fall-flowering varieties among perennials than in any other group.
Here are six of the best!
Hundreds of years of hybridizing have led to the popular “cushion mum,” with a dense, dome-shaped habit and hundreds of flowers. Photo: pixabay
There are currently about 20 species of Chrysanthemum, commonly called chrysanthemums or just mums, and all are fall bloomers. However, just because they are sold locally doesn’t mean they are hardy in your region.
Many merchants make little difference between florist chrysanthemums (frost-tender varieties) and garden mums (hardy varieties) and sell pots of both in the fall. The two, after all, belong to the same species (Chrysanthemum × morifolium, formerly C. × grandiflorum and Dendrathema × grandiflorum), a complex hybrid with both hardy and subtropical species in its background. Florist and garden mums may therefore appear to be identical, but florist varieties are often only hardy to zone 8 whereas hardy garden mums are solid in gardens as cold as zone 3. That’s a huge difference!
So, how can you tell the two apart in a store display?
In box stores, supermarkets or other non-specialist venues, you can’t. Chances are all the mums they sell are florist varieties, shipped in from the South in full bloom for rapid fall sales. They’re essentially annuals in most gardens. However, garden centers and plant nurseries usually offer both garden and florist types. To find out which is which, ask about guarantees. Truly perennial mums will have a 12-month guarantee; tender florist mums won’t.
Hardy chrysanthemum Mammoth Red Daisy is a big one, as large as many shrubs! Photo: Ball Horticultural Company
There are some very good garden mums (i.e. hardy cushion mums) out there, varieties known for their resistance to extreme cold, and this includes the Morden, Minn, Firecracker and Mammoth™ series (the latter was formerly known as the My Favorite™ series and that name may still be used by some nurseries). The four series offer single and/or double varieties in a wide range of colors: yellow, orange, pink, purple, white, etc. The Morden and Minn mums are dwarf plants (12-18 inches x 18-24 inches/30-45 cm x 45-60 cm) covered with flowers from September to frost, while the Mammoth series mums are taller and wide: 3 to 4 feet (100-120 cm) tall and wide. Firecracker series mums (Power Surge®, Showbiz®, Suncatcher®, etc.) are of intermediate size.
All varieties mentioned are hardy to zone 3. Sun or partial shade.
The most popular heirloom mum is ‘Clara Curtis’. Photo: rosekennedygreenway.org
There are also heirloom mums, also called old-fashioned mums or rubellum mums. They’re a different species: Chrysanthemum × rubellum, formerly C. zawadskii latilobum.
This group includes the well-known ‘Clara Curtis’ (pink, zone 3), ‘Duchess of Edinburgh’ (dark pink, area 4) and ‘Mary Stoker’ (yellow, zone 3), plus half a dozen others. All produce simple daisylike flowers with a yellow center. They reach about 18 to 30 inches (45-75 cm) in height and diameter, depending on the cultivar, but have more finely cut leaves than garden mums and certainly don’t form the dense mounds typical of cushion mums. Instead they have a much more open habit and are even inclined to wander a bit. They’re not really invasive, though, as it’s easy to pull out stragglers if they go too far.
Zone 3. Sun or partial shade.
You can read more about hardy mums here: Chrysanthemums for Cold Climates.
New York aster ‘Patricia Ballard’. Photo: dorsetperennials.co.uk
North American fields and forests are full of wild asters in shades of violet and white, but there also are many cultivated asters to be discovered, including New England asters (Aster novae-angliae, now Symphotrichum novae-angliae) and New York asters (A. novi-belgii, now S. novi-belgii). They have larger flowers in a much wider color range than wild asters. They come in shades of violet (so-called blue), purple, pink, red, and white, often with semi-double or double flowers.
Until recently, most asters were tall to medium-height plants for the back or the middle of the garden. A. n-a. ‘Harrington’s Pink’ (pink, 48 inches x 24 inches/120 cm x 60 cm) and A. n-b. ‘Patricia Ballard’ (dark pink, 36 inches x 15 to 20 inches/90 cm x 40-50 cm) are examples of these popular taller varieties.
Aster ‘Purple Dome’. Photo: Footprints Plants, LLC
Dwarf asters, although often sold under the botanical name A. dumosus (a name that really belongs to a summer-flowering Eurasian species), are actually just smaller selections of A. novae-angliae and A. novi-belgii. A. n-a. ‘Purple Dome’, for example, is popular, forming a rounded dome 16 to 20 inches (40-50 cm) in height and width with purple flowers. The Wood’s series of dwarf asters is similar, but comes in other colors.
Fall asters are hardy to zone 4, sometimes in zone 3. Sun or partial shade.
Solidago rugosa ‘Fireworks’. Photo: F. D. Richards, flickr
There is a surprising dichotomy between the attitude of North American and European gardeners towards goldenrod (Solidago spp.). North Americans tend to see goldenrods, which are native to their continent, as weeds and want little to do with them. Europeans, on the other hand, for whom they are exotic plants coming from the New World, adore them!
I find it almost criminal to malign these gorgeous perennials with their rich yellow flowers simply because they’re natives when, in fact, they are among the best fall perennials. True enough, Canada goldenrod (Solidago canadensis) is highly invasive species in gardens, both through seeds and wandering rhizomes, but the others are clump-forming and stay put. If you don’t believe me, try S. × ‘Crown of Rays’ (23-27 inches x 18-23 inches/60-70 cm x 45-60 cm), S. × ‘Dansolitlem’ Little Lemon® (12-18 inches x 12-23 inches/30-45 cm x 30-45 cm) or S. rugosa ‘Fireworks’ (36-48 inches x 36 inches/90 to 120 cm x 90 cm), all with stunning feathery yellow flowers. Beautiful!
Zone 3. Sun or partial shade.
Sedum ‘Herbsfreude’. Photo: laidbackgardener.blog
Autumn sedum, also called autumn stonecrop, showy sedum or showy stonecrop (cultivars and hybrids of Sedum spectabile [Hylotelephium spectabile] and related species), is a fairly low-growing plant (rarely more than 2 feet/60 cm tall), with succulent stems and leaves, often bluish green. The star-shaped flowers are produced in dense masses, a bit like colored cauliflower, and come in shades of pink, red or white, more rarely, pale yellow. They’re one of the last fall feeding stations for butterflies.
S. ‘Herbsfreude’ (‘Autumn Joy’), 12-24 inches x 18-24 inches (60 cm x 45-60 cm), is best known and bears pink flowers turning brownish red. S. ‘Autumn Fire’ is similar, but more compact (20 inches x 18-24 inches/50 cm x 45-60 cm). A sturdier plant, it doesn’t tend to flop under the weight of its flowers the way ‘Herbstfreude’ may do. S. ‘Purple Emperor’ (16 inches x 18-24 inches/40 cm x 45-60 cm) is just one of many autumn sedums with dark purple leaves and pink flowers, while ‘Elsie’s Gold’ (16-18 inches x 20-24 inches/40-45 cm x 50-60 cm) has green leaves with yellow to cream edges and magenta flowers. It’s less likely to flop than most other variegated autumn sedums.
There are dozens of other excellent varieties.
Zone 3. Sun.
- Chelone lyonii ‘Hot Lips’. Photo: laidbackgardener.blog
Turtleheads get their curious name from their flowers, said to look like a turtle’s head. In fact, their botanical name, Chelone, comes from the Greek and also means turtle.
Red turtlehead (Chelone obliqua) is probably the most common variety. It produces a dense, non-invasive clump of solid, perfectly erect stems 24-36 inches tall on a plant 24 inches in diameter (60-90 cm x 60 cm). The very dark green leaves are attractive all summer, but the beautiful deep pink flowers dominate in the fall.
Lyon’s turtlehead (C. lyonii) is very similar in all respects: you can scarcely tell it apart from pink turtlehead (C. obliqua). C. lyonii ‘Hot Lips’ (60-90 cm x 60 cm) is very popular with darker leaves than the species. C. lyonii ‘Tiny Tortuga’ is a dwarf variety only 12-15 inches tall and 8-10 inches in diameter (30-40 cm x 20-25 cm).
Zone 3. Sun or shade.
Miscanthus ‘Purpurascens’. Photo: laidbackgardener.blog
This tall grass (Miscanthus sinensis) is very popular, grown for its arching green ribbon-shaped leaves that become straw-colored in fall and its blooms that start pinkish to become silver-white as fall progresses. Both leaves and flowers hold on right through the winter into spring, offering six months or more of interest.
In zone 7 and above, maiden grass can self-sow and become invasive due to overseeding, so look for near-sterile varieties like ‘Autumn Light’ and ‘Morning Light’ as well as any of the variegated cultivars, as they almost never bloom.
Seeds don’t mature in cold climates, so maiden grass isn’t invasive there … but it might not perform well there either. Its hardiness varies from zone 4 to 6, so make sure you choose one cold resistant enough for your conditions. Also, some cultivars won’t have time to bloom in short-season climates or will only bloom occasionally in years where the summer was extra-long. Unless your local merchant is a specialist in ornamental grasses, you won’t be warned about this fact, so research your plants ahead of time.
Best choices for bloom in colder climates include the extra=hardy Huron series, including M. s. ‘Huron Sunrise’ (6 feet x 2-3 feet/180 cm x 60-90 cm), zone 3, the popular tall cultivar M. s. ‘Silberfeder’ (7-8 feet x 4 feet/200-250 cm x 120 cm), zone 4, and purple maiden grass (M. ‘Purpurascens’), 5 feet x 2 ½ to 3 feet (150 cm x 75-90 cm), also zone 4. The latter offers distinctly coppery foliage color in fall.
Sun or partial shade.
Even More Fall-bloomers
Add the right fall-bloomers and your autumn garden will come alive!: Photo: autumnasters.co.uk
There are still many other perennials that bloom in fall: boltonia (Boltonia), Japanese anemone (Anemone × hybrida), helenium or sneezeweed (Helenium), bugbane (formerly Cimicifuga, now Actaea), ironweeds (Vernonia), tall coreopsis (Coreopsis tripteris), Joe-pye weeds (Eupatorium), perennial sunflowers (Helianthus ‘Lemon Queen’ and others), black-eyed susans (Rudbeckia), monkshoods (Aconitum), echinaceas (Echinacea), and many more.
As you can see, with the right choice of plants, there is no reason why your garden can’t be as spectacular in October as it was in July!