6 Perennials for Spectacular Fall Color

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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!

Garden Mums

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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.

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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.

Heirloom Mums

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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.

Asters

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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.

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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.

Goldenrod

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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.

Autumn Sedum

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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.

Turtleheads

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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.

Maiden Grass

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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

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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!20170911a-rachel-kramer-flickr

Coming to Grips with Ragweed

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Deeply cut leaves, reddish stems, narrow green flower spikes? Yep, that’s ragweed (Ambrosia artemisiifolia)!

If you sneeze more often than normal between the beginning of August and the end of September, if your eyes sting, if you’re short of breath and your energy level is close to zero, you are probably suffering from an allergy to ragweed pollen. Hay fever you may call it, although doctors prefer the term seasonal rhinitis. And you’re not alone: in North America, about 10% of the population suffers from hay fever. And ragweed is by far the most allergenic plant on that continent, accounting for almost half of all seasonal allergies.

There are many species of ragweed, always in the genus Ambrosia (Greek for “food of the gods”, a name that was given long before it was understood it caused hay fever!), but it’s mostly common ragweed, also called short ragweed (A. artemisiifolia) that’s the culprit. After all, it’s by far the most common species.

Common ragweed is an annual native to central Canada and the United States, but it spread throughout North America when native forests were cut and replaced with fields of crops, creating an environment similar to the prairies, the plant’s original home. It’s found almost everywhere except in the far north, although populations are moderate on the West Coast and in Atlantic Canada.

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Distribution of ragweed in Europe in 2012. Photo: European Aeroallergen Network

There are no native ragweeds in Europe, but common ragweed has naturalized there as well, probably brought over in contaminated forage seed. It’s been around since the 19th century and is now spreading rapidly and causing serious symptoms in many areas. It’s believed that it will have spread to essentially the entire European continent except the extreme north within the next 35 years.

Small But Harmful

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Common ragweed: the leaves look a lot like those of wild carrot, but are a yellowish green. Photo: Harry Rose, Wikimedia Commons

Common ragweed is a rather insignificant plant from 4 to 38 inches (10 to 70 cm) in height. Its pinnate foliage is deeply cut, much like that of wild carrot or Queen Anne’s lace (Daucus carota), but is yellowish green in color rather than dark green of the latter. Also, it’s usually covered in fine hairs, especially underneath the leaf. Its cylindrical stems are reddish or brownish green, also usually covered in fine hairs. Its flower spike, found at the top of the plant, resembles a very narrow green pagoda … but you won’t see it until the end of summer. The tiny flowers are green or yellowish green too and are not very showy.

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Common ragweed flowers are easily recognizable, but not very striking. Photo: Meneerke bloem,

Ragweed flowers don’t need to have flamboyant colors, as they don’t have to attract insect lr bird pollinators. They are pollinated by the wind. So clouds of ragweed pollen fill the air – and human nostrils – at the end of summer. Each plant can produce up to one billion pollen grains per year, pollen that can travel up to 400 miles (640 km).

The Blame Game

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No, goldenrod doesn’t cause hay fever in spite of beliefs to the contrary. Photo: Olivier Pichard, Wikimedia Commons

For a long time, North Americans blamed goldenrod (Solidago canadensis) for late-summer hay fever. I know my father did: any goldenrod that sprouted on our lot was rapidly put to death! This plant, with bright golden yellow flowers, blooms at the same time as does ragweed and, since the first late summer hay fever symptoms corresponded with goldenrod coming into it’s very visible bloom, it was believed to be the cause of the disease.

Sadly, many people still destroy goldenrod on the pretext that it causes allergies, but in fact it is essentially non-allergenic: its pollen is too heavy to be transported by the wind. Blame instead its inconspicuous cousin, ragweed (both belong to the same plant family, the Asteraceae), whose light-weight pollen is easily carried on the slightest breeze.

Where Does Ragweed Hang Out?

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Ragweed likes bare or nearly bare soil and tolerates poor soils where few other plants will grow. Photo: R.A. Nonenmacher, Wikimedia Commons

Common ragweed is an annual. It has to start from scratch each spring, sprouting from fallen seeds. Unfortunately, its seeds can remain viable for 40 years or even longer. But to germinate, they need sun. As a result, ragweed won’t tolerate competition from taller plants that are already well-established. It instead settles in spots where the vegetation is either low, sparse or absent, thus allowing the sun to reach the ground.

In addition, ragweed is very tolerant of saline soils. In many yards, the place to look for it is along sidewalks, roads and driveways, where grass lawns grow poorly due to applications of road salt over the winter. They kill the lawn or impede its growth, allowing salt-tolerant ragweed to proliferate. You’ll also find it on vacant lots (landfill is not conducive to dense growth of other plants, but ragweed does fine there) and along roads and railways, in parking lots, etc.

You won’t often find it in flower beds or in wooded areas, because the dense vegetation there keeps ragweed from germinating. The use of mulch will eliminate it completely: it simply can’t germinate in a mulched bed.

How to Control Ragweed

If you want to control ragweed, it’s best to start early, in late spring or early summer. Don’t wait until it starts to bloom in late summer.

You could always treat it with herbicides … except that ragweed has become resistant to many common herbicides, such as glyphosate (RoundUp). And obviously, if you garden organically, you won’t want to use herbicides at all. Fortunately, there are other methods.

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Simply mowing ragweed regularly will keep it from producing pollen-bearing flowers.

Since for many homeowners, ragweed is linked to weak or dying lawns near roadways, the best temporary solution is to mow the area frequently. No, this will not kill ragweed plants already present (they’ll sprout again from the base), but at least it will prevent them from flowering. Since common ragweed is an annual, that means it will die with the first hard frosts. Unfortunately, others will sprout in the spring. That’s why mowing can only really a be temporary solution.

For more permanent control, replace weak sod near roadways with either fresh, healthy sod or replace the contaminated soil found there with fresh soil and oversow with quality grass seed. Also, get in the habit, at snow melt, of leaching the soil near the road, letting clear water run for a few minutes to dissolve and carry away salt deposits. That will allow the lawn to grow more densely. And when grass grows densely, ragweed won’t be able to germinate.

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Learn to recognize ragweed when it germinates, as above, and you’ll really be ahead of the game! Photo: weedinfo.ca

If ragweed appears elsewhere on your lot, the easiest action is to pull it out. It doesn’t have a highly-developed root system and is usually easy to yank out. Wear gloves if possible: touching ragweed will not normally provoke dermatitis as long as it’s an occasional thing, but people who regularly handle it can develop contact dermatitis. Yes, another form of allergic reaction!

After you’ve got it out, cover the soil with at least 2 inches (5 cm) of mulch to prevent the seeds from germinating next year or by planting dense vegetation: ground covers for example.

Can You Compost Ragweed?

If the ragweed you pulled out isn’t in bloom, you can add it to your compost bin. But if it is carrying its narrow green flower spikes, be forewarned that the flowers will often mature and even produce viable seed even as the mother plant is dying. Therefore, it’s better to put flowering ragweed plants in the garbage rather than in the compost.


Ragweed should have no place in our gardens.. Make it your duty as a citizen to eradicate it from your own lot… and encourage your neighbors to do so as well!