April 24, 2023 – Author’s Note: This article has been corrected. It originally misstated a cultivar as Bluebird. I found the original tag still at the base of the plant this spring. It is actually Skyscraper.
Asters are a confusing lot. Many varieties look similar, so it’s easy to mix them up. Also called Michaelmas daisies because they bloom around St. Michaelmas Day (Sept. 29), asters comprise a huge and diverse family. Usually upstaged by their flashier mum companions, asters are frequently passed over. Or they end up as a last-minute addition to the shopping cart. They just don’t get much respect.
That’s a shame, because these beauties are in fact much tougher than they seem. Armed with facts and a bit of luck, they’re relatively easy to grow on in the garden. Let’s start by demystifying them.
With fringelike petals encircling a pink or golden eye, asters (Symphyotrichum) are cheerful to behold and a valued late food source for bees. I love to see masses of wild asters, often along with goldenrod, filling the roadsides this time of year. Their airy clouds of white and lavender seem to drift over the landcape like fog.
Wood and heath asters are native types that I will not be covering here. They are lovely choices for semi-wild meadows, available from native plant suppliers or mail order. With thousands of cultivars out there, I’ve tried to limit my discussion to the most popular.
Most asters sold today fall into one of three groups: New England (novae-angiliae), New York (novi-belgii) and Smooth (laevi). The technical distinctions are less important for our purposes, and there are subcategories too; the main thing to remember is, each main group prefers different growing conditions.
New England group comprises about four dozen cultivars and are the most heavily marketed, and for good reason: they do best in average conditions. Fully hardy, they come in all the usual aster colors except white. Popular cultivars include Purple Dome, Harrington’s Pink, September Ruby and many, many more. New England asters are common at garden centers everywhere.
New York / New Belgium group exceeds well over a thousand cultivars, but only about a dozen are commercially viable in all the aster colors. Especially well-suited for wet sites, New Yorks want an open sunny position on the cool side, with moist soil. They dislike hot sun and high humidity. If you have light or dappled shade next to a stream, pick a New York. But average garden soil that doesn’t dry out will work too.
Smooth / Aromatic group encompasses just four species plus a few crosses, all wildflowers native to North America from Canada to Mexico. They like it dry and rocky with good drainage, and handle heat well. Their foliage has a balsam-like scent, which is said to deter deer.
To recap, the preferred conditions of each group are:
- New England (angliae)- average conditions
- New York/ New Belgium (belgii) – wet, cool conditions
- Smooth / Aromatic (laevi) – hot, dry conditions
When in doubt, choose a New England aster; you can’t go wrong.
The Tricky Thing with Asters
Of course, growing asters isn’t that easy, or you’d already have a yard full of them and you wouldn’t be reading this article. Who among us hasn’t gotten frustrated when an aster we’ve nurtured along struggled to flower, got mildew or simply gave up the ghost too soon?
The dirty little secret about some asters is they are what I call “Goldilocks” plants. If conditions aren’t just right, they pout. Too much heat, water, drought, shade, whatever extreme — and they rebel with poor health. Some are prone to powdery mildew.
The bright side? If you experience a pouting aster, it’s not your fault. The down side is there’s not much you can do about it. Your best bet is to leverage your chances with good care and do your best to put the right cultivar in the right spot.
Once established however, most asters do well. To get them off to a good start, give them as close to ideal conditions as you can: Proper drainage and air circulation, the right soil (depending on the group), water during dry periods, and plenty of sun but not searingly hot. Pinch back before bloom to avoid legginess.
Finally, don’t expect garden-grown plants to flower quite as fully as nursery-grown ones. A looser, more open habit is natural for asters when not forced under commercial nursery conditions. The result is very pleasing, less artificial in my view.
Cultivars to Consider
There are so many cultivars on the market now it’s impossible to keep track of them all. New hybrids are coming out all the time, bred for perfectly formed mounds of solid blooms. Be forewarned that most of these are not hardy and will likely not survive a zone 6 (or even zone 7) winter.
No matter which one you decide on, always check the tag or ask to determine whether it’s a New England, New York, or Smooth variety and situate it accordingly.
Compact Choices
Purple Dome (New England) – I’ve had decent luck with this compact favorite, now going on its fourth year after being fall-planted from a nursery pot. (For more on this topic, see Overwintering Fall Bloomers.)
Purple Dome makes a great foil for any of the warm-toned mums. It is nice with grasses and Montauk daisies, too. At about 2 feet tall, it’s a versatile size that will work most anywhere. Deer will snack on it when young, though, often delaying its flower cycle. So do protect it if you have a deer problem. But overall it’s one of the toughest and easiest to grow.
October Skies and Raydon’s Favorite (Aromatic) – Similar in looks and habit, both are compact choices. Aromatics are native to the Midwest and favor sandy, rocky soils. They top out at just 12 to 18 inches high, producing dense, uniform carpets of light blue flowers in October. Try these in a protected area of a rock garden, or mix in a handful of sand or vermiculite when planting them in a regular bed.
Audrey (New York) – Here’s a short variety with dainty powder-pink flowers and bright gold eyes. Audrey prefers moist soil with part sun, not burning full sun. A lovely selection for a dappled spot. I must try this one!
Winston Churchill is deep fuschia with a brilliant sulphur-yellow eye, purportedly very mildew-resistant. The color combination is a little too garish for me, but it rivals any mum of similar coloring. This choice will command attention!
Large Asters to Consider
By and large, bigger asters do better in a garden setting than the potted hybrids. While you might find a few of these at a good garden center, they won’t be at big box stores, farm stands or supermarkets. Look for them at specialty nurseries and online. These asters tend to sprawl, so an informal setting works best.
Bluebird (Smooth) – Introduced by Mt. Cuba Center in 1994, Bluebird is an improved native widely tolerant of a range of situations, making it tougher than most. It gets 4 X 4 feet and blooms August into early fall, just covering itself with sky blue flowers.
The entry below was corrected on 4/24/23. Originally I thought the plant in my garden was Bluebird. Upon finding the original plant tag while weeding, I realized that the review I gave was actually for Skyscraper, not Bluebird. My apologies! Mistakes happen… Adrienne
Skyscraper (New England) looks almost identical to Bluebird but is in bloom longer. In fact its best feature is its exceptionally long bloom time, from early to midsummer until frost. Flowering gradually increases over the summer until the entire plant is a mass of solid color by September. Mine did really well in 2022 despite drought, heat, deer, and a spring transplant. I have to say, this one surprised me. Five stars!
As you might expect from the name, Skyscraper gets 5 to 6 feet tall and wide, and if it’s anywhere other than full sun, expect it to sprawl or flop a bit. Regardless, give it plenty of room. It doesn’t have to be staked, but I staked mine after the deer trampled it. The foliage stays pest-free and resists mildew well. I love the sof color. Try it with fall anemones, late phlox, goldenglow, sunflowers or tall rudbeckias.
Alma Potschke (New England) – This cultivar is a ravishing shade of carmine red, unlike any other aster. I didn’t have much luck with it myself because the deer kept eating it to nubbins, but a friend across town has a magnificent clump. Lush, prolific and bushy at three to four feet square, it’s a beautiful and unusual choice. So strikingly different!
Barr’s Pink (New England) – A big, bold beauty for the back of the border with other tall companions. Growing to 5 feet, Barr’s Pink features striking 2.5-inch double blooms with a prominent gold disk that turns bronze. A distinctive aster that would look ravishing paired with bronzy grasses like Miscanthus Morning Light or Switchgrass. I really don’t have room for it, but I sure wish I did — maybe I’ll make room.
Miscellaneous Others
frikkartii Monch – The Monch or Frikart’s aster is a lovely but finicky hybrid of European origin. As a non-native it’s less hardy but will usually survive two years in zone 6b/ 7. Monchs are prized for its early bloom period and unfading color. It has silver-dollar-sized, clear blue flowers that set off everything next to it, beginning in July here. The main show is August and it’s over by September. The form is low and twining.
Because Monchs are short-lived and their output can be uneven, I recommend this one with caution. If you get three seasons out of a Monch, you’re beating the average. The reason I list it at all is because a Monch in bloom is just plain lovely. Only you can decide if you want to put up with its here-today-gone-tomorrow temperament. frilly
If you do opt to grow it, place it mid-border and let it scramble and sprawl as you would a cranesbill. When those flowers open, I swear, you will forgive it all its flaws– until it’s a no-show next spring! Still, I love it. Nothing else is quite this shade of blue in mid-August.
Fellowship (New York) – A 3-foot feminine stunner with frilly double petals and a green-gold eye. As long as you don’t let it languish during dry spells, it’s well worth trying. What a beautiful shade of pink! I definitely need to try this marvelous choice.
So get out there and plant some asters, right now! Whether you want to try and overwinter your fall selections or opt for starting with spring natives, I wish you luck and the carefree beauty of aster multitudes in years to come.
