Rice button aster is a perennial herbaceous plant featuring bushy clumps of narrow, lance-shaped leaves. It displays a profusion of daisy-like flowers with yellow centers and pale blue to lavender petals, blooming from late summer to fall. Thriving in full sun, rice button aster adapts to a range of soil types, attracting pollinators while resisting deer in its native meadow and prairie environments.
I. Appearance and Characteristics
Symphyotrichum dumosum (formerly Aster dumosus) is a species of flowering plant of the family Asteraceae commonly known as rice button aster and bushy aster. It is native to much of eastern and central North America, as well as Haiti and Dominican Republic.
This species was long known as Aster dumosus before it was moved into its current genus due to a phylogenetic analysis performed by American botanist Guy L. Nesom. The genus Aster has been narrowed considerably in scope in recent years, due to new information about the relationships of the species in the group.
Symphyotrichum dumosum is classified in the subgenus Symphyotrichum, section Symphyotrichum, subsection Dumosi. It is one of the “bushy asters and relatives.” The word Symphyotrichum has as its root the Greek symph, which means “coming together,” and trichum, which means “hair.” The specific epithet (second part of the scientific name) dumosum is Latin neuter case of dumosus and means “full of thornbushes” and “bushy” (rare).
Symphyotrichum dumosum is a perennial, herbaceous plant that grows up to 1 meter (3 feet 3 inches) high.
Flowers
Symphyotrichum dumosum is a late-summer and fall blooming perennial, with flower heads opening August–October. The flower heads are about 13 millimeters (1⁄2 inch) diameter when in bloom and grow in open and much-branched paniculiform arrays. Each has many tiny florets put together into what appear as one.
Involucres and phyllaries
On the outside the flower heads of all members of the family Asteraceae are small bracts that look like scales. These are called phyllaries, and together they form the involucre that protects the individual flowers in the head before they open. The involucres of Symphyotrichum dumosum are cylinder-bell in shape and usually 4.5–6.3 mm (1⁄5–1⁄4 in) long.
The phyllaries are oppressed or slightly spreading. The shape of the outer phyllaries is oblong-oblanceolate or linear-oblanceolate, and the innermost phyllaries are linear. They are in strongly unequal rows, meaning they are very staggered and do not end at the same point, and they are hairless.
Florets
The 15–33 ray florets are blue, pink, purple, or white, with a length averaging 5–7 mm (1⁄5–3⁄10 in) and width of 1–1.7 mm (1⁄24–1⁄16 in). Ray florets in the Symphyotrichum genus are exclusively female, each having a pistil (with style, stigma, and ovary) but no stamen; thus, ray florets accept pollen and each can develop a seed, but they produce no pollen.
The 15–30 disk florets start out as pale yellow and turn pink with age. They are in the shape of a narrow funnel and are shallow at 3.5–4.5 mm (3⁄20–1⁄5 in) in depth. The disk florets are each made up of , collectively, a corolla, which open into 5 lanceolate lobes comprising less than of the depth of the floret. Disk florets in the Symphyotrichum genus are bisexual, each with both male (stamen, anthers, and filaments) and female reproductive parts; thus, a disk floret produces pollen and can develop a seed.
Chromosomes
Symphyotrichum dumosum has a chromosome number of x = 8. Diploid and tetraploid cytotypes with respective chromosome counts of 16 and 32 have been reported.
Symphyotrichum dumosum has a recorded native presence in the wild in the Canadian province of Ontario, and in the United States in all states east of the Mississippi River except Vermont, as well as west of the Mississippi River in Iowa, Missouri, Oklahoma, Arkansas, Texas, and Louisiana. It is also native on the Caribbean island of Hispaniola.
It is an introduced species in New Brunswick, and in the countries of Belgium, France, Great Britain, Poland, Romania, and Switzerland. It is not on the European Union’s List of invasive alien species of Union concern.
II. How to Grow and Care
Sunlight and Soil
S. dumosum plants prefer a full sun location but can tolerate part shade.
The ideal soil is organically-rich loam, but average quality is also suitable, provided it drains well and has a mildly acidic pH of 5.1 to 6.8.
Watering
Native to moist environments, rice button aster thrives with consistent hydration but is resilient enough to withstand short dry spells. This species has adapted to a balance of moisture, reflecting its preference for well-drained yet damp soil conditions. Watering should be done once every 1-2 weeks, aligning with its moderate drought tolerance. Cultivated primarily outdoors, rice button aster benefits from the growing season’s natural rainfall patterns, which support its cycle of growth and dormancy while maintaining optimal water levels.
Propagation
To grow plants, you’ll need to start with seeds, stem cuttings, or divisions of mature specimens.
You can find complete instructions for starting plants in our guide to propagating asters. Here are the essentials of each propagation method:
- From Seed
To start with seeds, purchase them or collect them from an existing plant. Note that if you collect seeds from hybrids, they may not grow true to the parent plant.
You can start seeds indoors in late winter to get a jump on the growing season.
Alternatively, you can start seeds outdoors after the danger of frost has passed.
Sow the seeds shallowly, barely covering them with an eighth of an inch of soil.
- From Cuttings
When plants are underway in spring and early summer, you can use clean shears to cut a length of five or six inches from the tip of a soft growing stem.
After removing the leaves from the bottom four inches, place the bare stem in four inches of water. Change the water daily to maintain a healthy environment for root formation.
When you see roots forming, you can transplant into the garden or a container.
Or, moisten the bare stem, dip it into powdered rooting hormone, and plant it in a small pot filled with potting medium.
When you see new leaves starting to form, you’ll know the stem has rooted.
- From Seedlings/Transplanting
Before you set your nursery starts or seedlings out into the garden, you’ll need to harden them off first. Do this by placing them outdoors in a protected location for a few hours each day, gradually increasing the time over the course of a week.
The key to success with transplanting seedlings, rooted stem cuttings, and nursery plants is to note how deeply they sit in their containers.
Place them at the same depth in garden soil for a seamless transition, and tamp the soil around them.
Pruning and Maintenance
Whether you are growing wild varieties or hybrids, your plants will likely become a bit leggy. You can prune them early in the summer for a more compact form, but you may adversely affect flower production if you prune too late.
Instead, you can stake plants with twine and bamboo or metal stakes to prevent the stalks from flopping over and risking damage.
If a stalk breaks, make a clean slice with clean pruning shears to sever it an inch or two above the crown. The crown is where stalks and roots come together. Ragged “wounds” make flora vulnerable to pests and disease.
Additional maintenance includes cutting all stalks to the ground and discarding them at season’s end to avoid harboring insects that may overwinter in the debris.
However, if you like the look of the fleecy seedheads as winter approaches, you can wait until late winter to accomplish this task.
In three to four years, you may find that your plants are crowded and/or producing fewer flowers. If so, divide your asters and transplant them as desired.
Dividing not only opens up airspace to inhibit fungal disease; it also rejuvenates flora, improving health and flower production.
Continue this practice as needed, and your plants will reward you with blooms well into the future.
And finally, every spring, when the new shoots appear, fertilize as we did above for a season of vigorous growth.
III. Uses and Benefits
The wild, species bushy aster is suited to open spaces with room to allow it to naturalize informally, without garden borders to dictate its behavior.
If you have a clearing in a wooded area of your landscape, a stream bank, or a perimeter fence, you may want to consider S. dumusom.
In addition to mass plantings that offer expansive drifts of tiny blooms that pollinators and songbirds love, you may want to incorporate bushy asters into a butterfly garden design scheme or add several to a mixed native wildflower collection.
Early in the growing season, the lush foliage forms a green backdrop that makes a good windbreak should you require one.
Today’s dwarf hybrid dumusom cultivars are suited to beds, borders, and container gardening, where their smaller size makes them good mixed arrangement pot mates and stand-alone specimens.
Our guide to aster companions suggests a variety of flora with similar cultural requirements to asters, like goldenrod and joe-pye weed.
