(formerly Aster lateriflorus) is a species of flowering plant in the aster family (Asteraceae). Commonly known as , , and , it is native to eastern and central North America. It is a perennial and herbaceous plant that may reach heights up to and widths up to .
The flowers of calico aster are small compared to most Symphyotrichum species. They have an average of white ray florets, which are rarely tinted pink or purple. The flower centers, composed of disk florets, begin as cream to yellow and often become pink, purple, or brown as they mature. There are roughly florets, each with five lobes that strongly reflex (bend backwards) when open. The mostly hairless leaves have a characteristic hairy midrib on their back faces, and branching is usually horizontal or in what can appear to be a zigzag pattern. Flower heads grow along one side of the branches and sometimes in clusters at the ends.
Symphyotrichum lateriflorum is a conservationally secure species and grows in a variety of habitats. It can be found throughout most of the eastern and east-central United States and Canada. There is also a native population in the state of Veracruz, Mexico. Its late-summer and fall appearing flowers are visited by small pollinators and nectar-seeking insects such as sweat bees, miner bees, and hoverflies. As well as occurring naturally in several varieties, S. lateriflorum has multiple cultivars and has been grown for at least in Europe. Some modern-day cultivars are 'Bleke Bet', 'Lady in Black', and 'Prince'. It has been used by Indigenous peoples of the Americas as a medicinal plant.
Description Symphyotrichum lateriflorum is a clump-forming perennial that grows tall and up to wide. Herbaceous and with alternate leaves, it can have a different appearance throughout its lifespan or a season. For example, a mature or returning plant, or one late in the season, may have one or more stiff stems that reach close to maximum height, several arching branches, and multiple clusters of flowers (inflorescences). An early or first-year plant may have one short and somewhat floppy stem, several large leaves, and end abruptly with one flower head in the center.
Roots The roots of Symphyotrichum lateriflorum have short and woody branched caudices, and can have short rhizomes that may produce offsets. The images of caudices are from dried specimens of that are stored in the New York Botanical Garden (NYBG) Steere Herbarium.
Stems Symphyotrichum lateriflorum has from one to five stems growing from the root base. These stems can be a reddish or purplish color, often with a woody appearance, or a shade of green. Characteristics can depend on the prevalence of sun, with the green stems occurring more likely in the shade.
Slender and wiry inflorescence-filled branches grow from the stems at almost a right angle or in long arches. Shorter branches may ascend rather than arch. Stems and branches can be covered with fine soft hair, but sometimes the amount of hair is reduced farther from the base, mid-stem, or as it goes up the stem. The hair usually grows in vertical lines, particularly on the inflorescence branches.
Leaves Symphyotrichum lateriflorum has alternate and simple leaves. Characteristics vary among leaves on the same plant and on plants in different environments and areas of the range. Leaves occur at the base, on stems, and on inflorescence branches. The farther away from the base the leaves are, the smaller they become, sometimes markedly so. By the time flowers appear, the leaves at the base and stem have often withered or fallen. Leaves have fine, reticulate veins and little to no hair except for the key characteristic of hair on the back, or abaxial, midrib. This abaxial midrib hair sometimes can all but disappear as the plant ages within a season.
Basal, or ground level, leaves vary in shape from oblanceolate, lance-ovate, ovate, spatulate, to nearly circular. They are thin and the least lance-shaped, with a short or no leafstalk. Basal leaf sizes vary, measuring about in length by in width. The surfaces feel slightly rough to the touch, and the edges are wavy or saw-toothed. Leaves may or may not come to a point at the end depending upon their shape.
Lower and middle stem leaves have no leafstalk, meaning they are sessile, or they have a very short leafstalk with wings. The shapes of the stem leaves vary from ovate or elliptic to elliptic-oblanceolate or lanceolate, rarely linear-lanceolate. Sizes become much smaller the farther they grow from the base. In length, they are with widths .
Distal leaves, higher on the stem and on the branches with the flower heads, are also sessile. Their margins are sometimes entire, smooth on the edges with no teeth or lobes. Sizes range from to in length and up to in width. The more distal, the smaller they are, and this change can occur abruptly.
Flowers Symphyotrichum lateriflorum is a late-summer and fall blooming perennial, the flower heads opening as early as July in some locations and as late as October in others. The flower heads grow in arrays called panicles and are racemose. They generally stay on the upper sides of their stalks, which are called peduncles. The flower heads at the ends of the peduncles mature approximately one week before those on the rest of the plant.
Each flower head is about diameter when in bloom, and is either sessile or with a usually hairy (specifically, pilose) peduncle which is less than in length. At the base of a flower head are from one to seven bracts which look like (and technically are) small leaves that grade into the phyllaries.
Involucres and phyllaries On the outsides of 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 lateriflorum are cylinder-bell in shape and usually in length.
The phyllaries are appressed or slightly spreading. The shape of the outer phyllaries is oblong-lanceolate or oblong-oblanceolate, and the inner phyllaries are linear. They are in (sometimes up to 6) unequal rows, meaning they are staggered and do not end at the same point, and they may be smooth or have hairs. The sparsely haired margins of each phyllary may appear white or light green but are translucent or sometimes reddish. The phyllaries have green chlorophyllous zones that are lanceolate, lens-shaped, or diamond-shaped and have green or purplish tips.
Florets Each flower head is made up of ray florets and disk florets in about a one to one (1:1) ratio, the former developing before the latter. The ray florets grow in one series and are usually white, rarely pinkish or purplish. They average in length, but can be as short as and as long as . They are wide.
The disks have florets that start out as cream or light yellow and after opening, may turn pink, then purple or light brown after pollination. Each disk floret is cylindrical or funnel-shaped, in depth, and is made up of , collectively a corolla, which open into lobes comprising of the depth of the floret. The lobes become strongly reflexed (bent sharply backwards) once open.
Fruit
The fruits (seeds) of Symphyotrichum lateriflorum are not true achenes but are cypselae, resembling an achene and surrounded by a calyx sheath. This is true for all members of the Asteraceae family. After pollination, they mature in and become gray or tan with an oblong-obovoid shape, in length with , and with a few stiff, slender bristles on their surfaces (strigillose). They also have tufts of hair (pappi) on the top which are white to pinkish and in length.
Chromosomes Symphyotrichum lateriflorum has a base number of eight chromosomes Diploid, tetraploid, hexaploid, and octaploid plants with respective chromosome counts of 16, 32, 48, and 64 have been reported.
Taxonomy Classification Symphyotrichum lateriflorum is a member of the genus Symphyotrichum, and is classified in the subgenus Symphyotrichum, section Symphyotrichum, subsection Dumosi. It is one of the "bushy asters and relatives". Its basionym (original scientific name) is and it has sixty taxonomic synonyms. Its name with author citations is Symphyotrichum lateriflorum . Swedish botanist Carl Linnaeus, in 1753, was the first to describe what we know today as Symphyotrichum lateriflorum. Subgenus cladogram
History In 1748, Linnaeus' apostle Pehr Kalm traveled to North America from Europe. He stayed for two and a half years studying flora and fauna and gathering specimens for study by Linnaeus, returning home in 1751. Kalm's travels in North America took him to Pennsylvania, New Jersey, New York, and southeastern Canada. One of the samples he gathered was described by Linnaeus as Solidago lateriflora, now the basionym of Symphyotrichum lateriflorum. Linnaeus recorded the specimen's origin as "" (Latin for "It grows in North America"), and that it was provided by Kalm. Linnaeus classified this plant in the genus Solidago which now contains over 130 of the many species known today as goldenrods. At that time, Linnaeus sorted fifteen of his available specimens into this genus and included them in his two-volume Species Plantarum (1753).
In 1789, Scottish botanist William Aiton included Solidago lateriflora in his Hortus Kewensis, the first edition of a catalogue of the plants cultivated at Royal Botanic Gardens, Kew, where he had been the director since 1759. In separate entries, he also described an Aster diffusus, Aster divergens, and Aster miser, all as separate species definitions from Solidago lateriflora. In the section, Aiton referenced the of Linnaeus "". The Plants of the World Online (POWO) entry for Symphyotrichum lateriflorum includes Aster diffusus as a synonym, but not Aster miser or Aster miser . It does include Aster miser which was described by English naturalist Thomas Nuttall in 1818. Nuttall stated that what he described appeared "to be the of Linnaeus, but probably not that of Aiton". Aster divergens is also listed as a taxonomic synonym.
It was not until 1889 that American botanist Nathaniel Lord Britton combined Solidago lateriflora with Aster species, identifying Aster diffusus and Aster miser as the same. This resulted in one species named Aster lateriflorus , with Solidago lateriflora as the basionym, as it had been the first described. Other names and combinations occurred before and after this, but Aster lateriflorus was the only one associated with the original Solidago lateriflora until the broad and polyphyletic circumscription of the genus Aster was divided. Aster lateriflorus was moved to the genus Symphyotrichum in 1982 by Áskell and Doris Löve during their study of plant chromosomes making its binomial name Symphyotrichum lateriflorum where it currently remains. The infraspecies were subsequently moved by American botanist Guy L. Nesom in 1994.
In a 1928 study of Aster lateriflorus and close relatives, while pondering the "endless confusion in the naming of specimens" of this species, American botanist Karl McKay Wiegand noted how environmental differences likely affected leaf and flower head characteristics, causing botanists to name specimens of this plant as different varieties or species when they may not have been. In this study, Wiegand compared characteristics among the specimens which largely had been ignored up to that point, namely, "the exact length of the involucre and the inner involucral bracts, the number of rays, and the shape of the limb in the disk-corolla as well as the length and character of its lobes."
Varieties