User:Eewilson/S-next

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Eewilson/S-next
refer to caption
S. pilosum var. pilosum
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S. pilosum var. pringlei

Secure (NatureServe)[1]
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Asterales
Family: Asteraceae
Genus: Symphyotrichum
Species:
S. pilosum
Binomial name
Symphyotrichum pilosum
Varieties[2]
  • S. pilosum var. pilosum
  • S. pilosum var. pringlei (A.Gray) G.L.Nesom
Symphyotrichum pilosum native distribution map: Canada — Nova Scotia, Ontario, and Québec; United States — Alabama, Arkansas, Connecticut, Delaware, District of Columbia, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Nebraska, New Hampshire, New Jersey, New York, North Carolina, Ohio, Oklahoma, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Vermont, Virginia, West Virginia, and Wisconsin
Native distribution of both varieties of S. pilosum[3][4]
Synonyms[2]

Basionym

  • Aster pilosus Willd.
Species
    • Aster chrysogonii Sennen
    • Aster ericoides var. pilosus (Willd.) Porter
    • Aster ericoides var. platyphyllus Torr. & A.Gray
    • Aster ericoides f. villosus (Torr. & A.Gray) Voss
    • Aster ericoides var. villosus Torr. & A.Gray
    • Aster juniperinus E.S.Burgess
    • Aster pilosus var. demotus S.F.Blake
    • Aster pilosus var. platyphyllus S.F.Blake
    • Aster pilosus f. pulchellus Benke
    • Aster villosus Michx., nom. illeg.
var. pringlei
    • Aster ericoides var. pringlei A.Gray
    • Aster faxonii Porter
    • Aster pilosus var. pringlei S.F.Blake
    • Aster polyphyllus Willd., nom. illeg.
    • Aster pringlei Britton

Symphyotrichum pilosum (formerly Aster pilosus) is a perennial, herbaceous, flowering plant in the Asteraceae family native to central and eastern North America. It is commonly known as hairy white oldfield aster, frost aster, white heath aster, heath aster, hairy aster, common old field aster, old field aster, or steelweed. There are two varieties: Symphyotrichum pilosum var. pilosum, known by the common names previously listed, and Symphyotrichum pilosum var. pringlei, known as Pringle's aster.

The varieties differ in morphology, distribution, and habitat; S. pilosum var. pilosum is a hairy variety, and S. pilosum var. pringlei is hairless, or nearly so. S. pilosum var. pilosum is the more widespread of the two and grows in a variety of dry habitats, often with weeds. S. pilosum var. pringlei grows in higher-quality calcium-rich ecosystems, often with many companion flora.

The species usually reaches heights between 20 centimeters (8 inches) and 120 cm (4 feet). It blooms late summer to late fall with composite flowers that are 13 to 19 mm (0.5 to 0.75 in) wide and have white ray florets and yellow disk florets. S. pilosum var. pilosum and the rare endemic Symphyotrichum kentuckiense breed and produce a hybrid that has been named Symphyotrichum × priceae. It also has been found to hybridize with other Symphyotrichum species.

Both varieties are conservationally secure globally, and S. pilosum has been introduced to several European and Asian countries. S. pilosum var. pringlei has been used in the cultivar industry and it and its cultivar 'Ochtendgloren' have won the Royal Horticultural Society's Award of Garden Merit.

Description[edit]

Symphyotrichum pilosum is a perennial that reaches heights between 20 centimeters (8 inches) and 120 cm (4 feet), sometimes as short as 5 cm (2 in) or taller than 150 cm (5 ft).[5] It flowers late summer to late fall, in the north ending in October and farther south in December.[6] There are two varieties: Symphyotrichum pilosum var. pilosum and S. pilosum var. pringlei. They differ in morphology, chromosome count, distribution, and habitat.[5][3][4] S. pilosum var. pilosum is the autonym, with hairy stems and leaves. It is widespread and often weedy.[3] S. pilosum var. pringlei is hairless, less common, and often grows in high-quality habitats.[7]

Roots and stems[edit]

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Stem and leaves

The roots of S. pilosum have bulky and branched caudices that sometimes have long rhizomes. The plant is cespitose with one to five straight stems.[5] The two varieties have different stem surfaces: S. pilosum var. pilosum has hairy stems (pilose to densely hirsute),[3] and S. pilosum var. pringlei has stems with no hair (glabrous)[4] or at most, they are hairy in vertical lines.[5]

Leaves[edit]

S. pilosum has leaves that are thin,[5] alternate, and simple.[8] They differ between the varieties in that S. pilosum var. pilosum has hairy leaves,[3] and S. pilosum var. pringlei's are hairless or nearly hairless.[4] Basal leaves are either sessile or have very short leafstalks with sheathing wings that are fringed with hairs on their edges (ciliate). The basal leaves are oblanceolate or obovate to spatulate with obtuse to rounded tips, and their bases are attenuate. Their margins (edges) are slightly wavy or saw-toothed, mostly near the tips. Basal leaves range in lengths from 10 to 60 millimeters (0.4 to 2 inches) and widths from 5 to 15 mm (0.2 to 0.6 in). They grow in a rosette and develop prior to flowering then wither or die during plant growth. At the time of flowering, another rosette of basal leaves forms.[5]

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Close-up of a portion of S. pilosum var. pilosum showing a cluster of small leaves at a stem node

Lower stem leaves also usually wither by flowering, and they often have small leaves in clusters at the stem nodes. These stem leaves are entire (smooth on the edges) to saw-toothed and have soft cilia. Their tips are attenuate, and the leaves are elliptic-oblanceolate, elliptic-oblong, linear-lanceolate, or linear-oblanceolate. The leaf bases can be petiolate or subpetiolate to subsessile, and they clasp the stem with attenuate to cuneate bases with wings. Lengths are from 40 to 102 mm (1.6 to 4.0 in) and widths from 5 to 25 mm (0.2 to 1 in), getting progressively smaller as they approach the upper portion of the stem.[5]

Distal leaves, higher on the stem and on the branches with the flower heads, are lance-oblong, linear-lanceolate, linear, linear-oblanceolate, or linear-subulate. Their margins are entire or saw-toothed, and they are sessile with cuneate bases. Lengths range from 10 to 100 mm (0.4 to 4 in) and widths are 1 to 8 mm (0.04 to 0.3 in). The leaves get progressively smaller near the inflorescences; closest to the flower heads, their sizes are abruptly reduced.[5]

Flowers[edit]

See also: Asteraceae § Flowers
refer to caption
S. pilosum var. pringlei inflorescence showing a branch with many peduncles, each with its own flower head. The inflorescence is in the shape of a pyramid.

The flower heads of Symphyotrichum pilosum are 13 to 19 mm (0.5 to 0.75 in) wide[8] and grow on branches that are 100 mm (4 in) or less at wide angles off the stem (divaricate). They also may be ascending and arching. They are open, generally not crowded, and have many small leaves. Each flower head is on a peduncle that is usually 5 to 30 mm (0.20 to 1.2 in)[a] long. They get shorter the farther up the branch they grow which then causes the inflorescence to look like a pyramid. The peduncles of S. pilosum var. pilosum have dense and bristly hairs (hispid), and those of S. p. var. pringlei are hairless (glabrous). Both varieties have from 7 to 25 or more bracts that are glabrous and may have cilia.[5]

Involucres and phyllaries[edit]

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Flower heads

Flower heads of all members of the Asteraceae family have phyllaries which are small, specialized leaves that look like scales. Together they form the involucre that protects the individual flowers in the head before they open.[b][9] The involucres of Symphyotrichum pilosum are campanulate to cylindro-campanulate in shape (bell to cylinder-bell) and usually 3.5 to 5.1 mm (0.14 to 0.20 in) in length, although they can be as short as 2.5 mm (0.1 in) and as long as 6.5 mm (0.26 in).[5]

The phyllaries of S. pilosum var. pilosum have small and sparse hairs, meaning they are hirsutulous, and those of variety pringlei are glabrous. Both varieties have phyllaries in 4 to 6 unequal rows, which can be subequal, although this is rare. They are appressed or slightly spreading, and the outer phyllaries are oblong-lanceolate in shape, while the inner are linear. The phyllaries have green chlorophyllous zones that are lanceolate to lance-rhombic with apices (tips) that have either short and sharp points (acute) or taper to long points (acuminate). Their margins appear white or light green, but they are actually translucent and may appear nibbled or worn away (in botanical terms, they are scarious and erose). They are inrolled and spinulose at the tips.[5]

Florets[edit]

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Close-up of flower head showing open and closed disk florets with elongated stamens, some with pollen still attached

Each flower head is made up of ray florets and disk florets. The 16 to 28[c] ray florets grow in one series and are usually white, rarely pinkish or bluish. They are usually between 5.4 and 7.5 mm (0.21 and 0.30 in) in length, but can be as short as 4 mm (0.16 in) and as long as 11 mm (0.43 in). They are 0.4 to 1.7 mm (0.016 to 0.067 in) wide[5] and they make up about 45% of the total number of florets on a flower head.[10]

The disks have 17 to 39[d] florets that start out as yellow and after opening, turn reddish purple or brown after pollination. Each disk floret is 3.4 to 4.1 mm (0.13 to 0.16 in) in depth (sometimes up to 5.5 mm (0.22 in)), and is made up of 5 petals, collectively a corolla, which open into 5 lanceolate lobes comprising 0.4 to 1 mm (0.02 to 0.04 in) of the depth of the floret.[5]

Fruit[edit]

The fruits of Symphyotrichum pilosum 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.[11] After pollination, they become off-white or gray with an oblong-obovoid shape, 1 to 1.5 mm (0.04 to 0.06 in) in length, and 0.5 to 0.7 mm (0.02 to 0.03 in) in width. They have 4 to 6 nerves and a few stiff, slender bristles on their surfaces (strigillose). Their pappi (tufts of hairs) are white and 3.5 to 4 mm (0.14 to 0.16 in) in length.[5] The seeds mature late in the season but cannot germinate at low temperatures. They are dispersed by the fall and winter winds and germinate when temperatures become warm in the spring.[6]

Chromosomes[edit]

S. pilosum has a monoploid number (also called base number) of eight chromosomes (x = 8).[12] There are plants of S. pilosum var. pilosum with four and six sets of the chromosomes, tetraploid with 32 total and hexaploid with 48 total, respectively. These cytotypes occur regularly, with occasional pentaploids (five sets) that have 40 in total. The involucre and floret sizes are different between the tetraploids and hexaploids,[13] and the latter are found primarily in formerly glaciated habitats.[14] S. pilosum var. pringlei is hexaploid with a total chromosome count of 48.[4]

Taxonomy[edit]

Etymology[edit]

The specific epithet[e] pilosum is from Latin pilosus meaning "with long soft hairs".[15] The species has the common names of hairy white oldfield aster,[16] frost aster, white heath aster, heath aster, hairy aster, common old field aster, old field aster, or steelweed.[17] Symphyotrichum pilosum var. pringlei is commonly known as Pringle's aster[4] and was named for American botanist Cyrus Guernsey Pringle.[7]

Varieties[edit]

Two varieties are accepted by Plants of the World Online (POWO).[2] S. pilosum var. pilosum, the autonym, has hairy stems and leaves. It is widespread and often weedy.[3] S. pilosum var. pringlei is hairless, or nearly so,[4] and grows in higher-quality calcium-rich ecosystems,[7] often with many companion flora.[18]

Classification[edit]

Symphyotrichum pilosum is classified in subgenus Symphyotrichum section Symphyotrichum subsection Porteriani. This subsection contains four species in addition to S. pilosum: S. depauperatum (serpentine aster), S. kentuckiense (Kentucky aster), S. parviceps (smallhead aster), and S. porteri (Porter's aster). Two commonalities among the five species are their revolute phyllaries and their summer- and fall-forming basal leaf rosettes.[12]

Subgenus Symphyotrichum cladogram
  • Symphyotrichum
    subg. Symphyotrichum
    sect. Conyzopsis[ref 2]: 271 
    sect. Occidentales[ref 2]: 271 
    sect. Turbinelli[ref 1]: 133 

    S. turbinellum

    sect. Symphyotrichum[ref 2]: 268 
    Cladogram references
    1. ^ a b c d e Semple, J.C.; Heard, S.B.; Brouillet, L. (2002). "Cultivated and Native Asters of Ontario (Compositae: Astereae)". University of Waterloo Biology Series. 41. Ontario: University of Waterloo: 1–134.
    2. ^ a b c d e Nesom, G.L. (September 1994). "Review of the Taxonomy of Aster sensu lato (Asteraceae: Astereae), Emphasizing the New World Species". Phytologia. 77 (3) (published 31 January 1995): 141–297. ISSN 0031-9430. Retrieved 23 August 2021 – via Biodiversity Heritage Library.

Distribution[edit]

Native[edit]

Both varieties of Symphyotrichum pilosum are native to central and eastern Canada and the United States, with the more common being S. pilosum var. pilosum.[3][4]

Variety pilosum[edit]

Sources differ slightly on the distribution of S. pilosum var. pilosum. According to Flora of North America (FNA), it is native from west starting in Minnesota, then east to Maine, including Ontario and Québec; south along the Atlantic Seaboard including most southern and eastern states; the entire Midwest; the states bordering the Mississippi River except Louisiana; then with a northwest border to Arkansas; and, four Great Plains states, from south to north, Oklahoma, Kansas, Nebraska, and South Dakota. States on the Atlantic Seaboard with no reported presence are Connecticut, Delaware, Maryland, Rhode Island, and Vermont, plus West Virginia. FNA reports that it has been introduced to the Canadian provinces of British Columbia, New Brunswick, and Nova Scotia.[3]

Plants of the World Online (POWO) and NatureServe provide slightly different distribution information on this variety. According to POWO, it also is present in and native to Maryland, New Brunswick, and Nova Scotia. Like FNA, however, POWO reports that it is an introduced species in British Columbia.[19] NatureServe's map for S. pilosum var. pilosum differs from FNA's with an additional introduced presence on Prince Edward Island; no presence in New Hampshire, Nebraska, or South Dakota; and, a presence in Connecticut, Delaware, Louisiana, Maryland, Rhode Island, and Washington, D.C.[20]

Variety pringlei[edit]

S. pilosum var. pringlei is an east-central and northeastern North American variety, and according to FNA and POWO, it is native to the area encompassing Minnesota in the northwest then east to Québec and Nova Scotia, in the United States on the Atlantic Seaboard south to North Carolina, then northwest to Kentucky, Illinois, and then north to Wisconsin.[4][21] NatureServe differs and includes a presence for this variety in Arkansas, Georgia, South Carolina, and Tennessee.[22]

Varietal native distributions by province and state
as reported in Flora of North America
  • Symphyotrichum pilosum var. pilosum native distribution map: Canada — Ontario, Quebec; United States — Alabama, Arkansas, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Maine, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Nebraska, New Hampshire, New Jersey, New York, North Carolina, Ohio, Oklahoma, Pennsylvania, South Carolina, South Dakota, Tennessee, Virginia, Wisconsin
    S. pilosum var. pilosum[3]
  • Canada – Nova Scotia, Ontario, and Quebec; United States – Connecticut, Delaware, District of Columbia, Illinois, Indiana, Kentucky, Maine, Maryland, Massachusetts, Michigan, Minnesota, New Hampshire, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, Vermont, Virginia, West Virginia, Wisconsin
    S. pilosum var. pringlei[4]

Introduced[edit]

S. pilosum var. pilosum is reported as an introduced species in the Canadian provinces of British Columbia, New Brunswick, Nova Scotia, and Prince Edward Island;[20] and, in the countries of Belgium, France, Germany, Great Britain, India, Italy, Korea, Netherlands, and Spain.[19] As of August 2022, it was not on the European Union's List of invasive alien species of Union concern.[23]

Habitat[edit]

Variety pilosum habitat[edit]

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S. p. var. pilosum growing in the sand near the man-made Blue Marsh Lake, Berks County, Pennsylvania, United States

S. pilosum var. pilosum is tolerant of harsh growing conditions.[18] It is is usually found at elevations between sea level and 1,000 meters (3,300 feet)[3] in disturbed areas such as fallowed land,[18] old fields, roadsides,[3] salted roadsides, railroads, pastures,[15] landfills, and quarries. It occurs less frequently[18] in natural prairies, open deciduous woods,[3] limestone outcrops,[24] and, very uncommonly, wetlands.[18]

It can be found among native flowering plants such as Solidago canadensis (Canada goldenrod), Solidago altissima (tall goldenrod),[25] Achillea millefolium (common yarrow), Asclepias syriaca (common milkweed), Erigeron annuus (daisy fleabane), Ambrosia artemisiifolia (common ragweed), and Ambrosia trifida (giant ragweed). It co-occurs with weedy introduced species, including Cirsium arvense (creeping thistle), Chenopodium album (lamb's quarters), Rumex crispus (curly dock), Daucus carota (Queen Anne's lace), Securigera varia (crownvetch), Lactuca serriola (prickly lettuce), Melilotus albus (white sweetclover), Melilotus officinalis (sweet yellow clover), and Pastinaca sativa (parsnip). Non-native grasses found with it include Bromus inermis (smooth bromegrass), Poa compressa (Canada bluegrass), Poa pratensis (Kentucky bluegrass), and Schedonorus arundinaceus (tall fescue).[15] On salted roadsides, it occurs with Symphyotrichum subulatum (eastern annual saltmarsh aster).[26]

Variety pringlei habitat[edit]

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S. pilosum var. pringlei at Rocky Ridge Natural Area, Rothrock State Forest, Huntingdon County, Pennsylvania, United States, which has exposures of limestone and Oriskany sandstone[27]

S. pilosum var. pringlei is common in calcium-rich ecosystems such as calcareous grasslands and fens,[7] limestone alvars,[28] shale outcrops,[18] and marly pannes.[f][7] It has also been found in various partially-sandy or sandy areas,[18] and on moraine cliffs along lakes in woodland openings, as well as in environments similar to these.[7] It can be found in habitats attractive to S. pilosum var. pilosum almost as equally as in the higher-quality ones previously mentioned.[18] Elevations of occurrences are from sea level to 1,100 meters (3,600 feet), sometimes higher.[4]

Pringle's aster has been found among 120 associate species in southwestern Ontario, with 13 to 45 individual species counted in different populations.[18] American botanist and lichenologist Gerould Wilhelm and American biologist Laura Rericha, in their 2017 Flora of the Chicago Region: a Floristic and Ecological Synthesis, list many companion flora. These depend upon the environment in which S. pilosum var. pringlei is growing.[7]

Hybridization[edit]

S. pilosum produces hybrids with other Symphyotrichum species that survive and reproduce beyond the first generation (beyond F1 hybridization). These surviving hybrid populations are called hybrid swarms. S. pilosum hybrids can interbreed with other hybrid individuals and backcross with their parent species. Its ability to do this has made S. pilosum valuable to the cut flower and cultivar industries.[29]

S. pilosum var. pilosum and the rare endemic Symphyotrichum kentuckiense[30] breed and produce an F1 hybrid that has been named Symphyotrichum × priceae.[31] The parent plants are both within subsection Porteriani[12] and have similar characteristics. However, S. kentuckiense is glabrous rather than pilose, and its flower heads are larger than those of S. pilosum, at about 25 mm (1 in) wide,[32] compared to those of S. pilosum, which are 13 to 19 mm (0.5 to 0.75 in) wide.[8] The heads of S. kentuckiense have blue,[33] blue-violet,[34] pink, or purple ray florets.[32] The hybrid is a somewhat hairy plant rather than a hairless one, and its characteristics are intermediate between its parents.[33]

Comparison of S. kentuckiense, S. × priceae, and S. pilosum var. pilosum
Part of an inflorescence of Symphyotrichum kentuckiense showing glabrous stem, many flower heads, and one in bloom with blue-violet ray florets
S. kentuckiense
Part of a Symphyotrichum × priceae plant showing puberulent stem and two flower heads, one opened and with blue-violet ray florets
S. × priceae
Part of an inflorescence of Symphyotrichum pilosum variety pilosum showing pubescent stems and several white flower heads
S. pilosum var. pilosum

Putative F1 hybrids of Symphyotrichum pilosum var. pilosum with twelve other species of the genus have been reported: S. cordifolium (common blue wood aster), S. drummondii (Drummond's aster), S. dumosum (bushy aster), S. laeve (smooth aster), S. lanceolatum (panicled aster), S. novi-belgii (New York aster), S. oolentangiense (skyblue aster),[29] S. parviceps (smallhead aster), S. praealtum (willowleaf aster), S. racemosum (small white aster),[35] S. tradescantii (shore aster), and S. urophyllum (arrowleaf aster).[29] Additionally, based on the discovery of pentaploids of S. pilosum var. pilosum, it has been determined that pollination has occurred between S. p. var. pilosum and S. p. var. pringlei or between the tetraploid and hexaploid cytotypes of S. p. var. pilosum.[36]

Conservation[edit]

NatureServe lists the species and its varieties with various conservation statuses, and some states and provinces within range do not have statuses. As of November 2022, S. pilosum was listed as Globally Secure (G5); and, State Secure (S5) in Ontario, Delaware, Georgia, Iowa, Mississippi, New York, North Carolina, Virginia, and West Virginia.[1]

S. pilosum var. pilosum was listed as a Globally Secure Variety (T5); Secure (S5) in Ontario, Delaware, Georgia, New Jersey, New York, Virginia, and West Virginia; and, Vulnerable (S3) in Québec and Minnesota.[20] S. pilosum var. pringlei also was listed as a Globally Secure Variety (T5); Secure (S5) in Delaware, New Jersey, and Virginia; Apparently Secure (S4) in Ontario and New York; Vulnerable (S3) in Minnesota; Imperiled (S2) in Québec and West Virginia; and, Critically Imperiled (S1) in Arkansas.[22] The global statuses were last reviewed in 2016.[1][20][22]

Cultivation[edit]

Symphyotrichum pilosum var. pringlei[37] and its cultivar 'Ochtendgloren'[38] have both won the Royal Horticultural Society's Award of Garden Merit.[39]

Notes[edit]

  1. ^ Sometimes as long as 50 mm (2 in)
  2. ^ See Asteraceae § Flowers for more detail.
  3. ^ Outside range about 10 to 38
  4. ^ Outside range about 13 to 67
  5. ^ Second part of the scientific name
  6. ^ Marl is "carbonate-rich mud or mudstone which contains variable amounts of clays and silt". (Copied definition from Marl; see that page's history for attribution.) A panne is a "wetland consisting of a small depression, with or without standing water". (Copied definition from the Wiktionary English noun ecology entry for panne; see that page's history for attribution.)

Citations[edit]

  1. ^ a b c NatureServe (2022).
  2. ^ a b c d POWO (2022).
  3. ^ a b c d e f g h i j k l Brouillet et al. (2006a).
  4. ^ a b c d e f g h i j k Brouillet et al. (2006b).
  5. ^ a b c d e f g h i j k l m n Brouillet et al. (2006).
  6. ^ a b Chmielewski & Semple (2001), p. 858.
  7. ^ a b c d e f g Wilhelm & Rericha (2017), p. 1105.
  8. ^ a b c NC State Extension (n.d.).
  9. ^ Morhardt & Morhardt (2004), p. 29.
  10. ^ Chmielewski & Semple (2001), p. 859.
  11. ^ Barkley, Brouillet & Strother (2006).
  12. ^ a b c Semple (2014c).
  13. ^ Semple (2014a).
  14. ^ Chmielewski & Semple (2001), p. 856.
  15. ^ a b c Wilhelm & Rericha (2017), p. 1104.
  16. ^ USDA (2014).
  17. ^ Chmielewski & Semple (2001), p. 851.
  18. ^ a b c d e f g h i Chmielewski & Semple (2001), p. 857.
  19. ^ a b POWO (2022a).
  20. ^ a b c d NatureServe (2022a).
  21. ^ POWO (2022b).
  22. ^ a b c NatureServe (2022b).
  23. ^ European Commission (2022).
  24. ^ Semple (2014).
  25. ^ Chmielewski & Semple (2001), p. 862.
  26. ^ Wilhelm & Rericha (2017), p. 1108.
  27. ^ DCNR (2022).
  28. ^ Semple (2014b).
  29. ^ a b c Chmielewski & Semple (2001), p. 860.
  30. ^ Weakley (2022).
  31. ^ POWO (2022i).
  32. ^ a b Britton (1901), p. 960.
  33. ^ a b Medley (2021), p. 2.
  34. ^ Brouillet et al. (2006d).
  35. ^ Yatskievych (2009).
  36. ^ Semple, Heard & Brouillet (2002), p. 84.
  37. ^ Royal Horticultural Society (n.d.a).
  38. ^ Royal Horticultural Society (n.d.b).
  39. ^ Royal Horticultural Society (2017).

References[edit]

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