Overview

Comprehensive Description

Comments

Downy Sunflower is an attractive plant, whether in or out of bloom. It can be readily distinguished from other sunflowers by the fine soft hairs that heavily cover both the leaves and stems; the broad clasping leaves; and the greater number of ray florets in the compound flowers. Return
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© John Hilty

Source: Illinois Wildflowers

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Description

This native perennial is 2-4' tall. It is unbranched, except for a few small flowering stems near the top of the plant. The stout central stem is covered with fine hairs. The opposite leaves are up to 4" long and 2½" across. They are broadly lanceolate, and either clasp the stem or are sessile. Fine soft hairs cover both the lower and upper sides of the leaves, which are greyish green or bluish green. Their margins are smooth, or have small blunt teeth. The composite flowers develop singly from upper stems, and span about 2½–4" across. A composite flower consists of numerous yellow disk florets, and 15-30 surrounding yellow ray florets. The central disk of a composite flower is initially brown because of the bracts of the disk florets, but it later turns yellow. The blooming period occurs from late summer to early fall, and lasts about 1-2 months. There is little scent to the flowers. The dark seeds have a shiny surface, but no tufts of hair. The root system is fibrous and rhizomatous. This plant tends to form dense colonies, in part because the root system exudes allelopathic chemicals that inhibit the growth of other species of plants. Cultivation
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© John Hilty

Source: Illinois Wildflowers

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Distribution

Range and Habitat in Illinois

Downy Sunflower occurs occasionally in the southern half of Illinois, as well as NE Illinois; it is rare or absent elsewhere, especially in NW Illinois (see Distribution Map). Habitats include mesic to dry black soil prairies, sand prairies, clay prairies, thickets, barrens with sparse vegetation, rocky glades, abandoned fields, and areas along roadsides and railroads. This plant tends to occur in high quality habitats. Faunal Associations
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© John Hilty

Source: Illinois Wildflowers

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National Distribution

Canada

Origin: Exotic

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

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Physical Description

Morphology

Description

Perennials, 50–150+ cm (rhizoma-tous). Stems erect, hirsute to villous. Leaves mostly cauline; mostly opposite (sometimes alternate among heads); sessile; blades (ashy or gray-green, 3-nerved distal to bases) lance-olate to broadly ovate, 5.5–14.5 × 1.8–6.5 cm, bases rounded to cordate, margins entire or serrulate, abaxial faces hispid to tomentose, gland-dotted. Heads 1–15. Peduncles 0.1–15 cm. Involucres broadly hemispheric, 12–25 mm diam. Phyllaries 30–40, lanceolate, (5–)10–16 × 2–3.5 mm, apices usually acute, sometimes acuminate, abaxial faces densely hispid to villous or tomentose, densely gland-dotted. Paleae (oblanceolate) 9–11 mm, entire (1-toothed, densely hairy, densely gland-dotted). Ray florets 17–22; laminae 25–30 mm (abaxial faces densely gland-dotted). Disc florets 75+; corollas 6–7.5 mm, lobes yellow; anthers dark, appendages dark. Cypselae 3.5–4 mm, distally villous; pappi of 2 aristate scales 2.8–3.2 mm. 2n = 34.
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Diagnostic Description

Synonym

Helianthus mollis var. cordatus S. Watson
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Ecology

Habitat

Range and Habitat in Illinois

Downy Sunflower occurs occasionally in the southern half of Illinois, as well as NE Illinois; it is rare or absent elsewhere, especially in NW Illinois (see Distribution Map). Habitats include mesic to dry black soil prairies, sand prairies, clay prairies, thickets, barrens with sparse vegetation, rocky glades, abandoned fields, and areas along roadsides and railroads. This plant tends to occur in high quality habitats. Faunal Associations
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Source: Illinois Wildflowers

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Associations

Flower-Visiting Insects of Downy Sunflower in Illinois

Helianthus mollis (Downy Sunflower)
(Bees collect pollen or suck nectar, other insects suck nectar; most observations are from Robertson, otherwise they are from Moure & Hurd, Hilty, and Krombein et al. as indicated below)

Bees (long-tongued)
Apidae (Bombini): Bombus pensylvanica sn fq; Anthophoridae (Epeolini): Triepeolus concavus sn, Triepeolus cressonii cressonii sn; Anthophoridae (Eucerini): Melissodes agilis sn cp olg, Melissodes coloradensis sn, Melissodes trinodis sn cp, Svastra obliqua obliqua sn cp fq; Megachilidae (Coelioxini): Coelioxys octodentata sn; Megachilidae (Megachilini): Megachile brevis brevis sn, Megachile latimanus sn cp, Megachile parallela parallela sn, Megachile petulans sn

Bees (short-tongued)
Halictidae (Halictinae): Agapostemon virescens sn, Augochlorella aurata sn cp, Augochloropsis metallica metallica (MH), Halictus ligatus sn cp fq, Lasioglossum pilosus pilosus sn cp, Lasioglossum versatus sn cp; Andrenidae (Panurginae): Heterosarus albitarsis sn cp icp, Pseudopanurgus rugosus sn cp olg (Rb, Kr)

Flies
Syrphidae: Eristalis stipator sn, Tropidia mamillata sn; Bombyliidae: Exoprosopa decora sn, Poeciloanthrax alcyon sn, Systoechus vulgaris sn fq

Butterflies
Nymphalidae: Danaus plexippus (H), Phyciodes tharos; Pieridae: Colias philodice

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Helianthus mollis

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 1
Species With Barcodes: 1
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Source: Barcode of Life Data Systems (BOLD)

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Conservation

Conservation Status

National NatureServe Conservation Status

Canada

Rounded National Status Rank: NNA - Not Applicable

United States

Rounded National Status Rank: N4 - Apparently Secure

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NatureServe Conservation Status

Rounded Global Status Rank: G4 - Apparently Secure

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Notes

Comments

Helianthus mollis is introduced in Ontario and adventive in the eastern United States (e.g., Maine), where it is continuing to spread, particularly along roads. Natural hybrids between H. mollis and H. occidentalis have been named H. cinereus Torrey & A. Gray (R. C. Jackson and A. T. Guard 1957); they differ from H. mollis by having smaller heads with fewer ray florets and narrower leaves with cuneate bases. Hybrids of H. mollis with H. giganteus have been called H. doronicoides Lamarck (Jackson 1956).
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