Overview

Comprehensive Description

Description

This native perennial wildflower is 3-5' tall. The erect stems are unbranched, except in the upper-third of each plant. Each stem is light green, glabrous, 4-angled, and slightly winged on the angles. The opposite leaves are up to 4" long and 1½" across; they are lanceolate, lanceolate-ovate, or ovate, smooth along the their margins, and glabrous. The upper surface of each leaf is medium green, while the lower surface is pale green. The leaves are sessile or they clasp the stem slightly. The central stem and lateral upper stems (if any) terminate in cymes of 1-5 flowers. Relative to the size of the flowers, branches of each cyme are rather short. Each flower is about 2" across, consisting of 5 yellow petals, 5 green sepals, numerous yellow stamens (about 100), and a light green pistil with 5 persistent styles. The petals are widely spreading and often rather floppy or contorted; they may develop streaks of white with age. The sepals are lanceolate-ovate and much shorter than the petals. The blooming period occurs during mid-summer and lasts about 2-3 weeks. Each flower is replaced by a large hairless seed capsule up to 1¼" long and ½" across. Each seed capsule is divided into 5 cells; each cell contains numerous small seeds that are narrowly oblongoid, flattened, and black at maturity. The root system is rhizomatous, often forming small colonies of plants.
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Distribution

Range and Habitat in Illinois

Giant St. John's Wort is occasional in northern and west-central Illinois; it is rare or absent elsewhere in the state. Illinois lies along the southern range limit of this species in North America; it also occurs in Eurasia. Habitats are rather variable, but they include woodland openings, wooded slopes, banks of rivers and streams, moist thickets and meadows, river-bottom prairies, and fens. This species is usually found in high quality habitats. It is sometimes cultivated in gardens.
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National Distribution

Canada

Origin: Unknown/Undetermined

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

United States

Origin: Unknown/Undetermined

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

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Global Range: QUEBEC, ONTARIO, AND POSS. MANITOBA S TO KANSAS, MISSOURI, I LL., IND, OH, PA, MD, AND NJ. THE PLANT IS SPORATIC AND RAR E IN ALL THE NE STATES. IT HAS BEEN SUGGESTED THAT THIS SPO RATIC DISTRIBUTION COINSIDES WITH PAST IDIAN CAMP SITES.

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Throughout China except Xizang [Japan, Korea, Mongolia, Russia (Altai to Kamchatka and Kurile Islands, Sakhalin), Vietnam; North America (E Canada, NE United States)].
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Physical Description

Morphology

Description

Herbs, perennial, 0.5-1.3(-2) m tall, erect or sometimes ascending from short creeping base; stems single or few, cespitose, unbranched or branched above or nearly throughout. Stems 4-angled when young, becoming 4-lined or occasionally internodes 2-lined below. Leaves sessile; blade lanceolate or ± narrowly ovate or oblong or elliptic to oblong-linear or oblanceolate, (3-)4-9.7(-12) × (0.4-)0.7-3.5(-4) cm, thickly papery, abaxially rather paler but not glaucous; laminar glands dense, unequal dots or short streaks; intramarginal glands dense; main lateral veins 4-7-paired, tertiary reticulation dense, often obscure; base cuneate to cordate-amplexicaul, apex acute to subapiculate or obtuse (or lowermost rarely rounded). Inflorescence 1- to ca. 35-flowered from 1-5 nodes, the whole nearly flat-topped to narrowly pyramidal, sometimes with flowering branches from up to 4 nodes below; bracts and bracteoles leaflike but smaller and often broader, more rarely linear-lanceolate and deciduous. Flowers 3-7(-8) cm in diam., stellate with petals spreading to reflexed; buds broadly to narrowly ovoid, apex rounded to subacute. Sepals free, erect, oblong to elliptic or ovate to ovate-lanceolate or obovate, subequal to unequal, the outer ones sometimes leaflike, (0.3-)0.5-1.5 cm × (1.5-)2-7(-10) mm; laminar glands lines, distally interrupted to streaks; marginal glands spaced, small, margin entire, apex rounded to obtuse or rarely subacuminate to acute; veins 11-17. Petals bright (to ?golden) yellow, sometimes tinged red in bud, obovate or oblong-obovate to oblanceolate, often somewhat spatulate to subunguiculate, strongly curved to nearly straight, 1.4-4.1 × 0.5-2 cm, 2-3 × as long as sepals or shorter when sepals leaflike; laminar glands lines to short streaks; marginal glands absent; margin entire, apex rounded or obtuse to rarely acute to acuminate; apiculus short and rounded or absent. Stamen fascicles (?4 or)5, each with ca. 30 stamens, longest 0.9-2.5 cm, 0.4-0.67 × as long as petals. Ovary broadly ovoid to narrowly ovoid-pyramidal or ellipsoid; styles (4 or)5, 2.5-15 mm, 0.5-2 × as long as ovary, free or up to 0.8 coherent or connate; stigmas broadly capitate to funnel-shaped. Capsule broadly to narrowly ovoid or ovoid-pyramidal or rarely narrowly cylindric, 0.9-2.2(-3) cm × 5-13 mm, 2-3 × as long as sepals, apex obtuse to rounded. Seeds dark red-brown to yellow-brown, 1-1.5 mm, deeply carinate or narrowly winged, sometimes with slight terminal expansion; testa densely shallowly linear-reticulate. Fl. Jun-Sep, fr. Aug-Oct. 2n = 16, 18, 20, 22 (usually 18).
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Ecology

Habitat

Range and Habitat in Illinois

Giant St. John's Wort is occasional in northern and west-central Illinois; it is rare or absent elsewhere in the state. Illinois lies along the southern range limit of this species in North America; it also occurs in Eurasia. Habitats are rather variable, but they include woodland openings, wooded slopes, banks of rivers and streams, moist thickets and meadows, river-bottom prairies, and fens. This species is usually found in high quality habitats. It is sometimes cultivated in gardens.
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Comments: USUALLY ALLUVIAL SOILS (RIVER-MEADOWS, COBBLE SHORES) IN MID WEST ALSO IN MESIC PRARIES, MESIC FORESTS EDGES, POST OAK WD

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Moist to dry meadows, grassy or rocky slopes, sometimes in forests or among scrub, streamsides and river banks; sea level to 2800(-3600) m.
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Associations

Faunal Associations

The flowers are pollinated primarily by bumblebees, which collect pollen. Smaller bees and other insects may visit the flowers as well, but they are less effective pollinators. Only pollen is available as a reward to floral visitors. Some insects feed on the leaves, flowers, and other parts of this and other Hypericum spp. (St. John's Wort species). These include the caterpillars of the moths Eupithecia miserulata (Common Pug), Melanchra assimilis (Black Arches), Synchlora aerata (Wavy-Lined Emerald), Hyppa xylinodes (Common Hyppa), Nedra ramosula (Gray Half-Spot), and Agonopterix hyperella (Oecophorid Moth sp.). The caterpillars of the butterfly Strymon melinus (Gray Hairstreak) feed on the developing capsules and seeds. Other insects that feed on Hypericum spp. include the aphid Brachysiphum hyperici, and the leaf beetles Pachybrachis relictus and Paria sellata. The foliage is somewhat toxic to mammalian herbivores and usually avoided because it can cause irritation of the gastrointestinal tract. The foliage can also cause a harmful reaction to sunlight in light-skinned animals (e.g., pigs), causing irritation of the skin.
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Flower-Visiting Insects of Great St. John's Wort in Illinois

Hypericum pyramidatum (Great St. John's Wort)
(Bees collect pollen only; observations are from Robertson)

Bees (long-tongued)
Apidae (Bombini): Bombus pensylvanica, Bombus vagans

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Population Biology

Number of Occurrences

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

Comments: PROBABLY MORE THAN 200 EO'S, MOST IN MIDWEST

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Hypericum ascyron

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 5
Species With Barcodes: 1
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Conservation

Conservation Status

National NatureServe Conservation Status

Canada

Rounded National Status Rank: NNR - Unranked

United States

Rounded National Status Rank: NNR - Unranked

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NatureServe Conservation Status

Rounded Global Status Rank: G4 - Apparently Secure

Reasons: APPARENTLY SECURE IN OH, MI, IL, AND MN

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Threats

Comments: POSSIBLE LOSS OF HABITAT DUE TO DAMS IN E RANGE.

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Management

Biological Research Needs: TRY TO EVALUATE WHETHER E EO'S WERE INDRODUCED BY INDIANS

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Relevance to Humans and Ecosystems

Benefits

Cultivation

The preference is full sun to light shade and moist conditions. This wildflower adapts to different kinds of soil, including loam, clay-loam, and rocky soil. It is robust and easy to grow.
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Notes

Comments

Hypericum ascyron is a highly variable species or species complex with a very wide distribution. Although several variants have been recognized as varieties or even species, the variation appears to be nearly continuous.

The most frequently distinguished taxon has been Hypericum gebleri, which most Russian authors have recognized, as it occurs throughout most of S Siberia along with larger-flowered, less-branched forms and is present alone in Kamchatka, the Kurile Islands, and Sakhalin. On the other hand, Chinese authors have tended to include it in H. ascyron, because intermediate forms occur in the north. The North American population, too, was recognized early at species level but none of the characters said to distinguish it appears to be constant.

Under these circumstances, it seems best to distinguish the N Asian Hypericum gebleri and the North American H. pyramidatum Aiton as subspecies (see Robson, Bull. Nat. Hist. Mus. Lond. (Bot.) 31: 37-88. 2001). It seems impossible to recognize the long-styled (mainly large-flowered and northern) plants and the narrow-fruited, C Chinese ones (respectively var. longistylum and var. giraldii [var. hupehense]) as distinct taxa, as both represent extremes of continuous variation. Likewise, the narrow-leaved, small-flowered form from S China (misidentified as var. angustifolium Y. Kimura) merges with more typical forms.

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Names and Taxonomy

Taxonomy

Comments: Robson (2001) regards North American plants as a subspecies of Hypericum ascyron.

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