Brown-Eyed Susan can be distinguished from similar species by the smaller size of its flowerheads and the smaller number of ray florets per flowerhead. It is usually more tall and bushy than Rudbeckia hirta (Black-Eyed Susan), but it is shorter with fewer lobed leaves than Rudbeckia laciniata (Cutleaf Coneflower). Brown-Eyed Susan is often observed in the eastern range of the tallgrass prairie, but it tends to retreat to wetland or woodland areas further to the west where rainfall amounts are lower and summer temperatures are more extreme. Return

This is a biennial or short-lived perennial plant up to 5' tall. It branches frequently at the leaf axils and its appearance is rather bushy at maturity. The stems are dark red and they have conspicuous white hairs, particularly along the upper half of the plant. The alternate leaves are up to 4' long and 2' across. They are lanceolate to ovate, slightly to coarsely dentate, and rough-textured from minute stiff hairs. Some of the lower leaves are divided into three lobes. Individual upper stems terminate in 1-2 flowerheads. Each flowerhead is about 1½-2' across, consisting of 6-12 ray florets that surround a brown to black flattened cone of numerous disk florets. The petaloid rays of the flowerheads are bright yellow and oblong in shape. The tiny disk florets are narrowly cylindrical. Around the base of each flowerhead, there are inner and outer floral bracts (phyllaries) that are green and ciliate. The flowerheads have little or no scent. The blooming period occurs from mid-summer to late summer for about 1-2 months. On robust plants, 6 or more flowerheads are often in bloom at the same time, creating a showy effect. The small achenes are 4-angled and have no tufts of hair. The root system is shallow and fibrous. Cultivation

Linnaeus first descriped Rudbeckia triloba in Species Plantarum in 1753. John Torrey and Asa Gray introduced the variety pinnatiloba in 1841 in A Flora of North America: Containing Bridged Descriptions of all the known Indigenous and Naturalized plants growing North of Mexico arranged according to the Natural System. Only 3 years later, Asa Gray published Synoptical Flora of North America, including the three modern varieties, pinnatiloba, rupestris and triloba.

The native Brown-Eyed Susan is a common plant in Illinois, except for some counties in the southern and NW sections of the state (see Distribution Map). Habitats include black soil prairies, prairie remnants along railroads, thickets, savannas, meadows and openings in wooded areas, riverbanks, edges of fens, roadsides, vacant lots, and abandoned fields. Areas with a history of disturbance are preferred, although this plant also occurs in high quality natural areas.

Rudbeckia triloba L.:
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Rudbeckia triloba is located throughout the eastern United States and up into southeastern Canada, into the central plains and some desert states. Var. pinnatiloba is confined to Virginia, North Carolina, Kentucky, Tennessee, Alabama and Florida. Var. rupestris grows only in North Carolina, Tennessee, Kentucky and Iowa. Var. triloba spans the entire species' range, excluding Florida. (Urbatsch & Cox, 2006.)

For more information, see the map provided by Flora of North America.

Canada

Origin: Exotic

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Key taken from Flora of North America. (Urbatsch & Cox, 2006.)

1. Cauline leaves (at least some) 5-7 lobed (Florida, Kentucky, North Carolina, Virginia………

……………………........................................................23a. Rudbeckia triloba var. pinnatiloba

1. Cauline leaves (at least some) 3-lobed.

2. Ray laminae 8-17 mm; discs 10-15 mm diam. (20-100 m; relatively widespread)………

.....................................................................…………….23c. Rudbeckia triloba var. triloba

2. Ray laminae 18-30 mm; discs 15-20 mm diam. (100-1200 m; Iowa, Kentucky, North

Carolina, Tennessee)…………………………………23b. Rudbeckia triloba var. rupestris

Perennials, to 150 cm (rhizomatous). Stems glabrate to hirsute or strigose (hairs 1–2 mm, basal retrorse, others spreading). Leaves: blades ovate to subcordate or elliptic (not lobed), margins serrate, apices acute to acuminate, faces hirsute to strigose; basal petiolate, 10–30 × 2–8 cm, bases truncate or rounded to cordate; cauline petiolate or sessile, ovate to elliptic, proximal usually 3–5-lobed, 2–20 × 1.5–8 cm (smaller, fewer lobed distally), bases rounded to attenuate, sometimes clasping. Heads (10–30) in paniculiform arrays. Phyllaries to 1.5 cm (faces moderately hirsute). Receptacles conic to subhemispheric; paleae 5–6.5 mm, apices cuspidate (tips awnlike, 1.5+ mm), glabrous. Ray florets 8–15; laminae (corollas yellow to yellow-orange with basal maroon splotches) linear to oblanceolate, 8–30 × 3–8 mm, abaxially sparsely strigose. Discs 8–15 × 10–20 mm. Disc florets 150–300+; corollas yellowish green basally, otherwise brown-purple, 3–4 mm; style branches ca. 1.2 mm, apices obtuse to rounded. Cypselae 1.9–2.8 mm; pappi coroniform, to 0.2 mm.

"Perennials, to 150 cm (rhizomatous). Stems glabrate to hirsute or strigose (hairs 1–2 mm, basal retrorse, others spreading). Leaves: blades ovate to subcordate or elliptic (not lobed), margins serrate, apices acute to acuminate, faces hirsute to strigose; basal petiolate, 10–30 × 2–8 cm, bases truncate or rounded to cordate; cauline petiolate or sessile, ovate to elliptic, proximal usually 3–5-lobed, 2–20 × 1.5–8 cm (smaller, fewer lobed distally), bases rounded to attenuate, sometimes clasping. Heads (10–30) in paniculiform arrays. Phyllaries to 1.5 cm (faces moderately hirsute). Receptacles conic to subhemispheric; paleae 5–6.5 mm, apices cuspidate (tips awnlike, 1.5+ mm), glabrous. Ray florets 8–15; laminae (corollas yellow to yellow-orange with basal maroon splotches) linear to oblanceolate, 8–30 × 3–8 mm, abaxially sparsely strigose. Discs 8–15 × 10–20 mm. Disc florets 150–300+; corollas yellowish green basally, otherwise brown-purple, 3–4 mm; style branches ca. 1.2 mm, apices obtuse to rounded. Cypselae 1.9–2.8 mm; pappi coroniform, to 0.2 mm."

Urbatsch, Lowell E. and Patricia B. Cox. “Rudbeckia” in Flora of North America, Vol. 21, p. 59 Oxford University Press, Inc., New York, NY. 2006.

The native Brown-Eyed Susan is a common plant in Illinois, except for some counties in the southern and NW sections of the state (see Distribution Map). Habitats include black soil prairies, prairie remnants along railroads, thickets, savannas, meadows and openings in wooded areas, riverbanks, edges of fens, roadsides, vacant lots, and abandoned fields. Areas with a history of disturbance are preferred, although this plant also occurs in high quality natural areas.

Vars. pinnatiloba and rupestris grow strictly in mesic wetlands, but var. triloba has also been found in roadside meadows, pastures and thickets.

Autotroph

Brown-Eyed Susan is often self-pollinated, but it nonetheless attracts numerous nectar-seeking and pollen-seeking insects to its flowers. These visitors include bumblebees, little carpenter bees (Ceratina spp.), digger bees (Melissodes spp.), cuckoo bees (Triepeolus spp., Coelioxys spp.), leaf-cutting bees (Megachile spp.),  Andrenid bees (Andrena spp., Heterosarus spp.), and Halictid bees (including green metallic bees). One of these bees, Andrena rudbeckiae, is a specialist pollinator (oligolege) of Rudbeckia and Ratibida coneflowers. Other floral visitors include Sphecid wasps, Vespid wasps, Syrphid flies, bee flies, thick-headed flies, Tachinid flies, small to medium-sized butterflies, and the common Chauliognathus pennsylvanicus (Goldenrod Soldier Beetle). Other insects feed destructively on Brown-Eyed Susan and other Rudbeckia spp. These insects include the leaf beetles Brachypnoea clypealis and Sumitrosis inaequalis, the aphids Uroleucon ambrosiae and Uroleucon rudbeckiae, and caterpillars of the Tortricid moths Epiblema carolinana (feeding on roots), Epiblema tandana (feeding on roots), and Epiblema triparitana (feeding on flowerheads & stems). The foliage is sometimes browsed by deer, rabbits, groundhogs, and other mammalian herbivores.

Rudbeckia triloba (Brown-Eyed Susan)
(Bees collect pollen or suck nectar; beetles feed on nectar or pollen; flies mostly suck nectar; other insects suck nectar; most observations are from Robertson, although a few observations are from Moure & Hurd, Krombein et al., and MacRae as indicated below)

Bees (long-tongued)
Apidae (Apinae): Apis mellifera sn cp; Apidae (Bombini): Bombus auricomus sn, Bombus fraternus sn, Bombus griseocallis sn fq; Anthophoridae (Ceratinini): Ceratina dupla dupla sn cp fq; Anthophoridae (Epeolini): Triepeolus cressonii cressonii sn fq, Triepeolus helianthi helianthi sn, Triepeolus lunatus concolor sn; Anthophoridae (Eucerini): Melissodes agilis sn fq, Melissodes bimaculata bimaculata sn, Melissodes boltoniae cp, Melissodes denticulata sn, Melissodes rustica sn, Melissodes trinodis sn cp fq, Svastra obliqua obliqua sn cp fq; Megachilidae (Coelioxini): Coelioxys alternata alternata sn, Coelioxys octodentata sn, Coelioxys sayi sn; Megachilidae (Megachilini): Megachile brevis brevis sn, Megachile inimica sayi sn cp, Megachile petulans sn; Megachilidae (Stelidini): Stelis trypetinum sn; Megachilidae (Trypetini): Heriades leavitti sn

Bees (short-tongued)
Halictidae (Halictinae): Agapostemon sericea sn, Augochlora purus purus sn cp, Augochlorella aurata sn cp, Augochlorella striata sn cp, Halictus confusus sn, Halictus ligatus sn cp fq, Halictus rubicunda sn, Lasioglossum coriaceus sn, Lasioglossum imitatus sn cp, Lasioglossum pectoralis sn cp fq, Lasioglossum pilosus pilosus sn cp fq, Lasioglossum versatus sn cp, Lasioglossum zephyrus sn; Halictidae (Nomiinae): Nomia triangulifera (MH, Kr); Colletidae (Colletinae): Colletes americana sn cp, Colletes compactus sn cp; Andrenidae (Andreninae): Andrena aliciae sn cp fq, Andrena rudbeckiae sn cp olg (Rb, Kr); Andrenidae (Panurginae): Calliopsis andreniformis sn, Calliopsis coloradensis sn cp, Heterosarus andrenoides sn cp, Heterosarus compositarum sn, Heterosarus labrosiformis labrosiformis sn cp, Heterosarus labrosus sn cp fq, Heterosarus rudbeckiae sn cp fq icp olg, Pseudopanurgus rugosus sn cp (Rb, Kr)

Wasps
Sphecidae (Bembicinae): Bembix americana, Bicyrtes ventralis, Glenostictia pictifrons; Sphecidae (Crabroninae): Oxybelus emarginatus; Sphecidae (Sphecinae): Ammophila nigricans, Eremnophila aureonotata; Vespidae: Polistes fuscata; Vespidae (Eumeninae): Euodynerus annulatus; Sapygidae: Sapyga interrupta; Tiphiidae: Myzinum quinquecincta; Ichneumonidae: Exetastes suaveolens

Flies
Syrphidae: Copestylum vittatum sn, Eristalis stipator sn, Eristalis transversus sn fq, Mallota bautias sn, Spilomyia longicornis sn; Empidae: Empis clausa sn fq; Bombyliidae: Anthrax oedipus fp np, Chrysanthrax cypris sn, Exoprosopa decora sn, Exoprosopa fasciata sn, Exoprosopa fascipennis sn, Lepidophora lepidocera sn, Poecilanthrax alcyon sn fq, Pthiria cincta sn (Coquillett, MS), Sparnopolius confusus sn fq, Systoechus vulgaris sn, Systropus macer sn, Toxophora amphitea sn; Conopidae: Physoconops brachyrhynchus sn, Thecophora occidensis sn, Zodion obliquefasciatum sn; Tachinidae: Archytas analis sn, Clausicella geniculata sn fq, Copecrypta ruficauda sn, Cylindromyia euchenor sn, Epigrimyia illinoensis sn, Estheria abdominalis sn, Gymnoclytia occidua sn, Leskiomima secunda sn (Rb, MS), Periscepsia laevigata sn, Plagiomima spinosula sn fq, Spallanzania hesperidarum sn, Tachinomyia panaetius sn fq; Sarcophagidae: Sphixapata trilineata sn; Muscidae: Neomyia cornicina sn; Milichiidae: Eusiphona mira sn

Butterflies
Nymphalidae: Chlosyne nycteis fq, Limenitis archippus, Phyciodes tharos fq; Lycaenidae: Everes comyntas; Pieridae: Colias philodice, Pontia protodice

Skippers
Hesperiidae: Polites peckius

Beetles
Buprestidae: Acmaeodera pulchella (McR); Cantharidae: Chauliognathus pennsylvanicus sn fq; Meloidae: Epicauta pensylvanica fp np; Mordellidae: Mordella marginata fp np

Attempts at hybridization with R. triloba have been unsuccessful. Insect associations include a number of bees and flies, and some wasps, beetles and butterflies.

Aphids, powdery mildew

Rudbeckia triloba is a preferred source of nectar to a variety of flying insects.

All varieties flower summer to fall.

Perennial

Usually three to several years

Generally sexual, although some polyploids are apomictic.

R. triloba grows at a medium rate.

Var. triloba contains coumarin and two other closely related thiopheneacetylenes. (Gutierrez & Herz, 1990.)

Ray florets of Rudbeckia triloba still contain vestigial stamens. Some corollas in the same head may be three-lobed and five-lobed. (Koch, 1930.)

Rudbeckia triloba has a chromosome number of n=19. (Jones, 1970.)

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 4
Species With Barcodes: 1

Rudbeckia triloba has been classified as an endangered species in the state of Florida. (USDA, 2010.)

Rounded Global Status Rank: G5 - Secure

Canada

Rounded National Status Rank: NNA - Not Applicable

United States

Rounded National Status Rank: N4 - Apparently Secure

Rudbeckia triloba is covered in Tennessee under the Rare Plant Protection and Conservation Act of 1985, T.C.A. Section 70-8-301 et seq.

Rudbeckia triloba is commonly cultivated in flower and butterfly gardens. Like other species of Rudbeckia, its various parts have been used in diuretic teas, as anti-inflammatory agents and as painkillers. (Moerman, 1998.) The chemical compound Coumarin is naturally transformed into an anticoagulant by a series of reactions with fungi, and is then used in pharmaceutical anticoagulants like Coumadin. (Gutierrez & Herz, 1990.)