A genus of perennials that are part of the larger Daisy family. These make stunning plants for a focal point or the back of the landscape border. They are long lived, lasting decades but are slow to establish developing a huge taproot before much growth above ground.
They thrive in full sun and are very clay and drought tolerant. They are propagated from seed though division is possible with care while dormant. They are usually both deer and rabbit resistant.
* photos taken @ U.S. Botanical Garden, Wash., DC on Aug 25 2014
* photos taken on July 24 2021 in Columbia, MD
Silphium albiflorum ( White Rosinweed )
A slow growing but very long-lived, very deep taprooted ( up to 15 feet deep ), bushy perennial, reaching up to 2.5 feet, that is native to prairies in central Texas.
The stunning, very densely white-haired, deeply-cut foliage is silvery-gray. The foliage is 1 to 2 pinnately-lobed.
The showy, white flowers are borne late spring to mid-summer.
Hardy zones 7 to 8b in full sun on sandy or gravelly, well drained soil. It is extremely heat and drought tolerant and also tolerates alkaline soil. It has medium deer resistance.
* photo taken @ U.S. Botanical Garden, Wash., DC on Aug 25 2014
* photos taken by Clarence A. Rechenthin @ USDA-NRCS PLANTS Database
Silphium asteriscus ( Starry Rosinweed )
A perennial, reaching up to 6 x 2 feet, that is native to dry meadows and open woods in the southeastern U.S. ( from Oklahoma to southern Illinois to southern Maryland; south to eastern Texas to northern Florida ). It is endangered in Maryland and also Virginia where it is only found in Shenandoah County. Subspecies 'Trifoliatum' ( Whorled Rosin-Weed ) was known to occur around Amherstburg during the 1800s. It has not been seen there recently.
The coarsely-toothed, ovate leaves, up to 6 x 1.6 inches in size, are mid-green. The basal leaves are semi-evergreen.
The bright yellow flowers are borne early summer to mid-autumn.
Hardy zones 5 to 9 in full sun to partial shade. Very drought tolerant.
* photo taken on July 10 2024 @ Brookside Gardens, Wheaton, MD
Silphium glutinosum ( Sticky Rosinweed )
A fibrous rooted perennial, reaching up to 6 feet in height, with a tiny native of range of just one single county ( Bibb County in central Alabama ) worldwide. It is found on limestone outcrops in the wild. Endangered in the wild, it makes a spectacular landscape plant and should be nursery propagated for this purpose.
The oppositely-arranged, smooth-edged, oval to triangular leaves, up to 9 x 5 inches in size, are deep green.
The yellow flowers are borne early summer to early autumn.
Hardy zones 6 to 8 ( estimate ) in full sun on alkaline, well drained soil.
* photos taken @ U.S. Botanical Garden, Wash., DC on Aug 25 2014
Silphium gracile ( Slender Rosinweed )
A rhizomatous perennial, reaching up to 8 x 5 ( rarely over 5 x 3.3 ) feet in height, that is native to prairies and longleaf pine flatlands from Corpus-Christi, Texas to far northern Louisiana to central Alabama; south to the Gulf Coast. It is endangered in the wild, extinct in Georgia and Florida.
The oppositely-arranged, oval leaves are mid-green. The bright yellow flowers, up to 3 inches wide, are borne late summer to early autumn.
Hardy zones 7 to 9b ( reports of 5 & 6 ) in full sun to partial shade on acidic, sandy, well drained soil. While preferring moist soil, it is moderately heat tolerant and very heat tolerant. They can be cut back during early summer for a shorter, denser plant at bloom time. It is easily propagated from seed, less easily by carefully dividing the rhizomes while dormant.
* photos taken @ U.S. Botanical Garden, Wash., DC on Aug 25 2014
* photos taken on Aug 24 2017 @ U.S. Botanic Garden, Wash. DC.
* photo taken by Clarence A. Rechenthin @ USDA-NRCS PLANTS Database
Silphium integrifolium ( Wholeleaf Rosinweed )
A moderate growing, rhizomatous perennial, reaching up to 8 x 4 ( rarely over 6 x 3 ) feet, that is native to prairies in central and eastern U.S. ( from southeast South Dakota to southern Ontario; south to New Mexico to Alabama ). It is extremely rare and local in much of its natural range. It is extinct in Colorado. Critically endangered in Wyoming, South Dakota and Michigan.
The long pointed leaves are stemless. The mid-green foliage often turns to yellow during autumn.
It bears large yellow flowers, up to 3 inches across, are borne on terminal clusters over a long season of up to 2 months from mid summer to early autumn.
Hardy zones 4 to 8 in full sun to partial shade on well drained soil including clay. Salt tolerant.
* photos taken on Aug 4 2013 in Bayfield, Ontario
* photos taken on July 13 2021 @ Hershey Gardens, Hershey, PA
* photos taken on Sep 3 2024 in Columbia, MD
Silphium laciniatum ( Compass Plant )
A moderate growing, clumping perennial, reaching a maximum size of 14 x 4 ( rarely over 10 ) feet, that is native to prairies of central North America ( from far southwest Nebraska to northeast South Dakota to central Wisconsin to southern Michigan to St Thomas, Ontario & northern Ohio; south central Texas to central Alabama ). It is critically endangered in Ontario, Michigan, Ohio, Kentucky and Tennessee. It was also threatened in South Dakota. It was abundant in Detroit, Michigan during presettlement era though has since nearly disappeared from Michigan.
Slow growing, plants take 5 years to mature.
The deeply-cut, pinnately-lobed leaves, up to 36 ( rarely over 18 ) inches in length, are oriented north and south. The deep green leaves clasp the hairy white stems. The foliage turns to yellow during autumn.
The bright yellow daisy-like flowers, up to 5 inches across, are borne in clusters during mid summer to early autumn.
Up to 100 flowers may be borne on a plant at a time.
Hardy zones 3 to 8 in full sun to partial shade on deep, slightly alkaline or neutral soil. Clay and salt tolerant. The very deep taproot up to 13 feet deep on mature plants enable it to tolerate severe drought.
* photo taken on Aug 5 2017 @ Brookside Gardens, Wheaton, MD
* photo taken on July 10 2024 @ Brookside Gardens, Wheaton, MD
Silphium mohrii ( Mohr's Rosinweed )
Also called Cumberland Rosinweed. A clumping perennial, reaching up to 6 x 6 ( rarely over 5 ) feet in size, that is native to the southeastern U.S. ( from central Tennessee; south to central Alabama to far northwest Georgia ). It is endangered with extinction, has disappeared from most counties within its range in Alabama and is only found in one county in Georgia ).
The large, lance-shaped leaves, up to 10 x 5.5 ( up to 16 for basal leaves ) inches in size, are very hairy and mid-green. The leaves are alternately-arranged and the leafstalks are up to 6 inches in length.
The bright yellow flowers, up to 2 inches wide, are borne all summer long.
Hardy zones 6 to 8 ( est ) in full sun to partial shade on sandy or gravelly, well drained soil. It is drought tolerant and very heat tolerant.
* photo taken on Aug 24 2017 @ U.S. Botanic Garden, Wash. DC.
Silphium perfoliatum ( Cup Plant )
A fast growing, upright, large clumping perennial, reaching a maximum size of 12 x 4 ( rarely over 5 ) feet, that is native to prairies and moist open woods in central North America ( from eastern North Dakota to northern Wisconsin to southern Michigan to southern Ontario to northeast Pennsylvania; south to southwest Kansas to Oklahoma to central Mississippi to central North Carolina ). It is critically endangered in Ontario where most remaining plants occur in floodplain along the Thames River. In the Windsor/Essex County, Ontario region; it was found around Windsor as well as on the Detroit River islands during the 1800s. It also occurred locally on the Ohio shore at that time where it was locally common at the Castalia Prairie and along the Vermillion and Huron Rivers. It is also endangered in Michigan, the Virginias and North Carolina. Cup Plant can be used as a specimen plant or as a perennial hedge. With time the Cup Plant may form a large clump as it slowly spreads by means of rhizomes. A spectacular large perennial, it has massive untapped potential as a low maintenance landscape plant.
The oppositely arranged, coarse, irregularly toothed, ovate leaves, up to 14 x 6 inches in size, are deep blue-green. The foliage often turns to yellow during autumn. The leaves clasp the stems forming a cup where they unite.
The showy, yellow, daisy-like flowers, up to 4 inches across, are borne during mid-summer to mid-autumn.
The stems are 4-angled.
Hardy zones 3 to 8 in full sun to partial shade on fertile, well drained soil. It tolerates temporary flooding on floodplains but not swampy sites. Salt tolerant.
* photos taken on Aug 25 2011 @ Scott Arboretum, Swarthmore, PA
* photo taken on Aug 20 2011 @ Brookside Gardens, Wheaton, MD
* photo taken @ U.S. Botanical Garden, Wash., DC on Aug 25 2014
* photo taken by Douglas Ladd @ USDA-NRCS PLANTS Database. Midwest wetland flora
* photos taken on July 11 2014 in Washington, DC
* photos taken on Apr 23 2017 @ Brookside Gardens, Wheaton, MD
* photos taken on May 27 2017 @ Meadowlark Botanical Gardens, Vienna, VA
* photos taken on Aug 5 2017 @ Brookside Gardens, Wheaton, MD
* photos taken on Aug 30 2021 @ U.S. National Arboretum, Washington, DC
* photos taken on Aug 1 2022 in Brookside Gardens, Wheaton, MD
Silphium radula ( Roughstem Rosinweed )
A fibrous-rooted perennial, reaching up to 8 x 3 ( rarely over 6 ) feet in size, that is native to rocky, open woodlands in the south-central and southeastern U.S. ( from central Oklahoma to central Missouri; south to central Texas to southwest Louisiana to central Alabama to central South Carolina ). It likely once grew in far southeast Kansas and far western Tennessee but became extinct before discovery. It has not been seen in Georgia since 1948 ( once native to 3 counties there ) and is nearly extinct in Mississippi & Alabama ( remains in 1 county each ). It is a stunning plant for the back of the landscape border.
The stem-clasping, ovate to triangular leaves, up to 9 x 3 inches in size, are gray-green to deep green. The lower stems are usually oppositely-arranged, the upper leaves are often alternate.
The very abundant, bright yellow flowers, up to 3 inches wide, are borne all summer long.
The stems are densely white haired.
Hardy zones 6 to 9 ( possibly 5 ) in full sun on just about any well drained soil. It is very tolerant of heat and drought.
* photos taken by Clarence A. Rechenthin @ USDA-NRCS PLANTS Database
Silphium simpsonii ( Simpsons Rosinweed )
Also called Silphium asteriscus var simpsonii. A clumping perennial, reaching up to 5 feet, that is native to the southeastern U.S. ( from southeastern Alabama to South Carolina; south to northern Florida ).
The attractive, large, lance-shaped leaves, up to 10 x 2 inches in size, are deep green.
The bright flowers, up to 2 inches wide, appear from mid-summer into early autumn. They attract butterflies.
Hardy zones 6 to 9 in full sun on just about any well drained soil.
Silphium terebinthinaceum ( Prairie Dock )
A moderate growing, very long-lived, clumping perennial, reaching a maximum height of 10 x 6 ( rarely over 8 ) feet, that is native to prairies in central North America ( from Minnesota to central Wisconsin to Saginaw, Michigan to southern Ontario to northern Ohio; south to northern Arkansas to central Alabama to central North Carolina ). It is endangered in Ontario. In the Windsor/Essex County, Ontario region; it was found along the Detroit River, especially at the Ojibway Prairie in Windsor, around Amherstburg as well as Ohio shore during the 1800s. On the Ohio shore, it large numbers of it occurred at the Castalia and Oxford Prairies. It was abundant in Detroit, Michigan during presettlement.
The upright, toothed, cordate-triangular leaves are up to 3 x 1 feet in size. The foliage is glossy deep green, often turning to yellow during autumn.
The abundant, golden-yellow, daisy-like flowers, up to 2 inches across, are borne during late summer.
Hardy zones 3 to 8 in full sun on well drained soil. Very drought tolerant due to its deep taproot. Salt tolerant.
* photos taken on May 25 2018 in Columbia, MD
* historic archive photos
* photo taken on Nov 10 2020 @ Brookside Gardens, Wheaton, MD
* photo taken on May 6 2024 @ Brookside Gardens, Wheaton, MD
* photos taken on July 10 2024 @ Brookside Gardens, Wheaton, MD
* USDA-NRCS PLANTS Database
Silphium wasiotense (Appalachians rosinweed)
A perennial, reaching up to 4 x 2 feet, that is native to dry open forest clearings in eastern Kentucky & Tennessee. It is fibrous rather than tap rooted. It is endangered and can only be found remaining in a few counties in the wild.
The cordate-ovate leaves are up to 11 x 8 inches in size. The foliage is deep green.
The bright yellow flowers appear during late summer into early autumn.
Hardy zones 5 to 9 in full sun to partial shade on well drained soil. It is tolerant of dry shade and drought.
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