Paleleaf Woodland Sunflower is a native erect perennial that grows from 3 to 8 feet in height. The smooth stem may have a whitish bloom.
Leaf: It has opposite leaves (can be alternate at the top of the stem) that are thick and rough with 3 noticeable veins rising from the base. They usually have a pale color beneath due to the abundance of white hair. The underside is also usually densely gland-dotted. Leaves are lance-like to slightly oval - especially the larger lower ones. They are either entire or have very shallow teeth. Bases are wedge shaped (cuneate) to sub-cordate. Leaf stalks on lower leaves are at least 1/4 to 1-1/8 inches long (1 - 3cm) and with wings.
The floral array has single flower heads on short stalks (1 - 9cm) from the upper leaf axils. Three to 15 heads can develop per plant. Heads are cylindric to hemispheric in shape.
Flower: Flowers are of two types, ray florets and disc florets. The central disc has 35+ disc florets with yellow corolla tubes with 5 pointed yellow lobes at the opening. These are bisexual and fertile with 5 stamens that have dark reddish-brown anther appendages; the stamens tightly surround a single style which has a bifurcated tip. These florets are surrounded by 10 to 20 ray florets with yellow corollas and rays. The rays are 12 - 20 mm long and without glands on the back side. These are not fertile. The entire flower head is 1-1/2 to 4 inches wide. The flowerhead is enclosed in a series of green phyllaries (bracts) that number 18 to 25, are pointed and slightly spreading, lanceolate in shape and the margins usually have fine hair.
Seed: Fertile flowers produce a dry cypsela that has two small awns and is 4 to 5.5 mm long. Seeds are disbursed by dropping or by the wind. Like most seeds of Helianthus these require at least 30 days of cold stratification for germination.
Habitat: Paleleaf Woodland Sunflower grows from a rhizomatous root system in open woods, prairies, meadows where there is a partial sun, moist to mesic moisture and sandy to loamy soils.
Names: The genus Helianthus is from two Greek words, helios for 'sun' and anthos for 'flower'. The species strumosus is Latin for "having soft swellings". The author name for the plant classification - 'L.' is for Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.
Comparisons: This species is quite variable in leaf shape and amount of leaf hair. It also can hybridize with other sunflowers such as H. hirsutus, Stiff-haired Sunflower and H. tuberosus, Jerusalem Artichoke, making visual identification difficult. The images below show some of the characteristics of hybridization - especially in the leaves, although the stem is completely smooth which is distinctive of H. strumosus.
The species of Helianthus currently in the Garden are: H. hirsutus, Stiff-haired Sunflower; H. pauciflorus ssp. pauciflorus, Stiff Sunflower; H. tuberosus, Jerusalem Artichoke; and Helianthus giganteus, Giant Sunflower.
Above: 1st photo - The outer ray florets number 10 to 20 and the disc florets number 35+. 2nd photo - The phyllaries of the flower head are pointed and slightly spreading, with margins usually hairy as seen here.
Below: 1st photo - The floral array has solitary stalked flowers, usually at least 3 develop, at the top of the plant. 2nd photo - The smooth stem with a whitish bloom. Note also the leaf stalks are at least 1/4 inch long. 3rd photo - leaves are thick and rough with 3 noticable veins.
Below: 1st & 2nd photos - The underside of a leaf with whitish hair that gives it a pale color. 3rd photo - a lower leaf, which can be more oval in shape - note the winged stalk.
Below: 1st photo - the disc florets have corollas with 5 pointed lobes at the tip, anthers tightly surround the style which has a recurved bifurcated tip. 2nd photo - this stem shows some whitish bloom.
Notes: Eloise Butler recorded planting Paleleaf Woodland Sunflower on May 1, 1912, plants obtained from Kelsey's Nursery in MA. She reported transplanting one from near the Parkway to the Garden in Aug. 1917, and several from Minnehaha in Oct. 1918. Martha Crone did not list this plant as being present in the Garden on her 1951 plant inventory, but it was present again on the 1986 census and on subsequent plant lists. Paleleaf Woodland Sunflower is native to a number of counties in East Central Minnesota, including some of the Metro area, and a few counties in the south. In North America it is found almost everywhere in the eastern half of the continent.
Paleleaf Woodland Sunflower is very similar in appearance to H. hirsutus, the Stiff-haired Sunflower, with which it hybridizes, but is less widely distributed. There is some difference and confusion in the common names applied to this plant. Some sources such as the Minnesota DNR List of Native Plants don't refer to it as "Pale-leaved" but call it the Woodland Sunflower which conflicts with an alternate name for H. divaricatus. The U of M Herbarium calls it "Paleleaf Woodland Sunflower," which is the name we use here, whereas Flora of North America prefers "Rough-leaved Sunflower," - another reason to use scientific names. There are a total of 12 species of Helianthus native to Minnesota.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"