Wood Poppy is a North American native (not to Minnesota) perennial woodland forb that grows to 1-1/2 feet tall on hairy green stems that have some branching. Stems are hollow and along with the leaves, contain an acrid orange juice.
The leaves are opposite, lobed and deeply divided - referred to as twice pinnatifid. Pinnatifid means that the lobes along the primary leaf rib are not cut all the way to the rib and thus do not make actual separate leaflets. Twice pinnatifid means that the individual side lobes are cleft but also not all the way down to the side lobe midrib - as a glance at the photo below will show. Margins of the lobes have large rounded teeth - (are crenate). Leaf stalks and midribs of the lobes have a few hair. Most leaves are basal and stalked, but flowering stems have a pair of leaves 2/3rds of the way up the stem on shorter stalks.
The inflorescence is a single flower or a small umbel of 2 to 4 flowers.
Flowers have a beautiful deep shinning yellow corolla (like a Marsh Marigold), up to 2 inches wide, dividing into 4 petals with wavy edges. The calyx is very short with 2 green sepals that drop away early. The flower is perfect, with numerous stamens with yellow anthers and a single green pistil with a knob-like stigma. The ovary normally has four carpels but can have as few as two.
Seed: Flowers mature to a seed capsule that is ellipsoid in shape and covered with many long hairs and tipped with the persistent style. The capsule normally has four chambers which contain a number of pale brown to dark brown reticulated seeds. These seeds have a white fringe of small oil bodies. When mature the 4 sides of the capsule split and reflex outward from the tip and expose the seed for release. For germination, seeds require a warm moist period, followed by a cold moist period.
Habitat: Wood Poppy grows from rhizomes which can spread the plant vegetatively but it is not a rapid grower. If seed pods mature, the plant can easily self-seed. It needs the rich moist soil of the deciduous woodland, sunlight prior to tree leafout and shade or dappled shade thereafter. It can remain vigorous throughout the season if not allowed to dry out. Repeat flowering can be encouraged by dead-heading.
Names: The genus, Stylophorum is from two Greek words - stylos, meaning 'style' and phoros, meaning 'bearing' and together referring to the prominent style of this genus carried over to the seed capsule. The species, diphyllum, is also from the Greek di for 'two' and phyllon for 'leaf' referring to the pairs of opposite leaves on the flowering stems. The names of the authors of the plant classification are as follows: First to publish was ‘Michx.’ which refers to Andre Michaux (1746-1802), French botanist who made many exploring expeditions in the U.S. collecting and cataloging many species. His notes were later used by his son, Francois, who with Thomas Nuttall published the multi-volume North American Sylva. Michaux's work was amended by ‘Nutt.’ who is that same man that worked with Francois Michaux - Thomas Nuttall (1786-1859) English botanist who lived and worked in America from 1808 to 1841. On his many expeditions he collected many species that had been originally collected by Louis and Clark but lost by them on their return journey.
Comparisons: Wood Poppy is similar in appearance to a poppy introduced from Europe, the Celandine Poppy, Chelidonium majus L., which is found naturalized in most of the eastern half of North America including Minnesota. It has smaller flowers, less that 3/4 inch, and hairless seed capsules. That plant is quite weedy and should be avoided.
Above and Below: The flower has a hairy stalk and appears singly or in groups of 2 to 4. Flowers will bloom for an extended period with adequate moisture. Illustration by William Curtis.
Below: 1st photo - The prominent light green style with the knobby stigma is the source of the genus name Stylophorum. 2nd photo - The leaf is twice-pinnatifid and the pair of opposite leaves that are on flowering stalks give rise to the species name diphyllum.
Below: 1st photo - Seed capsules with dense hair distinguish this species from confusion with other yellow poppies. 2nd photo - The root is rhizomatous allowing vegetative reproduction.
Below: The seed capsule has four chambers which contain a number of pale brown to dark brown reticulated seeds. These seeds have a white fringe of small oil bodies. When mature the 4 sides of the capsule split and reflex outward from the tip and expose the seed for release.
Below: 1st photo - The brown reticulated seeds of Wood Poppy. 2nd photo - Stems are hollow and along with the leaves, contain an acrid orange juice.
Notes: Eloise Butler's records show that she obtained plants of Wood Poppy on April 22, 1911 from Brownsville Ohio. Wood Poppy was listed on Martha Crone's 1951 inventory of plants in the Garden at that time. Wood Poppy is not native to Minnesota but is native to a group of states From Michigan, Pennsylvania, the Ohio Valley, New Jersey and down through Tennessee, Mississippi and Georgia. It is found in Ontario in Canada. There is a large solitary clump in the Garden near Guidebook station 4. Others have by added by Curator Susan Wilkins along Violet Way in 2009 and 2012.
Rareness in the wild: If you have grown Wood Poppy in your garden you know that the plant requires moist soil to avoid shut-down after the first spring flowering. It can produce flowers later in the season when supplied with adequate moisture. In the wild this may not happen, but while the plant produces many seeds, it does not spread rapidly. Studies have been done in Canada as to why known populations do not spread. First, if the season turns dry, the plant shuts down quickly, leaving little time for vegetative reproduction. Second, the seeds need cold stratification to germinate and are frequently eaten by squirrels before that can happen. In a home garden, given adequate moisture, seed sets well and many new plants may appear in following years. Seedlings also transplant well. (Paper-pdf from North American Native Plant Society)
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.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"