Two-leaved Toothwort is an erect perennial forb of the springtime growing 8 to 16 inches high on an unbranched stem. Bloom time varies with the seasonal weather - from as early as mid-April to as late as mid-May.
The leaves are of two types, basal and stem. The stem leaves number just two, with the two leaf stalks appearing opposite each other or just slightly offset - sub-opposite - hence the common name of "two-leaved." These stem leaves have 3-parted leaflets not deeply cut like Cardamine concatenata - the Cut-leaved Toothwort. The leaflets are shaped the same - broadly elliptic to ovate in shape with coarse dentations on the margins. Each leaflet is either without a stalk or a very short stalk. The basal leaves rise from the rootstock, usually after flowering, and are similar in design to the stem leaves.
The inflorescence is a tall loose cluster of stalked flowers rising on a single central stem (a raceme) above the leaves. The stalk of the cluster and the individual flower stalks can be green to reddish in color and can have some very fine hair. There are no bracts to the cluster. Like many Mustard family plants, the raceme elongates as the flower buds begin to open.
The flowers are 4-parted, small (usually less than 2/3 inch wide) with a tubular calyx that has 4 light green oblong sepals with obtuse tips. The four petals are white to pinkish, much longer than the sepals and have rounded tips. The reproductive parts include six stamens where the two inner pair have filaments (white) longer than an outside pair. Anthers are linear, yellowish-green in color. There is a single style, reddish toward the globose shaped stigma.
Seed: Mature flowers can produce a linear dry pod (called a silique), usually ascending, that contains oblong brown seeds. However, this species rarely produces seeds but when it does the pod splits open with a twist to eject mature seeds. Seeds usually require at least 60 days of cold stratification for germination. Divisions of the root are used for propagating.
Habitat: Toothwort grows from a horizontal un-segmented rhizome which can spread producing colonies of plants. It requires moderate moisture levels, rich soils such as in woods, woodland edges. Full to partial sun is needed up to flowering, then partial to full shade for the summer. Located in the Eloise Butler Woodland Garden in various places.
Names: "Toothwort" refers to the rootstalk, not of this species, but of C. concatenata, which has teeth-like segments that resemble a string of beads or "teeth" as some observe. The name is kept for C. diphylla due to the similarity of the plant. Botanists have recently placed this plant into the genus Cardamine instead of the former Dentaria where the plant was called Dentaria diphylla. The species name diphylla is Greek, referring to "two-leaved." Cardamine is derived from the Greek kardamon, the Greek name for a certain cress (also in the Mustard family). Plants assigned to this genus of the Mustard family have stem leaves, linear ovaries, very short sepals, seeds flattened in pods that split open when mature, stems that do not root at the nodes and rhizomatous roots.
The author names for 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. Two important works of his are the Histoire des chênes de l'Amérique septentrionale (1801 - Oaks of North America), and the Flora Boreali-Americana (2 vols., 1803) published posthumously, in which was the description of this plant. His son Francois, traveled with him and the father’s notes were later used for the 3-volume North American Sylva. Michaux's work was updated by ‘Alph. Wood’ which refers to Alphonso Wood (1810-1881) American botanist and Professor of Botany at the Female Seminary of Cleveland Ohio. He wrote several books on botany that made scientific research available for distribution as textbooks. His name is sometimes listed as A.W.Wood.
Comparisons: Toothwort has similar appearing flowers to C. concatenata, the Cut-leaved Toothwort but on that species the leaflets are very deeply cut into palmate divisions and the stem leaves are usually 3 in a whorl, although there can be only two. It usually sets seed in the silique and the rhizome is segmented.
Above: Flowering time varies considerably with the spring weather. 1st photo - - from mid-May 2009; 2nd photo - from mid-April 2012. Note the much smaller size of the green sepals compared to the petals.
Below: Fine example of Two-leaved Toothwort. Drawing from Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York.
Below: 1st photo - the inflorescence is a loose cluster in the form of a raceme, which elongates as the flowers open. 2nd photo - The twin opposite 3-lobe stem leaves from which the plant gets its common name of "Two-leaved."
Below: Here you can see that the two pair of stamens that are closest to the style are longer than the separated pair nearest the petals.
Below: The silique (or seed pod) is linear and similar looking to many Mustard family plants.
Below: A large colony of plant in the Woodland Garden.
Notes: Toothwort is not indigenous to the Garden or any part of Minnesota. Eloise Butler noted planting it in 1911 with plants she obtained from Gillett's Nursery in Southwick, MA. More were planted on May 1, 1912, again from Gillett's. Two-leaved Toothwort was listed on Martha Crone's 1951 inventory of plants in the Garden at that time and probably has been in the Garden continuously. They are very long-lived plants as there is no record of replanting after 1912.
It has reported distribution, including native status, to certain unspecified parts of Minnesota, but Minnesota is at the plants extreme western range in the U.S. and the plant is an introduction here, as it is in the Garden. The DNR does not consider it native and the U of M reports that there are no collected plants in the Herbarium. Further proof would be that there is no reported distribution in Wisconsin in any counties near Minnesota, nor any distribution in Iowa. The prominent native variety of Toothwort is the Cut-leaved Toothwort, Cardamine concatenata.
There are 6 native species of Cardamine found in Minnesota: C. bulbosa, Spring cress; C. concatenata, Cut-leaved Toothwort; C. impatiens, Narrowleaf Bittercress; C. parviflora, Small-flowered Bittercress; C. pensylvanica, Pennsylvania Bittercress; and C. pratensis, Cuckoo Flower. C. pensylvanica is also found in the Garden.
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"