Turtleheads have flowers where the upper lip arches over the lower lip giving the resemblance to a turtle's head. White Turtlehead is a native erect perennial forb growing on smooth 4-sided stems, usually about 2 to 4 feet high (some to 7.5 feet) and usually unbranched below the inflorescence, but branched within. Stems are usually multiple from the root.
The leaves are long, 6x as long as wide, 9 inches at the longest, lance shaped, sharp toothed, opposite, and hairless. They have pointed tips, are narrowed at the base - the lower stem leaves are toothed, taper to a short stalk, while the upper leaves can be clasping and have margins without teeth. The upper surface is smooth while the lower surface can vary from smooth to finely hairy. Each pair is usually rotated 90 degrees from the adjacent pair on the stem. The leaves of Chelone contain two chemicals which deter a number of plant browsers from eating them - the chemicals, metabolites, are iridoid glycosides aucubin and catalpol. (see reference article at page bottom)
The inflorescence is a dense short spike at the top of the stem and on axillary stems from the upper leaf axils. Flowers open from the bottom to the top of the spike.
The white flowers (can have a pink tinge) have two almost closed lips. The upper lip has two shallow lobes. The lower lip has three lobes with the center one bearded inside. The flower tube is 1 to 1-1/2 inches long. Inside are 5 stamens and a style. The short style and four of the stamens that are true are appressed to the upper part of the corolla tube in pairs, almost joined, until forced apart by large bees. The pollen sacs of these stamens are covered with dense hairs. The fifth sometimes degenerated stamen (a staminode) is short, has a green tip and usually lies at the base of the tube. The green calyx has 5 ovate-oblong segments with rounded lobes. At the base of the calyx are several green bracts with smooth surfaces.
The Chelone genus is protandrous, that is the male segments of the flower mature before the female parts. When the pollen sacs mature, attracting large bees, nectar production is low, but then the flower enters the female phase and the style, formerly recessed in the upper lobe, elongates and recurves downward, placing the stigma near the entrance to the corolla and in front of the anthers, thus picking up pollen from late pollen gathering bees as they leave the flower. These late bees are also now attracted by an increase in nectar projection. Thus Chelone even though it is protandros, can set seed from its own pollen (autogamous) but requires a later second visit by a pollen gathering bee to do so. (Reference below).
Seed: Fertile flowers produce an ovoid seed capsule, twice as long as the calyx, containing flatten seeds that have wide wings for wind dispersal. Turtlehead seeds are best planted outdoors in the fall as the seeds need at least 120 days of cold stratification for germination.
Habitat: Turtlehead grows from a rhizomatous root system which allows it to colonize. It requires fertile moist soil and full sun for stout plants. These plants appear in a few places in the bog area of Eloise Butler but are greatly outnumbered by the Red Turtlehead.
Names: The genus name Chelone from the Greek chelon, 'tortoise' and the species name glabra means 'smooth' - no hair on the calyx, stem and, most of time, on the leaves 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. The newest reclassification puts this plant into the Plantaginaceae (Plantain) family and removes it from the Figwort (Scrophulariaceae) family.
Comparison: Red Turtlehead, Chelone obliqua, has a similar flower, but pink in color and the leaves are distinctly different, being more ovate, a longer stalk and a different vein pattern.
Above: Detail of the inflorescence. In the 2nd photo note the multiple spikes on branches from the main stem.
Below: 1st photo - the entrance to the corolla is restricted to larger pollinators - particularly Bumble Bees. 2nd photo - The green calyx has five lobes with rounded tips
Below: 1st photo - The upper stem leaves can be clasping have margins without teeth, while the lower stem leaves (2nd photo) have a very short stalk at the 4-angled stem, sharp teeth, and an intricate vein pattern.
Notes: White Turtlehead is indigenous to the Garden area. Eloise Butler catalogued it on Sept. 6, 1907. She obtained additional plants from Malden, Mass. in Sept. 1909. It is listed on Martha Crone's 1951 census of Garden Plants. She had also planted it in 1946. White Turtlehead is native to Minnesota in most counties in the East half of the State which marks the western edge of the plants range in the U.S. It is found in the eastern half of North America, from the Mississippi River eastward in the U.S. and Manitoba eastward in Canada. This is the only species of Chelone currently found in the wild in Minnesota as documented on the 2019 DNR census reports. The Red Turtlehead (Chelone obliqua) is considered native to Minnesota but distribution in the state is not well documented. The Checklist of the Vascular Plants of Minnesota (Ref. #28C) still lists the plant.
Eloise Butler wrote this story about the plant: "A turtle takes a daily sunning on a rock in the little pond in the wild garden. His tail held stiffly erect suggested to someone a marlingspike, the tool that is associated with a boatswain. Accordingly the turtle was dubbed Bos’n, and a little one that has lately appeared, Bos’nette. Very appropriately, a plant with white-flowered spikes, named Chelone (turtle) [C. glabra L., Turtlehead] graces the sides of the same pond. It is easy to understand how the name Turtlehead was applied to this plant growing in the damp places that turtles frequent, when one has an opportunity to compare the lips of the animal with those of the flower." Published 17 September, 1911, Minneapolis Sunday Tribune. Read article
Technical Reference: A paper titled POLLINATION ECOLOGY AND FLORAL VISITOR SPECTRUM OF TURTLEHEAD by Richardson and Irwin was published in 2015 in the Journal of Pollination Ecology. It reports of research of how pollination is accomplished in the Chelone genus. [PDF copy]
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"