Agalinis tenuifolia, slenderleaf false foxglove, is a native herbaceous annual plant that blooms in the late summer with delicate pink flowers with spotted whitish throats. There are several species of Agalinis in NJ. A few features are given here to help with species differentiation. Other common names include slender gerardia after its previous scientific name, Gerardia tenuifolia.
Flowers
Agalinis tenuifolia, slenderleaf false foxglove, has flowers arranged in a raceme. The flowers form along long stems with 2 flowers per node. The flowers have long pedicels (flower stalks).
The flowers are pink to pink-violet. The corolla (flower) tube opens up to 5 rounded lobes.
Within the genus, a differentiating characteristic is the presence of two smaller curved upper lobes which form a hood over the tops of 2 tall anthers. The 3 larger lower lobes flare outward reflexing slightly. The inside of the corolla tube is whitish with the characteristic 2 pale yellow stripes with reddish spots on the lower area.
The flower has a long style that extends out beyond the corolla tube. There are 4 stamens which are not always visible. The two upper anthers with longer filaments are frequently hidden under the upper lobes of the flower. The two lower anthers with shorter filaments are deeper into the flower. The 3rd photo below shows an opened up flower with all 4 hairy anthers and the style.
The flower is about a 1/2 inches wide across the front.
This side view photo shows the corolla tube, calyx and the pedicel (flower stalk). The green calyx is formed by the fusion of the 5 sepals and the 5 sharp teeth are visible. The size and shape of the calyx and relative lengths of the pedicel are frequently used in identification keys for differentiating the Agalinis species. The pedicels are at least a half inch long.
The first photo below shows the conspicuous yellow white buds. The second shows some calyxes after the petals have fallen off and some development of fruit. The dried up stigma sometimes persists into fruit development. Also seen are two flowers per node arrangement.
Leaves and Plant
The leaves are simple, opposite, sessile and narrow, about 3 inches long with a prominent vein down the middle.
This annual plant blooms in the late summer/early fall and grows to about 1-2 feet tall. The stems are simple or branched and are mostly upright. Unfortunately, the flowers only last a day or two. At any one time, not many flowers may be in bloom.
Habitat
Habitat: Wet to dry roadsides, ditches, margins of streams and ponds, borders of woodlands, dry to moist prairies, fallow fields, railroad embankments, rocky cliff faces and bluffs.
All Agalinis spp. are partially parasitic on other plants. The Agalinis plant sets up a connection between its roots and those of a host plant using specialized roots called haustoria. Through the haustoria, it gets sugars and proteins from the host plant.
Agalinis purpurea also grows in similar habitats but its flowers are larger, sessile and the two upper lobes flare out.
Text by Millie Ling and all photos by Hubert & Millie Ling: 8/31/2020, Johnsonburg Swamp Preserve, Sussex County.
Cultivation
There are places on the internet that sell Agalinis tenuifolia seeds
Additional information
Additional information / references:
The USDA website shows its distribution in the US and other information,
https://plants.usda.gov/core/profile?symbol=AGTE3
Flora of North America - tends to use technical terms:
key to Agalinis spp:
http://beta.floranorthamerica.org/Agalinis
description Agalinis_tenuifolia:
http://beta.floranorthamerica.org/Agalinis_tenuifolia
Minnesota Wildflowers has good descriptions of the plant parts:
https://www.minnesotawildflowers.info/flower/slender-leaved-false-foxglove
Illinois wildflowers is also a good source of information:
https://www.illinoiswildflowers.info/prairie/plantx/slfs_foxglove.htm