Figwort family (Scrophulariaceae)
Description: This plant is a summer annual about 1-2' tall that usually branches abundantly. It is more or less erect. The slender stems are rather angular with flat ridges, green to reddish purple, and hairless to mostly hairless. The opposite leaves are up to 3" long and 1/8" (3 mm.) across; they are green to purplish/reddish green, linear, glabrous, and sessile.
Individual flowers and their buds are produced from the axils of the leaves on the upper and outer stems; these flowering stems can be regarded as leafy racemes. The swollen flower buds are conspicuously white. Each flower is about ½–¾" across, consisting of a short tubular corolla with 5 petal-like lobes and a tubular calyx with 5 short teeth. The corolla is pink, purplish pink, or medium purple; its 5 rounded lobes are quite large in relation to its tubular base. The lobes are finely ciliate along their margins. The lower interior of the corolla has dark purple spots and a pair of faint yellow lines. Near the upper interior of the corolla, there are 4 stamens with hairy white anthers and an undivided white style (sometimes with a pale yellow tip). The slender pedicels of the flowers are green to reddish purple; they are usually as long or longer than the flowers (at least ½" long). The blooming period occurs during the late summer or early fall and lasts about 2-3 weeks. Each flower lasts only a day or two before its corolla falls to the ground. There is no noticeable floral scent. Each flower is replaced by a globoid seed capsule containing many small seeds that can be blown about by the wind. The root system is fibrous. Slender False Foxglove is partially parasitic on other plants.
Cultivation: The preference is full or partial sun, moist to slightly dry conditions, and a rather loose, friable soil containing silt or sand that is slightly to moderately acidic. This species also adapts to thin rocky soil. Its growth is more robust when a suitable host plant is present nearby.
Range & Habitat: Slender False Foxglove is occasional throughout Illinois, where it is native. Habitats include moist to mesic prairies, sand prairies, savannas, sandy savannas, woodland borders, sandstone glades, thickets, low sand flats, silty or sandy roadside ditches, and edges of fields. This species tends to occur in slightly disturbed habitats with infertile soil and sparse ground vegetation. It has low fidelity to any particular habitat.
Faunal Associations: The nectar of the flowers attracts long-tongued bees (bumblebees, honeybees, and Large Leaf-Cutting bees), Panurgine bees (Calliopsis andreniformis & others), and butterflies. Some Halictid bees collect pollen, while Syrphid flies occasionally feed on the pollen. Large Leaf-Cutting bees (Megachile spp.) sometimes cut the petals (lobes) of the flowers for nesting material. Among these various insects, the long-tongued bees and Panurgine bees are more effective at cross-pollination of the flowers (see Robertson, 1929). The caterpillars of the butterfly Junonia coenia (Buckeye) feed on the foliage. Mammalian herbivores may browse on the foliage of Slender False Foxglove, although it is reportedly toxic to sheep.
Photographic Location: The edge of a field in Vermillion County, Illinois. This species was also growing along the roadside in the same area.
Comments: Slender False Foxglove is very showy during the short period in which it is in full bloom. This is the most common and widespread Agalinus sp. in Illinois, probably because it can adapt to a broad range of habitats. There is some variation in the length of the leaves, the presence or absence of fascicled leaves, the size of the flowers, and the color of the flowers across different local populations. Such minor variations have led to the description of different varieties and even different species by some authorities. Generally, Slender False Foxglove differs from many other Agalinus spp. by having flowers with shorter corolla tubes and longer pedicels. In contrast, Agalinus purpureus (Purple False Foxglove) has more elongated flowers (up to 1" long) and shorter pedicels (less than ¼"). Slender False Foxglove also has darker foliage (green to reddish purple) and darker seeds than some Agalinus spp. Members of this latter group (e.g., Agalinus skinneriana) have pale green to yellowish green foliage and pale-colored seeds.