Plant of the Week
Golden Hedgehyssop (Gratiola aurea Pursh, formerly Gratiola lutea)
By Sue Trull
Golden hedgehyssop is a perennial herb in the Figwort or Snapdragon family (Scrophulariaceae). Also known as yellow hedgehyssop or golden pert, it is an amphibious plant that can grow both in a submerged form in shallow lake water and in an emerged form on lake beaches or other damp habitats. The aquatic form of golden hedgehyssop is only about ½ inch tall and is sterile. Emerging from a cluster of roots, the stem is smooth, and somewhat four-angled. The leaves are opposite, long oval, pointed, and usually less than 0.2 inch long. The leaves are stalkless, and have entire margins. This form can be found growing in water up to about 12-13 feet deep.
The terrestrial form is larger, about 4 to 12 inches tall. The out-of-water stems can be erect or creeping, and unlike the underwater stems, they have gland-tipped hairs. Stalkless, the leaves on this form are larger as well, to 1 inch long, and have conspicous glandular dots on top and bottom leaf surfaces.
Shoreline plants produce bright yellow tubular flowers, about ½-inch long, solitary on short stalks from the upper leaf axils. The flowers flare out in lobes at the top of the tube, and have 5 green sepals cradling the tube bottom. The flowers appear in July to September, often after water levels recede, exposing the plants on the shallow lake beaches. Fruits are small, round capsules.
Golden hedgehyssop inhabits shallow water or wet shores, in sand, gravel, mud, or peat. It occurs in full sun. It can occur in acidic to brackish water regimes. In the eastern United States, this plant can be associated with coastal plain habitats. The plant may be locally common, with populations of several thousand plants forming a carpet across the lake bottom and onto the beach. Golden hedgehyssop can occur with other plants such as pipewort (Eriocaulon aquaticum), sedges, rushes, water lobelia (Lobelia dortmanna), waterwort (Elatine minima), or water lilies.
Golden hedgehyssop is listed with Threatened status in Michigan, where it is documented in only one county of the state’s Upper Peninsula; and Endangered status in Pennsylvania, where it is documented only in counties on the eastern border of the state. Lakeshore development; loss of habitat; loss of fluctuations in water depths and shoreline exposure, such as associated with hydropower development; pollution; and introduction of aquatic invasive plants are factors threatening population viability for this plant.
The genus name “Gratiola” is derived from the Latin for “grace”, referring to medicinal properties of the genus (although not this particular species). The species epithet “aurea” comes from “aureus” meaning gold in Latin, referring to the flower color. Interestingly, the flowers of golden hedgehyssop rarely can be white instead of yellow.