Blue vervain is an herbaceous perennial that is hardy to USDA zones 3 to 9.
Blue vervain is an upright plant with square, greenish-red stems and opposite, lance-shaped leaves that are coarsely toothed. Despite the square stem and opposite leaves, blue vervain is not a mint but a striking member of the Verbenaceae family that is native to North America and found throughout Canada and the United States. Blue vervain grows four to five feet tall, and has clusters of two to five inch spikes that are composed of individual flowers. These small flowers are less than a quarter inch wide and bloom intermittently, a few flowers at a time, starting at the base of spikes, then spiraling upward. Vervain is a favorite among pollinators and attracts both bees and butterflies.
Blue Vervain likes full sun but can tolerate partial shade and in the wild grows well in open fields, meadows, prairies, and stream / riverbeds. Blue vervain does well in well-drained soil containing good fertility and organic matter. It is not drought tolerant and needs and adequate amount of water.
The seeds of blue vervain germinate well if stratified and are sown in early spring. The seeds are not light dependent germinators and should be lightly covered with potting medium after planting. Once stratified in the cold, the seeds should germinate in warm soils in two to three weeks. In Washington, we prefer to sow seeds into trays, then transplant well-established plugs.
Blue vervain can grow very tall and is striking when it goes to bloom. It makes a lovely hedgerow and is good to plant on the edges of beds. Blue vervain is not susceptible to pests and disease and can be planted near most perennials. The only consideration would be sure it is not shading out lower-growing plants that require full sun. We commonly plant it next to echinacea and black cohosh. Blue vervain can also be propagated from root divisions or vegetative cuttings. Plant blue vervain with twelve-inch spacing in the row and twenty-eight-inch spacing between rows.
The leaves and flowers of blue vervain are traditionally used as a nervine (nervous system tonic) and can be especially effective at easing nervous tension that manifests as stiffness or rigidity in the neck, shoulders, and back. Blue vervain can also help provide relief to women who experience irritability around their menstrual cycle, and it is useful in alleviating nervous depletion and exhaustion. As a nerve tonic blue vervain is valued for its slightly sedative effect and has been used for anxiety and depression by helping the body relax and release wired energy and stress. Some people report feeling more expansiveness and feeling calmer after taking blue vervain. In addition to its nervine properties blue vervain is used to reduce fevers by promoting sweating, and it also contains bitter properties that help to ease sluggish digestion. The flowers and leaves are used internally as tea, tincture, or flowers essence. They can also be used topically in liniments, oils, or salves.
The medicinal propertis of blue vervain are at their peak when the plant begins to flower in mid to late summer. Harvest both leaf and flower by using a field knife to cut the entire aerial part of the plant, leaving about twelve inches at the base for regenerative growth. In some areas it is possible to get a second cutting from well-established plants. Harvest the leaves and flowers on bright, sunny days, when the plant is dry and free from dirt or debris, preferably not after rain events that could splash soil onto the lower leaves.
Post Harvest Drying Conditions
Blue vervain is easy to over dry and can lose its medicinal properties quickly, so it should be processed quickly at lower temperatures. Dry on racks in temperatures of 90 to 95 degrees F. When racking blue vervain, place he herbs in a single layer to allow for good airflow and uniform drying. Under optimum conditions blue vervain should be dry within forty-eight hours. To process, garble the plants over a garbling rack made out of quarter to half inch stainless teal mesh, and remove stems. Blossoms will crumble off with the leaves, and they should be mixed together. The deep green leaves and bright purple flowers make for a vibrant blend.
Pests and Diseases
Blue vervain is minimally susceptible to insect damage and foliar disease, and the health of this crop can be maintained by good cultivation practices and crop rotations.