Culver’s root (Veronicastrum virginicum) is a hardy perennial that is native to the eastern United States and south-eastern Canada. It is also known as Culver’s physic or black root. The name “Culver’s root” refers to Dr. Culver, an 18th century physician who used the root of the plant as a purgative. Native Americans, of course, had been using the root as a laxative for hundreds of years before that. They also used it as a liver tonic.
Culver’s root is hardy in zones 3 – 8. It grows 4 to 7 feet tall (including the flowers) and 2 to 4 feet wide. Its leaves are lance-shaped and grow in whorls around the stems, 3 to 7 leaves per whorl. The plants will spread over the years, but slowly. They are not invasive. The flowers resemble veronica flowers, growing in 9-inch racemes of tiny, tube-like flowers that are usually white, but can also be blue or light purple. Smaller lateral racemes make the flowers look like candelabra. The blooms last about a month. Removing the spent racemes can prolong blooming. Bloom-time is mid-June to late August depending on the latitude. They will self-sow, but not enough to make them invasive.
Culver’s root grows best in full sun. Despite their height, they don’t normally need staking. They will tolerate a little shade, but in the shade the plants may need to be staked. The plants will grow in almost any soil, but prefers moist, well-drained soil. It’s best not to let the soil dry out. The plants can be grown in rain gardens. Because these are native plants, they do not require any fertilizer.
Culver’s root can be divided. It is recommended that you divide your plants in May. I prefer to divide my perennials in the fall so they have a chance to settle in and grow out their roots before winter. That way in the spring they will begin growing and blooming without a delay caused by division and replanting.
These plants are easy to grow from seed. You can sow your seeds in either the spring or the fall. If you are sowing in the spring, bear in mind that they need a 3-month period of cold stratification. You can do this in your refrigerator. Sow your seeds in a container of moistened soil, cover it with a plastic bag and put it in your refrigerator for three months. Check the container periodically to make sure that the soil is still wet. If it begins to dry out, you can mist it to moisten it again. Or you can sow your seeds in the fall outdoors in your garden and let Mother Nature cold stratify them for you. Surface sow the seeds. Do not cover them with soil. They need sunlight to germinate.
If you are growing your seeds indoors, you can plant your seedlings out in your garden after your last frost. Space them 2 feet apart.