Cold stratify the seeds for at least 21 days by placing them on a damp paper towel inside a plastic bag (or simply put the unopened seed packet) in the refrigerator. Keep the towel barely moist throughout the cold period.

After stratification, lightly scarify the seeds by rubbing them gently between two pieces of fine-grade sandpaper for about 30 seconds. This nicks the hard seed coat just enough to let water penetrate.

Soak the scarified seeds in lukewarm water overnight to fully hydrate them before planting. Discard any seeds that float and stay shrunken after a long soak, since those are duds.

Sow the prepared seeds in small pots of moist seed-starting mix about 8 weeks before your last spring frost. Plant each seed about 1/4 inch deep and water gently. Germination typically takes 3 to 10 days at room temperature.

Once seedlings have several true leaves and outdoor temperatures are reliably above 50°F at night, harden off gradually over a week by exposing them to outdoor conditions for increasing periods.

Transplant outdoors 16 to 18 inches apart in a sunny, well-drained spot with sandy or loamy soil. If you have heavy clay, amend with sand and compost or plant in a raised bed.

Water deeply during prolonged dry spells but otherwise provide minimal care. Top-dress with compost in spring for steady fertility, and avoid high-nitrogen fertilizers that produce lush leaves at the expense of medicinal compounds in the roots.

Allow plants to grow undisturbed for at least 2 years before harvesting, with 3 to 4 year old plants producing the largest and most potent roots. The first growing season is mostly about establishing the root system.

Harvest in late fall after the foliage has died back. Water the plant thoroughly the day before to soften the soil, then use a garden fork or sharp spade to dig a wide circle around the plant and lift the entire root mass.

For sustainable harvest, take no more than a third of the root mass and replant the crown immediately at the same depth, watering in well. The plant will recover and produce another harvest in a year or two.

Wash the harvested roots thoroughly under running water, scrubbing between your fingers to remove all soil from the crevices. Slice the cleaned roots into thin pencil-thick coins.

Dry the sliced roots in a dehydrator at 95 to 105°F for 12 to 24 hours, until the pieces snap cleanly when bent. Store the dried slices in a sealed glass jar away from light, where they'll keep their potency for at least a year.