Cold stratify the seeds by placing them on a damp paper towel inside a plastic bag (or simply put the unopened seed packet in the fridge) for 3 to 4 weeks.

Sow stratified seeds in moist seed-starting mix, pressing them gently onto the surface and covering with just a thin layer of soil. Marshmallow seeds need light to germinate.

Place the tray in a warm, bright location around 68-72°F. Seeds typically germinate in 1 to 3 weeks, with uneven emergence.

Once seedlings have several true leaves and night temperatures are reliably above 50°F, harden off gradually over a week. Transplant outdoors 18 inches to 2 feet apart in full sun with rich, moist soil.

Mulch with 2 to 3 inches of compost or shredded leaves to hold moisture and suppress weeds during the first season. Water consistently.

Allow plants to grow undisturbed for 2 to 3 years, harvesting only leaves and flowers in the meantime if desired.

In the second or third fall, harvest roots by lifting the entire plant with a wide spade, taking a portion of the roots, and replanting the crown to maintain the patch.

Wash roots thoroughly, chop into thin slices, and dry in a dehydrator at 95-105°F for 12-24 hours until they snap cleanly when bent. Store in a sealed jar away from light.