Valerian

Start seed shallow - valerian needs light to germinate

Sow into flats or a prepared bed and cover no deeper than half an inch (1 cm), pressing the seed into contact with damp soil rather than burying it. Seed started in a greenhouse can be moved out after your last frost. Valerian seed requires light to germinate, so seed buried deeper than about half an inch never gets the signal to break dormancy.

Set transplants on 12 to 15 inch centers after last frost

Move seedlings out once the ground can be worked and frost has passed, spacing them 12 to 15 inches apart into moist, rich loam at pH 6.0 to 7.0. Full sun gives the sturdiest plants, though partial shade is tolerated. A plant that reaches three to five feet tall needs that footprint to build root mass, and tight spacing raises total yield per acre but produces lighter individual roots - the trade you are making at planting.

Keep soil consistently moist through summer

Water through dry spells to hold the soil evenly moist. Valerian will take occasionally dry or occasionally wet ground, but it does not thrive in either. This is a plant of cool, rainy woodland edges, and consistent moisture is the condition it grows fastest under - a root crop that checks in a drought does not catch back up.

Feed nitrogen - it drives the root you are growing for

Apply a standard NPK fertilizer as growth resumes, and side-dress established second-year plants with compost. Extra nitrogen is the single most important input in valerian cultivation, because the crop is the root and top growth is what fills it.

Lift and divide the whole planting every third year

Every three years, dig the entire planting, split the crowns, and replant the best divisions at fresh spacing. Divisions come true where seedlings vary. Valerian spreads by rhizome into a crowded clump, and crowded crowns compete with themselves for the moisture and nitrogen that would otherwise go into root.

Cut the flower heads off before they set seed

As the white-pink clusters open, cut the flowering stalks out at the base. Do not let a single head go to seed if you are anywhere near wild ground. Flower removal is standard practice in valerian production to prevent weedy seedling establishment, and the plant spreads by both seed and rhizome once it gets loose.

⚠ Valeriana officinalis is listed as a noxious weed in Connecticut and Wisconsin and has escaped cultivation across the northern US, where it displaces native plants along shores and woodland edges. Check your state's noxious weed list before planting, and deadhead without fail.

Dig roots in fall, after frost - and consider year one, not year two

Dig whole roots in fall after the first frost, once the top growth has been knocked back and yellows to the ground. Wash them, then dry in the shade with a gentle air flow and low heat, under 100F (40C). Frost signals the plant has moved its reserves down into the root, which is where the sedative compounds sit. Drying hot or in sun drives off the essential oil you dug the plant for.

⚠ Montana State University WARC trials (agresearch.montana.edu/warc/research_current/research_past/herbsandoils/valerian.html) found first-season roots yielded 3,126 lb/a with no disease, while two-year plants yielded 809 lb/a and developed Phoma root rot; that trial concluded growing valerian as an annual may be the best practice where disease is present. If you have lost second-year plantings to rot, harvest at the end of year one instead of waiting.