How to Split Red Valerian Plants
Sometimes called Jupiter's beard, red valerian (Centranthus ruber) is a flowering perennial plant favored for its showy magenta flowers and extreme drought tolerance. It thrives in U.S. Department of Agriculture plant hardiness zones 5 to 8, where it will reach a mature height of 1 to 3 feet with an equal spread. Red valerian plants propagate easily from divisions, which can be split from the parent plant every one to three years. The divisions root quickly once replanted in a sunny bed with moist soil. However, they must be taken during the right time of year to ensure success.
Divide red valerian plants in autumn every one to three years. Wait until after the flowers have faded since actively blooming plants put their energy toward flowering rather than root production.
Water the parent plant to a 5-inch depth the night before lifting and dividing it. Prune back the stems by half to limit water loss through transpiration. Use freshly cleaned and sanitized pruning shears to decrease the likelihood of transmitting fungal or bacterial infections.
Measure and mark out a line 3 inches around the base of the red valerian plant. Dig down 6 to 8 inches along the 3-inch mark. Carefully work the shovel blade underneath the root ball and pry it from the ground.
Lift the red valerian plant from the ground and move it to a shady location. Cover it with a moist towel to prevent stress and moisture loss while preparing the planting site.
Work a 3-inch layer of compost into the planting site to improve the nutrient content and moisture retention of the soil. Remove any stones or other debris that might inhibit drainage. Pull up and discard any weeds.
Cut the red valerian root ball into three or four portions, each with an equal share of roots and stems. Cut straight down through the root ball with a sharp gardening knife. Discard the center of the plant if the stems are woody or if the foliage growth is thin and lacks vigor.
Inspect the roots of each division for signs of disease. Snip off any blackened or damaged roots using clean, sharp scissors. Discard any divisions with a significant proportion of damaged or diseased roots.
Dig a planting hole for each red valerian division. Make the planting holes 1 inch shallower than the rootball. Space the holes approximately 12 to 24 inches apart.
Loosen the root ball of each red valerian division. Spread the roots along the bottom of the planting hole. Hold the division so the base of the stems is at soil level. Backfill around the roots until they are covered.
Water the divisions to a 3-inch depth after planting to settle the soil. Spread a 2-inch-thick layer of mulch between the red valerian divisions to help keep the soil moist and to prevent weed growth.
Water the red valerian divisions weekly to a 1-inch depth. Withhold watering during periods of rainy weather to decrease the likelihood of rot or bacterial growth. Watch for renewed growth in spring.
Samantha McMullen began writing professionally in 2001. Her nearly 20 years of experience in horticulture informs her work, which has appeared in publications such as Mother Earth News.