Fertilizers to Use on Lithodoras

Clues to Good Health

• When planted in soil that provides all its necessary nutrients, purple gromwell's health shines through. The narrow, 1-inch foliage conveys vitality through the deep green color of its dense leaves. Normally growing 3 to 4 inches tall, but reaching 6 to 12 inches in height when cramped for space, a single plant can spread 2 to 3 feet. Dark, well-fed gromwell foliage carries a cloud of small, 1/2-inch flowers that radiate bright blue. The blossoms cover the plant in late spring and continue with sporadic blooms through the growing season.

Preparation at Planting

• One key to optimizing purple gromwell's health lies in preparing the planting site. Soil must have a neutral to acidic pH for the plant to access necessary nutrients. In alkaline soil, purple gromwell struggles. Incorporate acid-encouraging organic matter like peat moss into the soil before planting. Peat moss lowers soil pH, conditions soil and improves drainage. A well-drained, acidic site is essential for purple gromwell's health. With proper soil preparation, the plant needs little additional fertilizer to remain well fed. Hardy in U.S. Department of Agriculture plant hardiness zones 5 through 9, depending on variety, purple gromwell grows and flowers best in full-sun locations. In hot southern areas, cool shade is a must.

Ongoing Evaluation

• Well-nourished purple gromwell thrives to spread among the garden's contours. It blankets open areas, drapes across rocks and trails over garden edges. If foliage takes on a yellow cast, fertilization may be needed. Check first to be sure soil is not waterlogged or overly dry. Correct either situation before fertilizing with an acid-forming fertilizer. Cottonseed meal is a natural, acid-building product that provides slow-release nutrients to fuel acid-loving plants. Calculate the area your gromwell covers, and then broadcast cottonseed meal at a rate equivalent to 2 to 5 pounds per 1,000 square feet. Always wear gloves and protective clothing when working with fertilizers, even natural ones. Cottonseed meal can be applied as needed throughout the year. The nutrients are readily available when soils are warm.

Making a Move

• If your purple gromwell consistently looks unhealthy, a move to a more hospitable site may be needed. The plant is susceptible to root rot in poorly drained areas and to cold damage in overly exposed sites. If site preparation was lacking, it's not too late. One option is to lift the plant and prepare well-drained, acidic soil. Incorporate peat moss and cottonseed meal upfront. Transplanting or renovation should be done while the plant is dormant but the ground remains unfrozen. Keep as much soil as possible with each plant. Purple gromwell will not tolerate bare-root transplanting. In a fertile, acidic environment, healthy gromwell self-seeds and spreads freely to create a beautiful spring blanket of blue.