Kahili Ginger Care
The fast-growing kahili ginger (Hedychium gardnerianum) reaches a mature height of 6 feet. This herbaceous evergreen produces 12-inch long, ovate, verdant green leaves from rhizomes. Fragrant flower spikes consisting of individual yellow blooms sporting red stamens appear in the summer. Hardy in U.S. Department of Agriculture plant hardiness zones 9 through 11, kahili ginger plants require partial shade and moist, fertile, fast draining soils. With the proper care, these tropical perennials will add lushness to the landscape year after year.
Spread a 1- to 2-inch-deep layer of mulch with a rake around the kahili ginger plant each spring once new growth begins. Keep the mulch 4 inches away from the plant's base to avoid causing the stem to rot.
Water the plant when the top inch of soil becomes dry. Water the plant only in the morning hours, directing water from the garden hose straight to the ground. Avoid wetting the foliage as much as possible. Keep the soil moist but not soggy.
Fertilize the ginger plant with a 12-6-6 nitrogen, phosphorous, potassium slow-release fertilizer in the spring once it begins to produce new growth. Apply the fertilizer at a rate of 2 teaspoons per square foot of soil. Broadcast the fertilizer onto the soil in a 12-inch-wide band, 12 inches away from the plant's center. Rake the fertilizer into the top 3 inches of soil. Water the area thoroughly. Repeat the fertilizer application three months later.
Check the plant's leaves each time you water for the presence of aphids, whiteflies or spider mites. Wash the insects off the leaves with a strong stream of water. Spray large infestations with horticultural oil or insecticidal soap to eradicate the pests.
Cut back the plant once per year when it has finished flowering in the late summer or early fall. Cut through the base of each stem with a pair of pruning shears, 1 inch above ground level. Discard the foliage.
Divide the plant every three to four years, once its rhizomes become crowded. Dig around the perimeter of the plant with a shovel in the late fall or winter once plant growth slows and it enters its semi-dormant period. Dig down to a depth of 8 to 10 inches. Push the shovel's blade horizontally across the bottom of the root ball to cut it from the ground. Lift the plant from the ground with the shovel. Pull apart the plant's rhizomes, separating them into three or four clumps. Replant the clumps, spacing them 30 to 36 inches apart. Do not plant the clumps deeper than they were previously growing. Water the planted clumps immediately.