Position gomphrena plants in full sunlight. Although the plants tolerate partial shade, full sun makes for more vibrant blossoms. These bedding flowers aren’t picky about soil type, but it’s best to plant them in well-drained soil during spring. Gomphrena prefers soil with a pH range of about 5.8 to 6.2 and needs about 12 to 18 inches of space.
Fertilize the plant with a balanced, slow-release fertilizer with an N-P-K ratio such as 14-14-14 at planting. Add a water-soluble fertilizer according to the instructions on the label once every few weeks.
Water the gomphrena just enough to keep its root zone saturated. Add water when the topsoil is dry to the touch. Although this plant tolerates the warm weather of the Bay Area well, it flourishes when kept on a regular watering schedule.
Spread a thin layer – about 2 inches – of organic mulch in the gomphrena’s bed during summer.
Trim the gomphrena in early spring. Pinch off branch tips to encourage a bushier exterior and pinch off wilted blooms at the stem.
Remove any plants affected by viral disease from the flower bed to prevent spreading. Dig affected plants out by the root, removing the root system completely.
Spray gomphrena with silicone oil NMI-500 or NMI-15 to prevent cutworms, aphids and beetles.