Plant alyssum in well-drained soil after spring's last frost. Space plants 8 inches apart. If sowing seeds, don't cover them with soil, as they depend on light exposure for germination. Seeds also require temperatures between 65 and 75 degrees Fahrenheit.
Mix 2 tbsp. of a 10-52-17 fertilizer with 1 gallon of water. Apply 1 cup of this high-phosphorous formula to each alyssum seedling at transplanting to promote quick root development.
Irrigate alyssum flowers infrequently, as they have a low water requirement. Water them when the soil surface feels dry to the touch. At that time, apply 1 inch of water in one single soaking session.
Prune alyssum flowers when they go to seed in mid-summer to encourage a second batch of blooms. Mow them if the plants are in an area without obstructions. If they're planted among rocks, for instance, cut the dead flowers with shears.
Prepare for a new generation of alyssum flowers come spring. At the end of the season, allow the dead plants to stay in the ground as insulation for the self-sown seeds and tender seedlings. Pull the dead alyssum out of the ground after the last frost in spring to expose newly germinated plants.