Nemesia is a decorative flowering plant appreciated for its delicate, snapdragon-like blossoms and sweet fragrance. These compact plants are frequently used to create dense bursts of color in window boxes, patio containers, and garden borders. Nemesia produces continuous flowers throughout the growing season, making it a favored bedding plant. Cultivars are available in a vibrant spectrum of colors, including blues, pinks, reds, and whites.
Determining Nemesia’s Life Cycle
The life cycle of Nemesia depends entirely on the climate in which it is grown. Nemesia species are native to South Africa, where they thrive as tender perennials and can live for several years. This perennial habit is maintained only in regions that do not experience freezing temperatures, typically USDA Plant Hardiness Zones 9 through 11.
In these warmer zones, the plants remain in the ground year-round. In temperate regions with cold winters, the plant lacks the cold tolerance to survive below-freezing temperatures and is cultivated as an annual. Gardeners in Zones 8 and below treat Nemesia as a seasonal display, replacing the plant each spring after the danger of frost has passed. The genus Nemesia also contains different species, such as N. strumosa, which is a true annual, while N. caerulea is recognized as a tender perennial.
Care for Nemesia Grown as Annuals
Nemesia is planted in spring as a seasonal annual once the soil has warmed and the risk of late frost is over. These plants perform best in full sun, requiring a minimum of six to eight hours of direct sunlight daily. In areas with intense summer heat, the plant benefits from afternoon shade to prevent wilting or dormancy.
Nemesia requires organically rich, well-draining soil to prevent root rot. Consistent soil moisture is important for continuous flowering; water potted plants and garden beds when the top one to two inches of soil feel dry. Encouraging a bushier habit involves pinching out the growing tips of young plants. Removing spent flowers, known as deadheading, redirects the plant’s energy from seed production into creating new buds, extending the display into the fall.
Overwintering and Perennial Maintenance
Maintaining Nemesia as a perennial outside of its hardy range requires specific measures to protect it from cold temperatures. In marginally hardy areas, such as USDA Zone 8, in-ground plants can survive by applying a heavy layer of organic mulch over the root zone. This insulation helps stabilize soil temperature and shields the roots from sudden freezes, though survival is not guaranteed.
A more reliable method is to overwinter container-grown Nemesia indoors in a protected, frost-free environment. Before the first expected frost, lightly trim the plant and move it to a cool location, such as a garage or unheated conservatory, where temperatures remain above 45°F. During this dormancy, watering must be significantly reduced, providing only enough water to prevent the soil from completely drying out while avoiding rot. The plant can be pruned back substantially in late winter or early spring before being reintroduced to the garden after the last frost date.