Delightful with their lemony fragrance, the narrow green leaves of the lemon verbena (Aloysia triphylla), can be used to flavor food dishes, scent potpourri, and make perfume. A gangly shrub native to southern South America, it can be grown in a container and as a houseplant. In late spring or summer, the branch tips bear slender clusters of tiny lavender- to white-colored blossoms.
Lemon verbena is native to the rocky, well-drained loams of northern Argentina and northeastern Chile in South America.
Lemon verbena is a bushy, upright-growing shrub that reaches heights up to 10 feet, and a potential spread of 8 to 10 feet. Full sun exposures ensure a more compact shape. Often gardeners frequently tip prune leggy stems and allow regrowth to create a more multi-branched, bushy specimen.
Leaves are narrow and lance-shaped and smell of lemon citrus when bruised. Each blade is a bright green in color and has a rough texture. On the stems and branches, the leaves are arranged in opposite pairs or in a simple whorl of three, hence the botanical name of "triphylla".
For finest fragrance, harvest and/or dry leaves in early to midsummer before flowering occurs.
Lemon verbena is a deciduous shrub, losing its leaves in the autumn or winter chill or droughts in regions with mild, but frosty winters. In warm, tropical regions the plant can be fully evergreen.
Depending on the mildness of the climate, stem tips are filled with flowers in late spring to late summer. The flowers are tiny and lavender to white in color and borne in short, slender spikes atop the branches, called panicles. The flowers are fragrant but are not overly ornamental except when viewed up close.
Plant lemon verbena in a well-draining garden loam soil that can be slightly gritty or rocky in texture. Adaptable to a wide array of soils, it excels in those that have an alkaline pH (7.0 to 8.0). For best plant shape, foliage quality and flowering, place it in full sun exposures, receiving at least 6 to 8 hours of direct sunlight each day.
Lemon verbena is winter hardy in USDA Plant Hardiness Zones 8, 9, 10 and 11. Plants may be grown in a warm microclimate and mulched heavily in winter in Zones 6 and 7. Elsewhere it is grown as a summer annual herb. It may be grown in a container and overwintered indoors and relocated outdoors when there is no danger of frost.