Plant library · Shrubs
Clethra alnifolia
Summersweet is a native perennial shrub that brings fragrant white flower spikes to the garden from midsummer into late summer. Growing about 6 feet tall and 5 feet wide, it has enough presence for the back or middle of a moist border without becoming a large screening shrub. Its flowers support pollinators, while deer resistance can make it useful along more exposed garden edges.
Use summersweet where the ground naturally stays moist: beside a downspout, at a pond edge, in a rain garden, or along the lower side of a gently draining bed. Set it back from paths so its mature branches do not narrow circulation, and place it where its late-season flowers can be noticed from a sitting area or entry route. It also suits grouped shrub borders and informal screens, especially in partly shaded sites.[1][2][3]
Space plants 4½ feet apart, center to center, for a connected planting that allows their roughly 5-foot mature widths to meet and soften into a continuous mass. For individual specimens, leave open ground around the full 5-foot footprint rather than tucking them tightly between walls, paths, or smaller shrubs. Keep a reachable edge on at least one side when planting in a deep border.
Give summersweet partial sun and consistently moist soil. It is well suited to acidic, organic-rich ground and can handle wet conditions, but a hot, dry planting pocket is a poor fit. In mixed borders, reserve the dampest zone for this shrub rather than placing it where nearby plants will compete for limited moisture.[1][2][3]
White flower spikes arrive from midsummer through late summer, extending interest after many earlier shrubs have finished. The foliage is late to emerge in spring, so leave room for early bulbs or low spring plants nearby without expecting the shrub to fill its space immediately. Flowers form on current-season growth, allowing shaping cuts in late winter or early spring.[1][2][3]
Allow room for the shrub to broaden over time. New shoots can arise from the root system and gradually form a thicket in favorable moist sites; remove them where a crisp specimen outline or clear path edge matters. Do not rely on it to solve a dry-shade problem, since dry conditions can also encourage spider mites.[1][2]
Editorial content updated 2026-07-20.