Spiraea alba aka White Meadowsweet

Spiraea alba, or meadowsweet, belongs to the rose family. This deciduous shrub comes from eastern and midwestern North America. It grows in wet meadows, marshes, and low woods. Wild plants also grow beside streams, lakes, and river bottoms. The species is endangered in Missouri. This local status does not establish its global conservation status.

Garden plants grow about 3–4 feet (0.9–1.2 m) tall and wide. RHS gives an upper size of about 5 feet (1.5 m). The shrub grows upright and can form dense thickets through suckers. Its many slender stems give it a fine texture. Young branches are green and lack hairs. Older wood turns brown, sometimes with red or yellow tones. Narrow leaves grow in an alternate pattern along the stems. Their edges have sharp teeth, and their undersides are paler. The green leaves turn yellow before falling in autumn.

Small, scented flowers form cone-shaped panicles at the stem tips. The blooms are white, though some may be pale pink. Each flower has five petals and many long stamens. Flowering runs from June to August, sometimes into September. Blooms open from the top of each cluster downward. Brown fruits ripen in autumn, with September noted by Missouri Botanical Garden. Each fruit has five follicles that split as they dry. These release seeds but add little to the garden display.

Give this shrub full sun for its best growth. It also grows in part shade. It accepts clay, loam, and sand with acid or neutral pH. Keep the soil moist; do not let it dry out. Wet and boggy sites suit it, and it tolerates poor drainage. Heat and dry soil can impair its growth. Sources rate it for USDA zones 3–7 and UK hardiness H6. It needs little upkeep and grows at a moderate pace. Removing old flower clusters can encourage more blooms.

Use meadowsweet beside ponds, in rain gardens, or in damp borders. It also suits hedges and cottage gardens with steady watering. Its flowers attract butterflies and provide nectar for other pollinators. Spring azure caterpillars use it as a host plant. Deer tend to leave it alone. Serious pest problems are rare, but aphids and scale may occur. Leaf spots, powdery mildew, fireblight, rots, and honey fungus are possible. PFAF records leaf tea and a traditional tonic use. It reports no known hazards, rather than proven safety.