Alliaria petiolata aka Garlic Mustard

Alliaria petiolata, or garlic mustard, belongs to the mustard family. Its native range spans Europe, central Asia, northern Myanmar, and northwest Africa. It is native to Britain and Ireland. This herb grows fast and most often lives two years. It reached North America as a food plant in 1860. It now invades North Carolina and many other states.

Garden plants reach about 1.6–3.3 feet [0.5–1 metre] tall. They spread about 0.3–1.6 feet [0.1–0.5 metres] wide. First-year plants form low clumps of round or heart-shaped leaves. The green leaves have coarse teeth along their edges. In year two, the stem leaves become more triangular. They grow in turn along the stem rather than opposite pairs. Crushed leaves give off a strong garlic smell. Stems often lack branches and may bear some hairs. The foliage can stay green through winter.

Small white flowers open in spring during the second year. Each flower has four petals arranged like a cross. Flowers crowd near the tips of narrow racemes. These clusters lengthen as the seed pods form. The slim pods start green, then turn grey-brown. They split in midsummer and release shiny black seeds. One plant can shed hundreds of seeds and form colonies. This spread can displace native wildflowers that bloom in spring.

Garlic mustard grows in damp hedges and along woodland edges. It suits partial or full shade and rich, moist soil. RHS recommends soil that drains well despite staying moist. It grows in sand, loam, clay, and chalk-based soils. It accepts acid, neutral, and alkaline conditions. RHS rates its cold tolerance as H6. NC State lists USDA zones 6a through 8b. Seeds need a long cold spell to break dormancy. RHS suggests autumn sowing when planting seeds in place.

In its native setting, it has value in wildlife gardens. It feeds orange-tip and green-veined-white butterflies, though caterpillars can damage leaves. RHS reports few disease problems and no need for pruning. Its invasive spread makes it a poor choice where introduced. NC State advises removal there and warns against composting pulled plants. The leaves add garlic and mustard notes to food. Young leaves suit salads, sauces, or cooked dishes. Roots can flavour soups, while seeds serve as seasoning. Flowers and young pods are also edible. PFAF reports no known hazards, rather than proof of complete safety. The whole plant can also yield a yellow dye.