Weeds That Emit Odor
Wearing gloves for pulling weeds protects your hands from abrasion and scratches and also from the odors many weeds emit, especially when they're handled or crushed. Often the odors signal the presence of chemicals in the plants that are harmful if the plant is eaten. Sometimes the sap of smelly weeds can be irritating to your skin. A few weeds have pleasant smells, too.
Often growing in large groups, pineapple weed (Chamomilla suaveolens), a 6- to 12-inch-tall annual plant, has finely dissected foliage and pineapple-shaped yellow flowers. It releases a pleasant, sweet fragrance that resembles pineapple when it's walked on or otherwise crushed. Another small weed that resembles pineapple weed, mayweed chamomile (Anthemis cotula) differs in that it has small, white, daisylike flowers, more finely dissected leaves, and an unpleasant odor when crushed.
One of the largest-growing and smelliest weeds, datura (Datura spp.), also known as stinkweed, has two sources of odor. The leaves have an unpleasant smell and the white, trumpet-shaped flowers have a powerful, sweet fragrance. Depending on the species, the plants can reach 2 to 5 feet tall. They grow in waste areas and have round, spiny fruits. All plant parts are poisonous if eaten. Jimsonweed (Datura stramonium) is an annual plant that can reach 4 feet tall. Probably the tallest scented weed, fennel (Foeniculum vulgare) is a perennial growing from 4 to 10 feet tall. It has a licoricelike sweet odor when crushed. It grows in open, disturbed areas in USDA zones 4 through 9, often in dense stands. Native to the Mediterranean, fennel has feathery leaves and a broad, flat head of yellow flowers.
Distinctive because of the round, flat pods it bears, field pennycress (Thlaspi arvense) is a member of the mustard family, or Cruciferae, and is a winter or summer annual native to Europe. It grows to about 18 inches tall with clusters of small, white flowers at branch tips. It has an unpleasant smell, especially when crushed. The foliage is pungently flavored with a taste between garlic and mustard. Combining a strong odor with a sticky substance produced by glandular hairs on its leaves and stems, clammyweed (Polanisia dodecandra) has conspicuous, long, slender seed pods that follow the showy white flowers, which possess long, pink to purple stamens. This Mediterranean annual weed grows 1 to 3 feet tall.
Other Smelly Weeds
In areas with moist soils such as meadows, marsh edges and pools in floodplains, pennyroyal (Mentha pulegium) can be an invasive weed. The low-growing, spreading plant has a strong, minty odor. This European native grows in USDA zones 6 through 9. Violet, pink or blue flowers bloom in whorls along the upper stem areas. Also native to Europe, common yarrow (Achillea millefolium), which grows in USDA zones 3 through 9, has ferny-looking leaves and clusters of white or yellow flowers at stalk ends. The leaves have a pleasant, sagelike odor that lasts even in dried plants. Besides naturalizing into plant communities, such as salt marshes, grasslands, coastal bluffs and sand dunes, common yarrow is a weed in lawns and landscapes.
- UC Statewide IPM Online: Pineappleweed (Chamomilla Suaveolens)
- UC Statewide IPM Online: Mayweed Chamomile (Anthemis Cotula)
- UC Statewide IPM Online: Jimsonweed (Datura Stramonium)
- Cornell University: Fennel
- California Invasive Plant Council: Invasive Plants of California's Wildland: Foeniculum Vulgare
- Weeds of California and Other Western States, Volume 1; Joseph M. DiTomaso and Evelyn A. Healy
- Lady Bird Johnson Wildflower Center: Polanisia Dodecandra Ssp. Trachysperma
- California Invasive Plant Council: Invasive Plants of California's Wildland: Mentha Pulegium
- Plants for a Future: Mentha Pulegium - L.
- Missouri Botanical Garden: Achillea Millefolium
Cathryn Chaney has worked as a gardening writer since 2002. Her horticultural experience working in the nursery industry informs her garden articles, especially those dealing with arid landscaping and drought-tolerant gardening. Chaney also writes poetry, which has appears in "Woman's World" magazine and elsewhere. Chaney graduated from the University of Arizona in 1992 with a Bachelor of Arts in English.