Heracleum maximum Bartram
Heracleum lanatum Michx.
Heracleum sphondylium L. ssp. montanum (Schleich. ex Gaudin) Briq.
Heracleum sphondylium L. var. lanatum (Michx.) Dorn
Cow Parsnip, Indian Celery, Pushki
Cow parsnip, named because cows like it, is a North American native, common except in the Gulf Coast states.
Identification: Plants reach 6½' (2 m) in height. Stems are thick, grooved, hollow, hairy, and often reddish. Leaves are up to 16" (40 cm) across, split into sharp lobes that vaguely resemble maple leaves, with a disagreeable odor. Flowers appear in large white compound umbels about 8" (20 cm) in size. Individual flowers have five petals of inconsistent size. There are several other members of the carrot family with similar-appearing flowerheads, including another very common plant, Queen Anne’s lace. Fruits are flat, green, egg- or heart-shaped, ⅜-½" (9.5-12 mm) × ¼-⅜" (6.3-9.5 mm). They smell like parsley.
Here are some similar-appearing species:
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|Plant||Extremely large: 6½-16' (2-5 m) tall, sometimes reaching 23' (7 m). Poisonous : causes phytophotodermatitis.||Up to 6½' (2 m) in height. Poisonous : causes phytophotodermatitis.||Grows to 3’ in height. Plant smells like carrots.|
|Flowers||White flowers form flat-topped compound umbels (flowerheads) up to 30" (76 cm) in diameter.||Large white compound umbels about 8" (20 cm) in size. Individual flowers have five petals of inconsistent size.||Pale pink before opening. When open, forms an umbrella-shaped flower cluster up to 3” across, composed of tiny 5-petaled flowers.|
|Leaves||Leaves are up to 5' (1.5 m) across, extensively divided into sharp-tipped sections.||Up to 16" (40 cm) across, split into sharp lobes that vaguely resemble maple leaves, with a disagreeable odor.||Compound leaves are deeply divided and subdivided.|
|Stem||Hollow stems are 1-4" (3-10 cm) in diameter, with deep purple raised blotches containing white hairs.||Thick, grooved, hollow, hairy, and often reddish.||Fine hairs on stems and leaves.|
|Seeds||Each seed is up to ¼" (8.3 mm) long.|
|Fruit||Flat, green, egg- or heart-shaped, ⅜-½" (9.5-12 mm) × ¼-⅜" (6.3-9.5 mm).|
|Habitats||Rich, moist soils in ditches, stream banks, vacant farmland, and fence and tree lines||Moist, shady mountain woodlands, streambeds|
Medical: Poisonous These plants contain furocoumarins in their sap, a defense against fungal attack. It happens that these chemicals cause phytophotodermatitis in people—that is, severe sensitivity to sunlight. If you come in contact with the plant, then are exposed to long wave ultraviolet light (sunlight), the dermatitis may develop. The exposed skin becomes bright or dark red, developing large blisters. The effects resemble chemical burns, and can leave permanent discoloration or scarring. Temporary or permanent blindness can result from eye exposure.
Heracleum maximum at Southeastern Arizona Wildflowers and the Plants of the Sonoran Desert
Heracleum maximum on the USDA Plants Database
Heracleum maximum on Wikipedia
Heracleum maximum at the Lady Bird Johnson Wildflower Center
Heracleum maximum on Montana Plant Life
Heracleum maximum description by Thomas H. Kent, last updated 12 Oct 2018.