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Vascular Plants of California
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Heracleum maximum


Higher Taxonomy
Family: Apiaceae (Umbelliferae)View DescriptionDichotomous Key
Habit: Annual to perennial herb [shrub, tree], generally from taproot. Stem: generally +- scapose, generally ribbed, hollow. Leaf: basal and generally cauline, generally alternate; stipules generally 0; petiole base generally sheathing stem; blade generally much dissected, occasionally compound. Inflorescence: umbel or head, simple or compound, generally peduncled; bracts present in involucres or 0; bractlets generally present in "involucels". Flower: many, small, generally bisexual (or some staminate), generally radial (or outer bilateral); calyx 0 or lobes 5, small; petals 5, free, generally ovate or spoon-shaped, generally incurved at tips, generally +- ephemeral; stamens 5; pistil 1, ovary inferior, 2-chambered, generally with a +- conic, persistent projection or platform at tip subtending 2 free styles. Fruit: 2 dry, 1-seeded halves (= mericarps), separating from each other but generally +- persistent to central axis; ribs on halves 5, 2 marginal, 3 to back; oil tubes 1--several per interval between ribs.
Genera In Family: 300 genera, 3000 species: +- worldwide, especially temperate; many cultivated for food or spice (e.g., Carum, caraway; Daucus; Petroselinum); Bupleurum lancifolium Hornem. is historical garden weed; some toxic (e.g., Conium). Note: Mature fruit generally critical in identification, shape given in outline. Hydrocotyle moved to Araliaceae, Orogenia moved to Lomatium, Sphenosciadium moved to Angelica. Petroselinum crispum (Mill.) A.W. Hill is a waif.
eFlora Treatment Author: Lincoln Constance & Margriet Wetherwax, except as noted
Scientific Editor: Douglas H. Goldman, Bruce G. Baldwin.
Genus: HeracleumView Description 

Common Name: HOGWEED
Habit: Perennial herb from taproot or clustered roots. Stem: stout, erect, generally branched, hollow. Leaf: blades oblong to round, ternately, pinnately, or palmately compound (simple), leaflets large, lobed or serrate; distal-most cauline generally reduced to large sheaths. Inflorescence: umbels compound, large, margins generally sterile; bracts 0--few, generally deciduous; bractlets generally present, persistent; rays, pedicels many, spreading-ascending. Flower: marginal bilateral, outer petals > others, 2-lobed; calyx lobes generally 0; petals wide, white, +- yellow. Fruit: oblong-ovate to round or obcordate, compressed front-to-back; ribs unequal, marginal thin-winged, veined near outer margin, others thread-like; oil tubes 1--2 per rib-interval, unequal in length; fruit axis divided to base. Seed: face flat.
Etymology: (Hercules, presumably from large stature of some species)
eFlora Treatment Author: Lincoln Constance & Margriet Wetherwax
Heracleum maximum W. Bartram
Habit: Plant 1--3 m, stout, tomentose, strong-scented. Leaf: round to reniform; petioles 1--4 dm, widely sheathing, distal sheaths enlarged, bladeless; blades 2--5 dm wide, ternate, leaflets 1--4 dm wide, ovate to round, cordate, lobed, coarsely serrate. Inflorescence: tomentose or long-hairy; peduncle 5--20 cm; rays 15--30, 5--10 cm, unequal; pedicels 8--20 mm. Flower: petals obovate, white. Fruit: 8--12 mm, obovate to obcordate, +- hairy. Chromosomes: 2n=22.
Ecology: Moist places, wooded or open; Elevation: < 2900 m. Bioregional Distribution: CA-FP, GB; Distribution Outside California: to Alaska, eastern United States, Arizona. Flowering Time: Apr--Jul Note: Only native Apiaceae sp. found from eastern to western North America.
Synonyms: Heracleum lanatum Michx.
Unabridged Note: Relationship to some Eurasian taxa unclear.
Jepson eFlora Author: Lincoln Constance & Margriet Wetherwax
Index of California Plant Names (ICPN; linked via the Jepson Online Interchange)

Previous taxon: Heracleum
Next taxon: Ligusticum

Botanical illustration including Heracleum maximumbotanical illustration including Heracleum maximum

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Citation for this treatment: Lincoln Constance & Margriet Wetherwax 2012, Heracleum maximum, in Jepson Flora Project (eds.) Jepson eFlora,, accessed on July 19, 2024.

Citation for the whole project: Jepson Flora Project (eds.) 2024, Jepson eFlora,, accessed on July 19, 2024.

Heracleum maximum
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©2015 Barry Breckling
Heracleum maximum
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©2008 Keir Morse
Heracleum maximum
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©2013 Neal Kramer
Heracleum maximum
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©2019 Neal Kramer
Heracleum maximum
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©2014 Neal Kramer

More photos of Heracleum maximum
in CalPhotos

Geographic subdivisions for Heracleum maximum:
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2. County and Jepson Region polygons can be turned off and on using the check boxes.
map of distribution 1

(Note: any qualifiers in the taxon distribution description, such as 'northern', 'southern', 'adjacent' etc., are not reflected in the map above, and in some cases indication of a taxon in a subdivision is based on a single collection or author-verified occurrence).


Data provided by the participants of the  Consortium of California Herbaria.

View all CCH records
All markers link to CCH specimen records. The original determination is shown in the popup window.
Blue markers indicate specimens that map to one of the expected Jepson geographic subdivisions (see left map). Purple markers indicate specimens collected from a garden, greenhouse, or other non-wild location.
Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues.

CCH collections by month Flowering-Fruiting Monthly Counts

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa, if there are more than 1 infraspecific taxon in CA.
Blue line denotes eFlora flowering time (fruiting time in some monocot genera).