florida Early Detection Network


Yellow hornpoppy, Sea poppy


Glaucium flavum Crantz


Poppy family


Glaucium flavum






Synonyms: Glaucium glaucium (L.) Karst.


Botanical Glossary

Glaucium flavum is a biennial or perennial that is 30-90 cm (1-3 ft.) in height. The leaves are firm, pubescent and glaucous. The basal leaves and the lowest cauline leaves have petioles while the other leaves are sessile. They are ovate to oblong, and are irregularly pinnatifid. The leaves are approximately 7-20 cm (3-8 in.) long and 2.5-5 cm (1-2 in.) wide. Their margins are deeply toothed. The flowers are axillary or terminal in their position. The yellow to almost orange petals are obovate in shape and 5-9 cm (2-3.5 in.) in diameter. At maturity the pedicel is thick and about 4 cm (1.5 in.) long. The seed capsule is sublinear and often curved, measuring 15-30 cm (6-12 in.) long by 5 mm (0.2 in.) wide. The capsule can be glabrous to scabrous and tipped with a persistent stigma. Page References Bailey 428, Fernald 680, Flora of North America 303, Gleason & Cronquist 67, Holmgren 64, Magee & Ahles 526, Newcomb 142, Peterson & McKenny 130. See reference section below for full citations.


Chelidonium majus (Celandine)*, Stylophorum diphyllum (Michx.) Nutt (Celandine poppy)**, Picture of S. diphyllum *See write-up in catalog of species, **Stylophorum diphyllum is not-native to New England, but is often cultivated.


Glaucium flavum reproduces by seeds that are dispersed mechanically. The seeds may also be dispersed by water, most likely during extreme high tide events. This plant has been spread in ballast and by escaping from garden plantings.


Glaucium flavum is native to the Black Sea region and also to Mediterranean Europe. It is a well-established ruderal species in central Europe. In New England it is currently limited to parts of coastal Massachusetts, Rhode Island and Connecticut (historically). It is found along the mid-Atlantic coast as far south as Virginia. It also occurs in Michigan, Oklahoma, Colorado and along the West coast of the United States.


Glaucium flavum was introduced to the coast of New England as early as the 17th century. Thomas Jefferson planted its seeds at Monticello in 1807. It is likely that it was repeatedly introduced, both through ballast waste and by horticultural planting. Robinson (1908) reported its presence in "waste places" of southeast New England. S.N. Sanford (1924) reported it as being present at a number of coastal sites in Rhode Island and Massachusetts (Rhodora, volume 26: pg. 127-128). Fernald (1950) described it as being found on "waste ground and sandy shores" from southeast Massachusetts and eastern Rhode Island to Michigan, south to Virginia and West Virginia.


Coastal Beach or Dune, Coastal Grassland, Edge, Open Disturbed Area, Roadside, Vacant Lot, Yard or Garden. Glaucium flavum can be found along the coast, above the high tide mark and below cliffs, banks and dunes. It is typically found in poor, sandy soils that are dry to well drained.


Glaucium flavum often fills a niche along the high tide zone in shoreline habitats. It has shown the ability to form dense stands that can crowd out native species that also share this niche.


Documentation required: A photograph of the flowers or the fruits. Best time for documentation: Spring, summer.


Integrated Taxonomic Information System Taxonomic information about the species

The PLANTS Database General information and map

Flora of North America Online Description, history of introduction and map


Andersen, R.N. 1968. Germination and Establishment of Weeds for Experimental Purposes. Weed Science Society of America Handbook. WSSA, Illinois.

Bailey, L. H. 1949. Manual of Cultivated Plants. Macmillan, New York.

Fernald, M.L. 1950. Gray's Manual of Botany 8th edition. American Book Company, New York.

Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. Volume #3. Oxford University Press

Flora of North America Association ed. 2000. Flora of North America vol. 3. Oxford University Press, Oxford, New York.

Gleason, H.A. 1952. The New Britton and Brown Illustrated Flora of the Northeastern United States and Adjacent Canada. Macmillan Publishing Co., Inc. New York

Gleason, H.A. and A.C. Cronquist. 1991. Manual of Vascular Plants of the Northeastern United States and Adjacent Canada. 2nd ed. New York Botanical Garden, Bronx, New York.

Holm, L.G., J.V. Pancho, J.P. Herberger, and D.L. Plucknett. 1979. A Geographical Atlas of World Weeds. John Wiley and Sons, New York, USA.

Holmgren, N.H. 1998. Illustrated Companion to Gleason and Cronquist's Manual. New York Botanical Garden, Bronx, New York.

Magee, D.W and H.E. Ahles. 1999. Flora of the Northeast. University of Massachusetts Press, Amherst.

Newcomb, N. 1977. Newcomb's Wildflower Guide. Little Brown, Boston.

Peterson, R.T. and M. McKenny. 1968. A field Guide to Wildflowers of Northeastern and North-central North America. Houghton Mifflin, Boston.

Thanos, C.A., K. Georghiou and F. Skarou. 1989. Glaucium flavum seed germination an ecophysiological approach. Annals of Botany London 63 (1): 121-130.

USDA, NRCS. 2001. The PLANTS Database, Version 3.1. (http://plants.usda.gov). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

Walmsley, C.A. and A. J. Davy. 1997. Germination characteristics of shingle beach species: effects of seed ageing and their implications for vegetation restoration. J. of Appl. Eco. 34(1): 131-142.

Walmsley, C.A. and A.J. Davy. 1997. The restoration of coastal shingle vegetation: effects of substrate composition on the establishment of seedlings. J. of Appl. Eco. 34(1): 143-153.