Plant in full sun in a decently well-drained soil and give occasional to only a little water – notably hard to grow in heavy clay soils where it rots out in wet winter conditions. Cold hardy to below 0° F and useful in gardens in USDA Zones 6 and above. This plant is perennial but is often listed as a biennial because of its typically short lifespan; however, it often lasts more than two years and, unlike a biennial, blooms the first year from seed and then reblooms in subsequent years, prompting some to call this plant a "triennial". The reseeding nature of this plant perpetuates its life in the garden but has also caused it to be considered a weed species in some areas. Some also find this plant a bit disorderly but it is a great addition to the natural garden where its attractive glaucous foliage alone compliments California native and other mediterranean climate plants and a great plant for gardens by the sea though notably can escape the garden in these sandy conditions, so not recommended in areas adjacent to wildlands.

Glaucium flavum is found naturally from coastal northern Europe, the British Isles and around the Mediterranean in Europe, North Africa and Southwest Asia, in a wide range of habitats near the ocean or in otherwise saline or lean soils. The plant contains the alkaloid glaucine in its yellow sap and all parts, particularly the roots, are considered poisonous if ingested. The name for the genus was first described by the Scottish botanist, Philip Miller in 1754, and comes from Latin word 'glaucus' which comes from the Greek word 'glaukos' meaning "gray-green" in reference to the color of the foliage. The specific epithet 'flavum' given by the Austrian botanist Heinrich von Crantz comes from the Latin word 'flavus' meaning "golden yellow", "reddish yellow", "flaxen" or "blonde" in reference to the flower color. The predominant common name comes from the narrow horn-like seed capsules that are used in dried floral arrangements. It is also called the Sea Poppy for its preference to habitats near the ocean and some refer to it as the Rhodes Poppy because they have seen it growing on the Isle of Rhodes.

We have grown this attractive and interesting perennial since 2012 and it has long been grown in California. Peter Reidel included it in his 1957 Plants for Extra-tropical Regions with the note that it was grown infrequently in Santa Barbara Gardens where it treated as a very showy annual. It made it into the 1961 Sunset Western Garden Book with the comment "Striking with other gray plants, interesting with succulents". In the Winter 1984 issue of Pacific Horticulture in an article about a tour group visit to Santa Barbara titled "Spring in Santa Barbara" the garden author Phil Chandler wrote about a beach front property that has a "sea of horned poppy, Glaucium flavum, long ago naturalized from seed carried home from the island of Rhodes." While this plant has been recorded as seeding into the wild along the east coast of the US, and is a declared noxious weed in the State of Massachusetts, it has had no such standing in California but in July 2024 Glaucium flavum was identified growing in sandy soil near Point Mugu State Park in Ventura County, California and it is likely that this plant is on the way to becoming a declared noxious weed in our state. 

This information about Glaucium flavum displayed is based on research conducted in our horticultural library and from reliable online resources. We also will relate observations made about it as it grows in our nursery gardens and other gardens we have visited, as well how the crops have performed in containers in our nursery field. We will also incorporate comments that we receive from others and we welcome hearing from anyone with additional information, particularly if they can share any cultural information that would aid others in growing it.