The basal leaves of young plants have similarities to : Prickly Saltwort.
Some similarities to : Greater Celandine in that it has large yellow flowers and glaucous green foliage, but Yellow-horned Poppy grows next the sea.
The leaves are glaucous-green and wavy and similar to those of another seaside plant Sea Kale but that has white flowers and almost spherical seed pods.
Uniquely identifiable characteristics : No other plant quite looks like this one.
Distinguishing Feature : Grows on shingle beaches above low tide, is greyish green with yellow poppy-like flowers, and preposterously long curved seed pods (the 'horns').
The large yellow flowers are reminiscent of those of Courgette (Cucurbita pep) but those have but five petals that are pointed.
In their first year, the plant just has a basal rosette of hairy greyish-green pinnately-lobed leaves. In the second year the plant grows further, producing encompassing glaucous greyish green leaves without hairs, and flowers in the form of a yellow poppy. The flower, later in the year, sprouts an enormously long seed pod from the centre, which when ripened, splits lengthways to yield the seeds.
It is salt-tolerant, and grows almost exclusively on shingle beaches washed by the high tide, hardly ever on sand. The stems, if broken, ooze a milky yellow sap. Like all poppies, it is toxic.
The coastal shingle plants Sea Kale (Crambe maritima)
Yellow-hormed Poppy (Glaucium flavum) and Rock Samphire (Crithmum maritimum) are thermophilous, growing well and increasing in numbers with warmer summers.
It contains the aporphine group alkaloid
Glaucine which is the main alkaloid within Yellow-horned Poppy but which is also found in several other Poppy species and has bronchodilatory and anti-inflammatory effects. Glaucine is used medicinally in some countries but one of the side effects are chromatic hallucinations. This makes it a target as a recreational drug. Several other minor alkaloids have been found in this plant which are thought to be produced from Glaucine by oxidation processes within the plant. Such alkaloids as Pontevedrine, O-MethylAtheroline and Sinoacutine plus the recently discovered aporphine alkaloid
Glauvine. Barberry has a greater collection of Aporphine group alkaloids.
[Glaucine should not be confused with the Amino Acid
The above are oxidation products of Glaucine, with the possible exception of Sinoacutine, which has a re-arranged nitrogen-containing ring and is possibly the more toxic because it is polycyclic and spans another ring making for a forced 3-dimensional structure. All four have at least one ketone (=O) group.