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Rockrose
Helianthemum nummularium
γγ³γγγγ
A perennial herb to subshrub native to the Mediterranean coast, rarely found as a naturalized plant in Japan. Named for its yellow flowers that open only in the morning and close (half-day flower). Prefers dry grasslands on limestone.
Identification Points
- βYellow 5-petaled flowers open only in the morning (ephemeral)
- βLeaves opposite, small, with abundant stellate hairs on stems and leaves
- βPetals fall soon after blooming
Habitat
Dry grasslands and limestone areas (naturalized)
Season
MayβJuly (flowers)
Morphological TraitsAI-estimated, needs verification
Growth form
Herb
Leaf arrangement
Opposite
Flower color
Yellow
Leaf type
Simple
Petal count
6 petals
Petal fusion
Fused
Leaf dissection
Undivided
Flower symmetry
Actinomorphic
Ovary position
Superior
Plant sex
Hermaphrodite
Phylogenetic Positionγγ³γγγγη§ β
Phylogenetic Position
Angiosperms > Eudicots > Core eudicots > Malvales > Cistaceae
Divergence Era
Paleogene (ca. 55 million years ago)
Evolution Notes
Cistaceae belongs to Malvales; the ephemeral flowers that open and close rapidly are adapted for pollination mutualism with insects active during short time windows.
View on evolution timeline βSources & References
AI-generated, needs verification