Nigel Cattlin / Crown imperial (Fritillaria imperialis) flower head, close up.

Nigel Cattlin / Beet armyworm / Small mottled willow (Spodoptera exigua) moth on Cotton (Gossypium sp) flower bracts.

Heather Angel / Thorowax (Bupleurum rotundifolium) umbel with green bracts, backlit in studio.

Heather Angel / Masterwort (Astrantia sp) with pink bracts and tiny florets. Cultivated in garden, Surrey, England, UK. Controlled conditions.

Heather Angel / Monarch butterflies (Danaus plexippus), three nectaring on Poinsettia (Euphorbia pulcherrima), resting on red bracts. In butterfly house, Xishuangbanna, Yunnan Province, China.

Heather Angel / Alexander's rhubarb (Rheum alexandrae) and Dwarf purple rhododendron (Rhododendron impeditum) in wet valley. Large bracts on rhubarb protect tiny flowers from UV rays. Near Lake Kangding Xian Cuo,...

Heather Angel / Handkerchief / Dove tree (Davidia involucrata), male inflorescence enclosed by bracts which act as an umbrella to prevent rain spoiling pollen. Endemic to Sichuan, north west Yunnan, Guizhou and Hubei...

Heather Angel / Alexander's rhubarb (Rheum alexandrae) and Dwarf purple rhododendron (Rhododendron impeditum) in wet valley with low cloud. Large bracts on rhubarb protect tiny flowers from UV light. Near Lake Ka...

Chris Mattison / King protea (Protea cynaroides) showing involucral bracts around the flower bud, native to South Africa but growing in the Botanical Gardens, La Gomera, Canary Islands

Pascal Pittorino / Bougainvillea(Bougainvillea glabra) with colourful leaf bracts, in botanic garden, Var, France, Provence, July.

Nick Upton / Lesser burdock (Arctium minus) with red stems and purple tinged spiny bracts on the flowerheads, about to flower in rough grassland near the coast, Gower Penisula, Wales, UK, July.

Kerstin Hinze / Poinsettia (Euphorbia pulcherrima) red bracts surrounding flowers