Jack Dykinga / Rainbow over Long Canyon with fall coloured Cottonwood (Populus) trees against canyon walls, Burr Trail, Grand Staircase-Escalante National Monument, Utah, USA, October 2018.

Jack Dykinga / Waterfall over sandstone with cottonwood tree, Long Canyon , Burr Trail, Grand Staircase-Escalante National Monument, Utah, USA. October.

Jack Dykinga / Long Canyon on the historic Burr Trail, with Douglas fir (Pseudotsuga menziesii) against the 'varnished' canyon walls. Grand Staircase-Escalante National Monument, Utah, USA. October 2018.

Jack Dykinga / Long Canyon on the historic Burr Trail, with Douglas fir (Pseudotsuga menziesii) against the 'varnished' canyon walls with sheets of water flowing over the sandstone. Grand Staircase-Escalante...

Jouan Rius / View over Waterpocket fold and Burr Trail Road, Grand Staircase-Escalante National Monument, Utah, USA, April 2014.

Jouan Rius / View over Waterpocket fold and Burr Trail Road, Grand Staircase-Escalante National Monument, Utah, USA, March 2014.

Jeff Foott / Coast Redwood (Sequoia sempervirens) burr, Redwood National Park, California

Jeff Foott / Coast Redwood (Sequoia sempervirens) burr, Redwood National Park, California

Jeff Foott / Coast Redwood (Sequoia sempervirens) burr, Redwood National Park, California

Gary K. Smith / Beekeeper removing unproductive burr comb from Honey bee (Apis mellifera) hive.

Albert Lleal / Medick (Medicago sp) fruit covered in spines to enable animal dispersal, magnification 17x

Albert Lleal / Burdock (Arctium sp) entangled on the hair of a Domestic Dog (Canis familiaris), inspiration for the invention of Velcro

Carol Walker / Wild horses / Mustangs, close up of mane tangled up with burrs and grass seeds, South Dakota, USA

Gary K. Smith / English / Pendunculate Oak (Quercus robur) trunk showing swollen burr growths. Norfolk, England, April.

Gary K. Smith / English / Pendunculate Oak (Quercus robur) trunk showing swollen burr growths. Norfolk, England, April.

Jeff Vanuga / Circle Cliffs along the Burr Trail, Grand Staircase-Escalante National Monument, Utah, USA

David Welling / Burr Trail from Strike Valley Overlook with storm arising, Waterpocket Fold, Utah, USA

David Welling / Burr trail canyon and Henry mountains. Long Canyon, Utah, USA

Albert Lleal / Burdock (Arctium sp) inflorescence cross-section with hooked spines, magnification 26x

Albert Lleal / Blue Hound's Tongue (Cynoglossum creticum) hooked seed spines enabling animal dispersal of seeds, native to Mediterranean Basis a noxious pasture weed elsewhere, magnification 97x

Paul Harcourt Davies / Burr growth on trunk of an ancient European chestnut (Castanea sativa) tree, Il Sasseto, Lazio, Italy. April.

Claudio Contreras / Burr cucumber (Sicyos) vine growing over Blue echeveria (Echeveria secunda). Milpa Alta forest, outskirts of Mexico City, Mexico. August.

Paul Harcourt Davies / Sweet chestnut (Castanea sativa) burr split to reveal the chestnuts within, Umbria, Italy. November.

Jussi Murtosaari / Eurasian aspen (Populus tremula) tree trunk with swollen burr growth. Jyvaskyla, Finland. April.

Ernie Janes / Piri piri burr (Acaena novae-zelandiae) invasive species, Suffolk, England, UK, August.