Opuntia 3a NW Ocotillo, CA 130422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia 3b NW Ocotillo, CA 130422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia 4a Desert Botanical Garden, Phoenix, Arizona 130426 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia 4b Desert Botanical Garden, Phoenix, Arizona 130426 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia 4c Desert Botanical Garden, Phoenix, Arizona 130426 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia basilaris Bergianska 060514 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia basilaris var basilaris 8 Valencia, CA 130413 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia cf basilaris 1 NW Ocotillo, CA 130422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia cf basilaris 3 NW Ocotillo, CA 130422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia cymochila 1 Copenhagen Bot Garden 140625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia cymochila 2 Copenhagen Bot Garden 140625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia echios 1 Copenhagen Bot Garden 140625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia echios 3 Copenhagen Bot Garden 140625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia echios var gigantea 1 Copenhagen Bot Garden 140625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia echios var gigantea 2 Copenhagen Bot Garden 140625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia echios var gigantea 4 Copenhagen Bot Garden 140625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia engelmannii 1 W Tucson, Arizona 130424 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia engelmannii 4 W Tucson, Arizona 130424 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia ficus-indica 1 Masca, Tenerife 060417 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia ficus-indica 4 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia ficus-indica 5 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia ficus-indica 8 Barr. de Masca, Tenerife 160408 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia littoralis or O. oricola 3 Crystal Cove State Park, Newport Beach, CA 130414 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia littoralis or O. oricola 4 Crystal Cove State Park, Newport Beach, CA 130414 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia littoralis or O. oricola 5 Crystal Cove State Park, Newport Beach, CA 130414 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia littoralis or O. oricola 6 Crystal Cove State Park, Newport Beach, CA 130414 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia macrorhiza 2 Copenhagen Bot Garden 140625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia microdasys 2 Desert Botanical Garden, Phoenix, Arizona 130426 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia phaeacantha 5 Copenhagen Bot Garden 140625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia phaeacantha 6 Copenhagen Bot Garden 140625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia phaeacantha 7 Copenhagen Bot Garden 140625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia saxicola 1 Copenhagen Bot Garden 140625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia saxicola 2 Copenhagen Bot Garden 140625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia saxicola 3 Copenhagen Bot Garden 140625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia 2a Desert Botanical Garden, Phoenix, Arizona 130426 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia 2b Desert Botanical Garden, Phoenix, Arizona 130426 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia basilaris var basilaris 2 Valencia, CA 130413 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia basilaris var basilaris 4 Valencia, CA 130413 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia basilaris var treleasei 1 (cult) Wind Wolves Preserve, CA 130412 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia basilaris var treleasei 2 (cult) Wind Wolves Preserve, CA 130412 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia cf basilaris 2 NW Ocotillo, CA 130422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia echios 2 Copenhagen Bot Garden 140625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia echios var gigantea 3 Copenhagen Bot Garden 140625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia engelmannii 2 W Tucson, Arizona 130424 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia engelmannii 3 W Tucson, Arizona 130424 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia ficus-indica 2 Masca, Tenerife 060417 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia ficus-indica 3 Masca, Tenerife 060417 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia ficus-indica 6 Barr. de Masca, Tenerife 160408 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia ficus-indica 7 Barr. de Masca, Tenerife 160408 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia littoralis or O. oricola 1 Crystal Cove State Park, Newport Beach, CA 130414 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia littoralis or O. oricola 2 Crystal Cove State Park, Newport Beach, CA 130414 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia macrorhiza 1 Copenhagen Bot Garden 140625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia macrorhiza Desert Botanical Garden, Phoenix, Arizona 130426 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia microdasys 1 Desert Botanical Garden, Phoenix, Arizona 130426 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia microdasys 3 Desert Botanical Garden, Phoenix, Arizona 130426 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia oricola Desert Botanical Garden, Phoenix, Arizona 130426 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia phaeacantha 1 Desert Botanical Garden, Phoenix, Arizona 130426 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia phaeacantha 2 Desert Botanical Garden, Phoenix, Arizona 130426 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia phaeacantha 3 Copenhagen Bot Garden 140625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Opuntia phaeacantha 4 Copenhagen Bot Garden 140625 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).