Quercus 1 Storrs, Connecticut 900528 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 10a (cult) Rancagua, Chile 171111 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 10b (cult) Rancagua, Chile 171111 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 10c (cult) Rancagua, Chile 171111 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 10d (cult) Rancagua, Chile 171111 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 10e (cult) Rancagua, Chile 171111 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 10f (cult) Rancagua, Chile 171111 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 3b Crystal Cove State Park, Newport Beach, CA 130414 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 3c Crystal Cove State Park, Newport Beach, CA 130414 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 4b Rancho Santa Ana Botanic Garden, CA 130406 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 5a Ipsilou, Lesvos, Greece 130507 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 5b Ipsilou, Lesvos, Greece 130507 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 5c Ipsilou, Lesvos, Greece 130507 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 5d Ipsilou, Lesvos, Greece 130507 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 6b Kallonis Salt Pans, Lesvos, Greece 130509 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 6c Kallonis Salt Pans, Lesvos, Greece 130509 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 7a Julian, CA 130422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 7b Julian, CA 130422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 7c Julian, CA 130422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 8a Santa Margarita River, CA 130415 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 8c Santa Margarita River, CA 130415 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 8d Santa Margarita River, CA 130415 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 9a Julian, CA 130422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 9c Julian, CA 130422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus agrifolia 3 Triumphal Park, CA 130410 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus agrifolia 4 Triumphal Park, CA 130410 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus agrifolia 6 Oak Park, CA 130410 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus berberidifolia 1 Triumphal Park, CA 130410 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus berberidifolia 2 Triumphal Park, CA 130410 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus berberidifolia 3 Triumphal Park, CA 130410 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus brantii 1 Copenhagen Bot Garden 130913 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus brantii 2 Copenhagen Bot Garden 130913 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus brantii 3 Copenhagen Bot Garden 130913 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus broteroi 1 Río de la Miel, Los Alcornocales Natural Park, Andalucía Spain 220413 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus broteroi 2 Río de la Miel, Los Alcornocales Natural Park, Andalucía Spain 220413 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus broteroi 3 Río de la Miel, Los Alcornocales Natural Park, Andalucía Spain 220413 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus broteroi 4 Río de la Miel, Los Alcornocales Natural Park, Andalucía Spain 220413 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus broteroi 5 Río de la Miel, Los Alcornocales Natural Park, Andalucía Spain 220413 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus broteroi 6 Río de la Miel, Los Alcornocales Natural Park, Andalucía Spain 220413 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus canariensis 1 Río de la Miel, Los Alcornocales Natural Park, Andalucía Spain 220413 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus canariensis 2 Río de la Miel, Los Alcornocales Natural Park, Andalucía Spain 220413 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus canariensis 3 Río de la Miel, Los Alcornocales Natural Park, Andalucía Spain 220413 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus canariensis 4 Río de la Miel, Los Alcornocales Natural Park, Andalucía Spain 220413 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus cerris 1 Ålholm, Nysted, Lolland DK 130811 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus cerris 2 Ålholm, Nysted, Lolland DK 130811 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus cerris 4 Ålholm, Nysted, Lolland DK 130811 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus cf nigra 2 Storrs, Connecticut 900528 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus coccifera 1 Samos City, Samos, Greece 920504 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus coccifera 2 N of Gerakini, Greece 050525 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus coccifera 3 Sierra Blanca de Marbella, Andalucía Spain 220414 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus coccifera 4 Sierra Blanca de Marbella, Andalucía Spain 220414 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus coccifera 5 Sierra Blanca de Marbella, Andalucía Spain 220414 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus coccifera 6 Sierra Blanca de Marbella, Andalucía Spain 220414 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus dentata 1 Copenhagen Bot Garden 140515 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus dentata 2 Copenhagen Bot Garden 140515 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus dentata 3 Copenhagen Bot Garden 130913 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus dumosa 2 Torrey Pines, San Diego, CA 130418 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus dumosa 5 Torrey Pines, San Diego, CA 130418 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus dumosa 6 Torrey Pines, San Diego, CA 130418 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus dumosa 7 Torrey Pines, San Diego, CA 130418 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus faginea 1 south of Segovia SP 140505 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus faginea 2 south of Segovia SP 140505 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus faginea 3 south of Segovia SP 140505 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus faginea 4 south of Segovia SP 140505 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus frainetto 1 near Milea, old road to Grevena, N Greece 180628 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus frainetto Holomondas, Greece 050528 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus frainetto, Quercus cerris near Milea, old road to Grevena, N Greece 180628 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus ilex 2 south of Segovia SP 140505 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus ilex 3 south of Segovia SP 140505 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus ilex 4 N of Polygyros, Greece 050526 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus ilicifolia 1 Macedonia State Park, Connecticut 900606 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus ilicifolia 2 Macedonia State Park, Connecticut 900606 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus libani 1 Copenhagen Bot Garden 130913 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus libani 2 Copenhagen Bot Garden 130913 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus lobata 1 Gorman Hills, CA 130409 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus lobata 2 Gorman Hills, CA 130409 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus lobata 4 Gorman Hills, CA 130409 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus lobata 7 Gorman Hills, CA 130409 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus lobata 8 Oak Park, CA 130410 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus lobata 9 Oak Park, CA 130410 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus petraea 4 Skärva, Blekinge 160602 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus petraea 5 Skärva, Blekinge 160602 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus petraea 7 Skärva, Blekinge 160602 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus petraea Ogna S of Stavanger, Norway 050805 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus pyrenaica 2 Rio de Tieta, Toledo prov. SP 140506 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus pyrenaica 3 Rio de Tieta, Toledo prov. SP 140506 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus pyrenaica 4 Rio de Tieta, Toledo prov. SP 140506 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus robur 10 Lund Sk 130521 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus robur 11 Ålholm, Nysted, Lolland Sk 130811 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus robur 12 Ålholm, Nysted, Lolland Sk 130811 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus robur 13 Ålholm, Nysted, Lolland Sk 130811 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus robur 7 Lund Sk 130521 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus robur 8 Lund Sk 130521 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus robur 9 Lund Sk 130521 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus rotundifolia 3 (cult) Galileo, N Spain 180526 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus rotundifolia 4 (cult) Galileo, N Spain 180526 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus rubra 1 Lund Bot Garden 130906 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus rubra 2 Lund Bot Garden 130906 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus suber 1 near Alcántara SP 140507 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus suber 2 near Alcántara SP 140507 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus suber 3 near Alcántara SP 140507 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus suber 4 near Alcántara SP 140507 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus suber 5 near Alcántara SP 140507 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus suber 6 near Alcántara SP 140507 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus suber 8 Río de la Miel, Los Alcornocales Natural Park, Andalucía Spain 220413 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus suber 9 Río de la Miel, Los Alcornocales Natural Park, Andalucía Spain 220413 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus trojana 1 near Lake Mikri Prespa, N Greece 180629 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus trojana 2 near Lake Mikri Prespa, N Greece 180629 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 2 N of Polygyros (-Taxiarchis), Greece 050526 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 3a Crystal Cove State Park, Newport Beach, CA 130414 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 4a Rancho Santa Ana Botanic Garden, CA 130406 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 6a Kallonis Salt Pans, Lesvos, Greece 130509 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 8b Santa Margarita River, CA 130415 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus 9b Julian, CA 130422 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus agrifolia 1 Rancho Santa Ana Botanic Garden, CA 130406 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus agrifolia 2 Rancho Santa Ana Botanic Garden, CA 130406 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus agrifolia 5 Triumphal Park, CA 130410 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus broteroi 7 Río de la Miel, Los Alcornocales Natural Park, Andalucía Spain 220413 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus cerris 3 Ålholm, Nysted, Lolland DK 130811 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus cf nigra 1 New York Bot Garden 900505 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus cf pubescens Pantallica area, Sicily 190416 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus dumosa 1 Torrey Pines, San Diego, CA 130418 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus dumosa 3 Torrey Pines, San Diego, CA 130418 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus dumosa 4 Torrey Pines, San Diego, CA 130418 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus ilex 1 Lund Bot Garden 130528 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus ilex 5 N of Polygyros, Greece 050526 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus lobata 3 Gorman Hills, CA 130409 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus lobata 5 Gorman Hills, CA 130409 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus lobata 6 Gorman Hills, CA 130409 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus petraea 1 Skärva, Blekinge 160602 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus petraea 2 Skärva, Blekinge 160602 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus petraea 3 Skärva, Blekinge 160602 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus petraea 6 Skärva, Blekinge 160602 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus petraea x robur Gullarp, Osby, Skåne 810723 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus prinus Macedonia State Park, Connecticut 900606 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus pyrenaica 1 Rio de Tieta, Toledo prov. SP 140506 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus robur 1 Lund Sk 130521 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus robur 2 Lund Sk 130521 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus robur 3 Lund Sk 130521 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus robur 4 Lund Sk 130521 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus robur 5 Lund Sk 130521 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus robur 6 Lund Sk 130521 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus rotundifolia 1 (cult) Galileo, N Spain 180526 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus rotundifolia 2 (cult) Galileo, N Spain 180526 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus suber 10 Río de la Miel, Los Alcornocales Natural Park, Andalucía Spain 220413 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).

Quercus suber 7 near Alcántara SP 140507 - Photo: Jan Thomas Johansson (© 2014 Jan Thomas Johansson).