Fig. 1

Phenotypic evaluation of three wild Chinese and seven European thyme (Thymus) species. a Plant types. i T. rotundifolius (Tr); ii T. vulgaris ‘Elsbeth’ (Tve); iii T. thracicus (Tt); iv T. vulgaris ‘Fragrantissimus’ (Tvf); v T. serpyllum ‘Aureus’ (Ts); vi T. guberlinesis (Tg); vii T. longicaulis (Tl); viii T. quinquecostatus (Tq); ix T. quinquecostatus var. przewalskii (Tqp); x T. mongolicus (Tm). b Floral organ arrangement. i T. rotundifolius (Tr); ii T. vulgaris ‘Elsbeth’ (Tve); iii T. thracicus (Tt); iv T. vulgaris ‘Fragrantissimus’ (Tvf); v T. serpyllum ‘Aureus’ (Ts); vi T. guberlinesis (Tg); vii T. longicaulis (Tl); viii T. quinquecostatus (Tq); ix T. quinquecostatus var. przewalskii (Tqp); x T. mongolicus (Tm). Scale bars = 1 mm. c Glandular trichomes on the adaxial and abaxial surface of leaves. i Adaxial; ii Abaxial; iii Glandular trichomes on the abaxial surface. d Images of thyme essential oil. e Glandular trichome number on the adaxial and abaxial surfaces of leaves. f Essential oil (EO) yield