Essence of a tea tree

Tea tree or Ti-tree is a popular name that has been applied to a number of different, unrelated plants:
Camellia sinensis (aka Thea sinensis), from which black, green, oolong and white tea are all obtained.
Melaleuca alternifolia from which tea tree oil is obtained, in the family Myrtaceae.
Leptospermum, also in the family Myrtaceae; notably
Leptospermum scoparium (Manuka) in New Zealand and southeast Australia.
Leptospermum laevigatum, known as the Coastal Tea Tree and the Australian Tea Tree
Kanuka (Kunzea ericoides) also in New Zealand.
Boxthorn or Lycium in the family Solanaceae, notably
Duke of Argyll's Tea Tree (Lycium barbarum), also known as Wolfberry or Matrimony Vine.
Ti (plant), Cordyline fruticosa, in the family Laxmanniaceae, formerly treated in the family Agavaceae.