Prize-winning crossword

When all the answers are in place, the letters in the odd-numbered squares will spell out a tree genus, followed by two common names for the tree.

ACROSS

8 Common name for cynara, cultivated for its large, thistle-like flower heads (9) 9 Fighting force (4) 10 Fine-quality coffee (5) 11 Capital of Portugal (6) 12 Drink with small mouthfuls (3) 14 Go back (6) 15 Mainly nocturnal flying insect (4) 16 London Park (4) 19 Hovering songbird (4) 21 Misfortunes (4) 23 Sharp, stiff leaf of a fir tree (6) 25 Morning moisture (3) 27 Rhipsalidopsis, the ___ cactus (6) 28 Common name for ajuga (5) 29 Naked (4) 30 Plant commonly known as mullein (9)

DOWN

1 Yew genus (5) 2 Remains of a felled tree (5) 3 Hanging spike of ice (6) 4 ___ tuberosum, the potato (7) 5 Christopher John ___, horticulturist giving his name to a fast-growing cypress (7) 6 Fax in full (9) 7 Bring from abroad to sell (6) 13 and 22 down Group of US universities whose walls are traditionally covered in hedera? (3,6) 14 Common name of an Irish dog with a silky coat (3,6) 17 Cut a design in a hard surface (7) 18 Greenhouse plant also known as the Barberton daisy (7) 20 Shrub with bitter, strongscented leaves used in herbal medicine (3) 22 See 13 down (6) 24 Blockage caused by felled timber (6) 25 40-all in tennis (5) 26 Creatures cultivated by vermiculture (5)