Prize-winning crossword

When all the answers are in place the letters in the even-numbered squares will spell out the name of a well-known nursery and garden and the surname of the family that established it.

ACROSS

5 Plant of the cabbage family sometimes used in salads (5) 8 Perennial also known as golden rod (8) 9 31 across prepared from a type of poppy (5) 10 Fruit of the blackthorn (4) 11 Capital of Egypt (5) 12 Mischievous spirit (3) 15 ‘___ Star’, very dark variety of agapanthus? (8) 18 Sound that 28 across make (4) 20 Maple genus (4) 21 Aunt or uncle, for example (8) 22 10 across ___, comic book hero (3) 27 Take it easy (5) 28 14 down birds of prey (9) 30 Giant and hunter of Greek mythology (5) 31 Drug that induces drowsiness (8) 32 Painting on a wall (5)

DOWN

1 Natural planting medium (4) 2 Carmen composer (5) 3 Tree of the genus larix (5) 4 Shrub commonly known as the rose-acacia (7) 5 Club-shaped American squash with a warty skin (9) 6 Way out (4) 7 Japanese wrestling (4) 10 Chlorophytum comosum, the ___ plant (6) 13 and 19 down Singer whose debut solo single was In the Air

Tonight in 1981 (4,7) 14 Active at night (9) 16 Harmful micro-organism (4) 17 Lawn game (6) 19 See 13 down 23 Crowd actor (5) 24 Chest (5) 25 Plant’s underground storage organ (4) 26 One who tells untruths… (4) 29 … and its anagram, an animal’s den (4)