Possible Clues:

• Prickly pear and saguaro
• Jersey etc must be worn by order of Parliament in plants
• Arctic's not right for their cultivation
• Spiky desert plants in plural
• One after prestige when he's away exhibiting plants
• They often break Wile E.'s falls
• They're hardly spineless
• They may be pointed out in the desert
• Before start of play, cheerleader gets flowers
• Prickly pear and barrel