Possible Clues:

• Succulents planted in midst of hectic activity
• Nesting places for elf owls
• Arizona sights
• Their sharp points scratch this, at intervals?
• Saguaro National Park sights
• Spiny specimens
• Frequent sights in Road Runner cartoons
• Some drought-resistant plants
• They're thorny in deserts
• Landscapers may find them hard to handle