Possible Clues:

• Matted growth
• Parasitic plant
• Supermodel who gathers no pounds?
• Some spores, all grown up
• Freebooter who used to frequent English/Scottish border in 17th century
• Pat, who shared her brother's love of horse power
• Type of plant growing in damp places
• Pat, who excelled in two types of horse power and also showed sister power!
• Stirling . . . ., Kate . . . .
• Pat, who enjoyed double horse power