Mexican Heather is a great addition to summer gardens when you need some fresh green foliage dotted with long-lasting color. 'Allyson' can grow from 12 to 24 inches tall and wide, all the while maintaining a neat, mounding appearance lavishly sprinkled with tiny purple flowers. Fine for sunny borders on its own, or used as a filler in container planters and hanging baskets, cuphea is a low-maintenance summer annual that keeps its good looks right up until frost.