Tidal Wave Purple Petunia is bathed in stunning purple trumpet-shaped flowers at the ends of the stems from mid spring to late summer. Its pointy leaves remain green in colour throughout the season. Tidal Wave Petunias can attain heights of 2 to 3 feet if spaced closely together, about 6 inches, and given support such as a trellis. If plants are spaced a foot apart, the mounded, hedge-like plants will reach 16 to 22 inches. Neither pinching nor pruning is needed for flowers all season.