Mexican petunias are vibrant, showy plants that are drought and heat resistant. They add easy color to a sunny spot but also do well in shade. They grow well in containers, and their aggressive growth makes them perfect for filling in bare spots in your garden. Depending upon your climate these shrubs can be grown as hardy perennials or as summer annuals. Once established they will deliver constant blooms from May through November. Mexican petunia grows and blooms best in full sun or partial shade. This sun-loving perennial likes rich, slightly moist soil so mulch the plants to maintain consistent soil conditions, especially during hot, dry weather. In the North, Mexican petunia can be grown as an annual flower. Mexican petunia can become a fast spreader -- so plant it where you can control its spread. Handsome narrow, dark green foliage covers the tall stems, topped with pink petunia-like flowers. Thrives in a variety of conditions. Plant toward the rear of a border or as the centerpiece of a mixed container. Herbaceous perennial. Follow a regular watering schedule during the first growing season to establish a deep, extensive root system. For a neat appearance, remove old foliage before new leaves emerge. Divide clumps every 2 to 3 years in early spring.