From our perspective, the answer to whether we come back is fundamentally tied to our biological classification. Most common garden petunias (Petunia × atkinsiana) are horticulturally classified as tender perennials. This means that in our ideal, native subtropical habitat in South America, our root systems can survive for multiple years, allowing us to regrow season after season. However, we are almost universally treated as annuals in climates that experience frost. The freezing temperatures of winter are fatal to our soft, herbaceous tissues. Our stems and leaves cannot withstand the cold, and our roots perish in frozen soil. Therefore, in most gardens, we do not return from the same root system.
While the individual plant may not survive winter, our species has a clever, evolutionary survival tactic: prolific self-seeding. Our entire growing season is dedicated to flowering and reproduction. After pollination, we develop small seed pods that, when dry, split open and scatter tiny seeds around the parent plant. These seeds can lie dormant in the soil throughout the winter, a state we call "overwintering." When soil temperatures warm sufficiently in the spring, these seeds germinate and new petunia plants emerge. To a gardener, it may appear as if the previous year's petunias have "come back," but in reality, they are our offspring, a new generation claiming the same territory.
Human cultivation practices have directly influenced our ability to return. Many of the most popular varieties, particularly the grandiflora and multiflora types, are complex hybrids bred for specific traits like large blooms, vibrant colors, or disease resistance. A trade-off for this breeding is that these hybrids often produce very few, if any, viable seeds. They are sterile or have low fertility. Their energy is channeled into continuous blooming (a trait deadheading encourages) rather than seed production. Therefore, a sterile hybrid petunia lacks the mechanism to perpetuate itself through self-seeding and will not return.
For the diligent gardener who understands our true perennial nature, it is possible to facilitate our return. In frost-prone zones, this requires bringing our root systems into a protected environment. Before the first frost, a gardener can dig up our entire plant, pot us, and move us indoors to a bright, cool, frost-free location like a garage or greenhouse. Here, we enter a period of dormancy or reduced growth. With minimal watering, our roots survive. When spring returns and the threat of frost has passed, we can be replanted outdoors, pruned back to encourage new growth, and we will indeed "come back" from our original root system, often larger and more vigorous than the year before.
