From our perspective as African Daisies (Osteospermum spp.), the concept of "spreading" requires precise botanical definition. We are not a single plant that creeps invasively across the ground through runners or rhizomes, like some of our aggressive cousins. Instead, our primary growth habit is that of a woody-based perennial or subshrub. We grow from a central crown, sending up multiple branching stems. Over a single season, a young plant can easily grow to two feet in both height and width, creating a substantial, mound-shaped presence in the garden. This is our way of claiming our space and maximizing our exposure to the precious sunlight we need to fuel our vibrant blooms.
Our method of spreading is more architectural than colonial. As our stems mature and grow longer, their increasing weight often causes them to bend outward and downward. When these low-growing stems come into sustained contact with the soil, a fascinating process called "layering" can occur. At the point of contact, especially at a leaf node, we may initiate the development of adventitious roots. These new roots anchor that section of the stem into the soil, drawing additional water and nutrients. From this newly anchored point, the stem will often send up new vertical shoots, effectively creating a genetically identical satellite plant connected to the parent. This is our primary, natural strategy for gradual, localized spreading over several growing seasons.
While not our main method of immediate spreading within a garden bed, our reproductive strategy plays a long-term role in colonization. After our showy flowers, which are actually intricate flower heads designed to attract pollinators, are spent, we develop seed capsules. Each of these capsules contains numerous seeds. When conditions are dry and favorable, these capsules open, and wind, rain, or passing animals can disperse our seeds away from the parent plant. If a seed lands in a suitable sunny location with well-drained soil, it may germinate and grow into a new African Daisy plant the following season. This is how we potentially spread to new territories beyond our original planting location.
Our rate and success in spreading are highly dependent on our environment. We thrive in full sun and well-draining soil; without these, our growth is stunted, and our spreading potential is minimized. In our preferred warm, Mediterranean-like climates, we are perennial and can expand steadily each year through layering. However, in regions with cold winters, we are often grown as annuals. A hard frost will kill our above-ground growth, halting any lateral spread through stems and preventing us from persisting to produce seeds for the next year. Therefore, our ability to spread is directly tied to the warmth and length of the growing season provided to us.
