From a botanical perspective, the African Daisy (Osteospermum spp. and Dimorphotheca spp.) is a sun-worshipping perennial, often grown as an annual in colder climates. Its fundamental growth requirements are non-negotiable: it demands full sun (at least 6-8 hours of direct light daily) and exceptionally well-draining soil. The plant is highly susceptible to rot in cold, wet conditions. Therefore, the primary rule for planting outdoors is to wait until all danger of frost has passed and the soil has had a chance to warm significantly. Sowing seeds into cold, soggy earth will almost certainly result in failure.
The vast climatic differences across the US mean there is no single planting date. The best guide is your local average last frost date. African Daisy seeds should be sown outdoors only after this date, when soil temperatures consistently reach 60-70°F (15-21°C).
In these warm regions, African Daisies can be perennial. The optimal outdoor sowing window is in the fall. This allows the seeds to germinate in the warm soil and establish a strong root system through the mild winter, leading to an exceptionally early and robust bloom period in the spring. For those who miss the fall window, a very early spring planting (February-March) is also successful, as the soil warms quickly. The intense summer heat can cause plants to go dormant; providing afternoon shade can help them survive to bloom again in the fall.
These regions experience colder winters and a shorter growing season. Here, African Daisies are strictly annuals. Planting must occur well after the last frost, typically from mid-May to early June. The soil must be warm and workable. Gardeners in these zones can get a head start by starting seeds indoors 6-8 weeks before the last expected frost and then transplanting the hardened-off seedlings outdoors at the appropriate time. This method ensures a longer flowering period before the first fall frost ends the cycle.
The Mediterranean-like climate of much of the West Coast is ideal for African Daisies. Planting times are very flexible. In coastal California (Zones 9-10), seeds can be sown almost year-round, with fall and early spring being prime times. In the cooler Pacific Northwest (Zones 7-8), follow the same protocol as the Northeast and Midwest, waiting until after the last frost in late April or May to sow seeds directly outdoors. The key is to avoid planting during the peak of the winter rainy season when soil is cold and saturated.
This zone can be tricky. It encompasses parts of the Mid-Atlantic, Upper South, and Pacific Northwest. The safe approach is to treat African Daisies as tender annuals. Monitor soil temperature rather than just the calendar. Wait until the soil is no longer cold and damp to the touch, which is usually 1-2 weeks after the last frost date. A late April to mid-May outdoor sowing is generally safe. In a protected microclimate, a fall planting might succeed, but it carries a higher risk of loss during a harsh winter.
