From my perspective as an Osteospermum, overwintering is not about continued growth but about survival through a period of enforced dormancy. My genetic code is programmed for the mild winters of my native South Africa. Prolonged exposure to temperatures below freezing (0°C or 32°F) is fatal. My cells contain water that expands when it freezes, rupturing my cell walls and causing irreversible damage. My primary need is to be moved to a environment that stays consistently above this freezing point, ideally between 5-10°C (40-50°F). This cool temperature is the key signal for me to slow my metabolic processes to a near-standstill, conserving my energy for the spring.
As autumn arrives and daylight wanes, I sense the changing season. To help me prepare for my big sleep, please stop applying fertilizer. This extra nutrients would encourage tender new growth that is highly susceptible to the cold and disease. You should also gradually reduce watering. My thirst diminishes significantly as my growth slows. However, do not let my root ball become dust-dry; a state of slight, occasional moisture is crucial to prevent my roots from desiccating and dying completely during dormancy.
Where you place me is critical. A typical warm, dry living room is unsuitable. The excessive heat and low humidity will confuse my systems, potentially forcing me to break dormancy with weak, etiolated growth that depletes my reserves. Instead, I require a cool, bright space. An unheated garage with a window, a frost-free greenhouse, or a cool basement under grow lights are perfect. The light is important to maintain minimal photosynthetic function and keep my foliage somewhat healthy, even if I drop some leaves. Good air circulation in this space helps prevent fungal issues, but keep me away from harsh, drying drafts.
During this period, please understand that I will not look my best. I will likely enter a semi-evergreen or even fully deciduous state. It is normal for me to drop a significant number of my leaves, and my remaining foliage may appear slightly wilted or lackluster. This is not a sign of failure but a natural part of my energy-conservation strategy. Do not be tempted to overwater me in response. My water needs are minimal—only enough to ensure my stems and crown do not shrivel. My appearance is dormant, but life is still present within my crown and root system, waiting for the signal to regrow.
As the days lengthen and the outdoor temperatures begin to consistently rise above 10°C (50°F) in spring, I will naturally begin to show signs of life. You will notice new green shoots emerging from my base. This is the time to gently increase watering and, once I have a set of new leaves, apply a half-strength balanced fertilizer to support this new growth. After a week of acclimatization to outdoor conditions, I can be planted back into the garden, ready to thrive and flower again, grateful for your care during the cold months.
