As an Osteospermum, I am a tender perennial, often treated as an annual in colder regions. My survival through winter is entirely dependent on the climate zone and the care I receive. Here is my perspective on what I need to successfully overwinter across the United States.
Fundamentally, I require protection from sustained freezing temperatures and wet, cold soil. My roots are my lifeline; if they freeze solid, I will perish. I am a sun-loving plant from South Africa, and while I can handle a light frost, a hard freeze is my greatest enemy. My ideal winter conditions are cool but above freezing (approximately 40-50°F / 4-10°C), with very dry soil and bright, indirect light.
In these warmest zones, where hard freezes are rare or brief, you can often leave me in the ground. I may become semi-dormant, ceasing most of my flowering. Please do not fertilize me during this time. The key is to ensure my soil is exceptionally well-draining. Soggy, cold roots will lead to rot. A layer of dry mulch, like straw or bark, around my base can help protect my crown from any unexpected temperature dips. Simply cut my stems back by about two-thirds after the last blooms fade to encourage a tidy, bushier form for spring.
This is a tricky zone for me. I might survive a mild winter in the ground, but it is a gamble. To increase my odds, a heavy layer of mulch (up to 6 inches) over my crown after the first hard frost is crucial. This acts as a insulating blanket. Alternatively, you can treat me as a container plant. Move my pot to a sheltered location, such as against a south-facing wall of your home or into an unheated garage or shed. The goal is to protect me from the coldest winds and precipitation. Water me only very sparingly, just enough to prevent my roots from desiccating completely.
In these climates, you must bring me indoors. I will not survive the freezing temperatures outside. The best method is to pot me up and treat me as a houseplant. Before the first frost, please prune my foliage back by about half to reduce transplant shock and minimize the space I require indoors. Place me in a bright, cool room, such as a sunny sunporch or a south-facing window. A heated greenhouse is ideal. Water me very infrequently, just enough to keep me from wilting. I will likely enter a period of dormancy, and that is perfectly normal. Do not expect flowers during this time.
When brought indoors, I can be susceptible to pests like aphids and spider mites. Please check my leaves regularly before bringing me inside and treat any infestations. The most common cause of my demise indoors is overwatering. My metabolism slows dramatically in cool, low-light conditions. Soggy soil will cause my roots to rot quickly. It is always better for me to be slightly too dry than too wet during my winter rest.
