From our perspective as Osteospermum plants, our water needs in a hot summer climate are a direct response to two primary forces: the intense evaporative demand of the atmosphere and our own biological imperative to keep our root zone consistently moist but never saturated. The hot sun and dry winds pull moisture from our leaves (transpiration) and the soil surface (evaporation) at a dramatically accelerated rate. To compensate, we require more frequent water intake to maintain turgor pressure—the internal water pressure that keeps our stems upright and our leaves unfurled. Without adequate water, our cells lose this pressure, leading to the wilting you observe, a clear distress signal.
Our water needs are highest immediately after being planted. During this establishment phase, our root systems are limited and confined to the original root ball. We cannot yet seek out moisture from the surrounding soil. Therefore, we require deep, thorough watering every day, or possibly even twice a day during extreme heat waves, for the first one to two weeks. This consistent moisture encourages our roots to grow vigorously outward and downward into the native soil, which is the key to our long-term survival and drought tolerance. Please do not let our root ball dry out completely during this critical period.
Once we are established, our watering schedule shifts. Our preference is for a deep, infrequent soaking rather than frequent, light sprinklings. A light sprinkle only dampens the top layer of soil, encouraging our roots to stay shallow where they are vulnerable to heat and rapid drying. A deep watering, which moistens the soil to a depth of 6-8 inches, encourages a deep, extensive, and resilient root system. The ideal practice is to water us slowly and deeply at the base, allowing the water to penetrate fully. Then, allow the top 1-2 inches of soil to dry out before watering us again. This cycle of soak-and-dry provides us with ample moisture while allowing crucial oxygen to reach our roots.
You can significantly aid our water retention efforts by applying a 2-3 inch layer of organic mulch, such as wood chips or bark, around our base. This mulch acts as an insulating blanket, protecting our shallow roots from extreme heat and drastically reducing the rate of evaporation from the soil surface. Furthermore, the soil we are planted in is fundamental. We thrive in well-draining soil. Heavy, clay-like soils that remain waterlogged will suffocate our roots and lead to root rot, which is just as detrimental as drought. Amending the soil with compost at planting time improves both its water-holding capacity and its drainage, creating the ideal environment for our root systems.
Please learn to read our signals. A slight wilting of our leaves during the hottest part of the afternoon is a normal physiological response to reduce leaf surface area and conserve water; we will often perk up again in the evening as temperatures drop. However, if we are still wilted in the morning, that is a definitive cry for help and requires immediate deep watering. Additionally, observe our flowering. A significant reduction in blooming or the production of smaller flowers is another indicator of water stress. When our survival is threatened, we divert energy away from reproduction (flowering) and towards simply staying alive.
