From our perspective as basil plants, winter indoors is a profound shock to our system. We are tropical natives, descendants of plants from warm regions of Asia and Africa. Our entire biological clock is set by long, sunny, and warm days. When temperatures outside begin to drop, our growth slows dramatically. Moving us indoors is essential for our survival, but the environment must mimic our ideal conditions as closely as possible. We require consistent temperatures above 50°F (10°C), with an ideal range between 65-75°F (18-24°C). Drafts from windows, doors, or heating vents are our enemies, causing stress and leaf drop. More critically, we are sun-worshippers. The weak, short-lasting winter sun is often insufficient. We need the brightest spot you can provide, preferably a south-facing window where we can bask for at least 6 hours of direct light. Without adequate light, we become "leggy," stretching our stems weakly and sparsely in a desperate search for photons, which depletes our energy reserves.
You must understand that our life processes slow down considerably in winter. We are not actively growing like we do in the summer. This change in our metabolism means our thirst diminishes significantly. The greatest threat to our survival indoors, after cold and darkness, is overwatering. When our roots sit in constantly wet, cool soil, they cannot breathe. They begin to rot, a condition that quickly spreads upward, turning our stems black and mushy. Before you water, check our soil. Stick your finger about an inch deep. If it feels dry, then a thorough watering is welcome. If it's still moist, please wait. Also, avoid wetting our leaves when you water. In the stagnant indoor air, moisture on our foliage can invite fungal diseases like powdery mildew, which appears as a white, dusty coating, further weakening us.
As annual plants, our primary biological goal is to flower, set seed, and complete our life cycle. Stress, such as a significant environmental change, can trigger this reproductive instinct prematurely. You may notice small flower buds forming at the tips of our stems. While they might be pretty, from our survival perspective, this is a massive diversion of energy. Flowering and seed production consumes the sugars we would otherwise use for maintaining our leafy growth. For us to remain a viable culinary plant for you, these flower buds must be pinched off as soon as they appear. Pinch the bud back to the next set of leaves. This action signals to us to redirect energy back into leaf production and overall maintenance, helping us conserve strength for the winter months.
The move from outdoors to indoors is a jarring experience. A sudden transition can cause us to go into shock, resulting in significant leaf loss. To help us adjust, a gradual acclimation process is best. If possible, bring us inside for a few hours each day, gradually increasing the time over a week or two before the first frost. This allows us to slowly adapt to the lower light levels and different humidity of your home. Before bringing us in for the season, give us a thorough inspection. Check the undersides of our leaves and along our stems for pests like aphids, spider mites, or whiteflies. A gentle spray of water or an application of insecticidal soap can prevent these pests from coming indoors with us, where they can multiply rapidly in the protected environment and cause us great distress.
