Indoor rosemary plants do best when grown on a windowsill that receives plenty of sunlight. If an appropriate area is not available, fluorescent or halide lights can be used. The plant should be pruned so it does not outgrow its pot, and it should be kept fairly dry because too much water can kill it. Terracotta pots allow excess moisture to evaporate between watering sessions.
If the rosemary plant is being grown in a hot climate, it requires a good deal of air circulation. The plant should be kept in a temperature zone between 50 and 80 degrees Fahrenheit. A ventilated soil that drains quickly is ideal for indoor rosemary. The plant should be fertilized regularly, using either controlled-release pellets or a liquid fertilizer.
One of the most frequent issues with indoor rosemary is powder mildew, which is caused by over-hydration, not enough light or a lack of air circulation. If there is white powder on the leaves, infected areas must be removed and disposed of in sealed bags immediately. Powder mildew can be treated with baking soda or neem oil. It is important to avoid chemical treatments if the rosemary is to be used as food. Treatments should be tested on individual leaves before being applied to the entire plant.