Growing Plants Indoors Time. It takes time to grow and care for plants. Some plants require more time to grow than others. Getting crops to flower or fruit at a certain time can be challenging. Plants that normally grow outdoors need a certain number of days to flower or fruit. You can time plants to flower or fruit on a certain date. This is a good lesson in both plant science and math. Remember plants need room to grow, temperature, light, water, air, nutrients, and time. Now click here to test your new knowledge about plant parts!