While some plants flower in the Winter, others can produce fruit in the summer. But how does the plant know when it’s the right time?Plants have naturally light-sensitive receptors called phytochromes. And these cells can detect light, as well as light duration. The duration of light and darkness a plant needs to flower can be called the critical photoperiod and it’s something that growers need to be aware of to get the most out of their crops.ContentsDo plants need darkness to grow?What is DLI in plantsDo plants need darkness to grow? Plants can be categorised into three groups: long day, short day and day neutral plants.What is long day plants and examples?Plants that are happy to stay in the sun for a long amount of time are referred to as long-day plants. In order to flower, these plants need more than 12 hours of sunlight a day. Examples might be things like lettuce, radishes and peas – things you’ll typically find in the garden in warmer weather.What are examples of short day plants?On the other side of the spectrum, you have short-day plants, which need longer periods of darkness – this is typically more than 12 hours. Short day plants include cotton, sugar cane and poinsettias.Whether it’s a long-day or short-day species, they still need a period of darkness. And it’s this regular routine of light and dark that triggers photoperiodism.What are day neutral plants with examples?There are a few anomalies of course. Day-neutral plants will flower whether or not they have a lot of darkness or a little darkness. One common day neutral plant would be tomatoes.Photoperiodism refers to how the plants respond to their exposure to light and darkness.What is DLI in plants When researching about the type of plant you’re looking to grow, you may have heard the term Daily Light Integral – or DLI. The DLI refers to light duration, or the amount of light and its intensity your plants are exposed to during a 24-hour day.To see great results in your plants, the best thing to do is to ensure your plants receive the same amount of light each day. That way, the plant can create routine and grow more consistently, the best way to do this Is with a timer or controller, which can automatically turn your lights on and off when necessary.Understanding the DLI of your plant will help you to create the perfect conditions in order for photoperiodism to occur.