Every gardener growing tomatoes waits for that first juicy, fresh, off-the-vine bite. When the wait seems to go on forever and fruits stay green for weeks, it could be that they aren't getting enough sun. Tomato plants need full sun, or closer to eight hours consistently every day, through all growth stages. When your tomatoes refuse to turn red, they could be getting too little sun. Here's what to know about how much sun tomatoes need, and our best advice on how to get them the light they need to give you the growth you want. Light Requirements for Tomatoes Though tomatoes will have different requirements for light depending on the growth stage, they need 6–8 hours of direct sunlight a day to produce the juiciest fruit—this is considered "full sun." Finding the perfect place to plant tomatoes takes some planning, as light exposure plays a major role through all stages of plant growth. In the early stages, poor light with high temperatures can decrease flower and fruit production, increase vulnerability to fungal and leaf spot diseases, and lead to pests. Later, not enough light produces straggly weak vines and small, poor-quality fruits. During fruit development, too much sun leads to a poor harvest with fruits vulnerable to sunscald, cracking, and uneven ripening. Vegetative Stage During the first 30 to 45 days after transplant, tomato plants grow vines and leaves. This is called the vegetative stage and may be a little shorter or longer depending on variety. Vines grow rapidly and use a lot of nutrients. Since nutrients are delivered through photosynthesis which is dependent on energy from light, a minimum six hours of bright, direct sun is needed during early growth. Flower/Early Fruit Stage Between 30 and 45 days you should begin to see small yellow flowers open on your plants. In this stage light energy supports flowering and fruit set. Small fruits start to form between 70 and 100 days depending on variety. Six hours of light is adequate and eight hours can boost fruit production. Excess heat begins to enter the equation and temperatures above 85 to 90 degrees can reduce flower production and fruit development. Ripening Stage Temperature becomes more important during the ripening phase about 30 days after fruit appears. Lycopene and carotene are pigments that give tomatoes their red color. Ideal temperatures for pigment to develop is 70 to 75 degrees F. When temperatures exceed 85 to 90 degrees F., pigment production is reduced and may even stop. Grown and cared for correctly, foliage shades fruits which takes heat out of direct sunlight for more uniform ripening. Six to eight hours is still needed to maintain healthy plants, especially with indeterminate varieties that produce fruit all season long. Why Morning and Afternoon Light Is Crucial Morning and afternoon light are both important for tomato growth. In the morning, the sun is high overhead, shining directly on the garden. At noon it reaches its highest point during daylight hours. This is when it is strongest, producing the greatest amount of energy.1 Morning light is important because it dries dew, decreases nutrient loss through evaporation, and initiates photosynthesis. Afternoon sun exposure extends the daily energy and growth cycle, giving tomatoes the sunlight quantity they need. The Best Tips to Make Sure Tomatoes Get Enough Sun Plant tomato varieties that grow well in your specific growing zone and climate. Mulch to lower soil temperature and improve moisture retention. Orient your plants in an east to west direction to access the first sunlight in the morning and throughout the day. Consider geographic features that reduce light availability or create microclimates. Avoid pruning or removing leaves during fruit formation and ripening. Plant corn or pole beans on the western side for protection from the hot afternoon sun. Leave adequate space between plants for good air circulation. Consider using white shade cloth which reduces heat but doesn't affect light quality.2 Harvest fruit early as soon as it shows color and keep in a shaded area to finish ripening.
















