tomato light requirements

All plants need light to grow, including tomatoes - but the question is, how much? If some parts of your garden are shaded, you might be wondering if tomato plants will grow there or not. So, do tomato plants need direct sunlight? Tomato plants grow best in direct sunlight – 6 to 8 hours daily is ideal for optimal fruit production. Tomato plants can still bear fruit with less sunlight, but they will not be as productive. Tomato plants can grow indoors without direct sunlight if you provide the right type of artificial light. Of course, it is possible to have too much of a good thing. Too much sunlight during a dry spell will leave your tomato plants thirsty and will slow down fruit production. In some cases, too much sunlight will damage the fruit after it appears. It can also affect the acidity of the tomatoes themselves. In this article, we’ll talk about how much direct sunlight tomato plants need and ways to provide more. We’ll also talk about what happens when tomato plants get too much sunlight and how to prevent this problem. Let’s gets started. Do Tomato Plants Need Direct Sunlight? Tomato plants need direct sunlight to maximize fruit production. According to the University of New Hampshire Extension, tomato plants grow best when they get full sun for most of the day. Tomatoes are warm-weather crops, and they prefer warm temperatures and bright light (they are originally from tropical areas in South America). Tomato plants will grow best with full sun: 6 to 8 hours or more of direct sunlight per day. There is some debate about what “full sun” means, but in general, full sun means at least 6 hours per day of direct sunlight. Michigan State University suggests: “To do well, tomatoes need eight or more hours of full, uninterrupted sun.” https://www.canr.msu.edu/news/growing_tomatoes_in_your_garden Although tomato plants can still bear fruit with less sunlight, you may not get as many tomatoes as you were hoping for. The Ohio State University suggests that: “Tomatoes will not be as productive if they receive less than optimum sunlight exposure." https://ohioline.osu.edu/factsheet/HYG-1624 In my experience, tomato plants growing in shaded parts of the garden start producing fruit later in the season, and they produce less fruit overall. Tomato plants that grow indoors on a shady windowsill might not produce as much fruit as plants in full sun. If you want to harvest more fruit, it is important for your tomato plants to get enough sunlight during the day. Remember that a plant can get sunlight in the morning, midday, or afternoon, and the intensity varies: Morning sunlight is less intense than sunlight that comes later in the day. Morning sunlight gives plants energy without subjecting them to the extreme midday and afternoon heat. Midday sunlight occurs when the sun is overhead, at its brightest and hottest. You will have to consider the tradeoff between bright sunlight and excessive heat. In extreme cases, you might need to protect your plants from midday sun (more on this later). Afternoon sunlight occurs when the sun has started to set from its overhead position. It is more intense than morning sunlight, but not as strong as midday sunlight. The table below summarizes the three basic types of sunlight: Type Of SunlightIntensityMorningLeast IntenseMiddayMost IntenseAfternoonModerateThis table summarizes the 3basic types of sunlight and their intensity. As long as your tomato plants get 3 to 4 hours of direct sunlight in both the morning and afternoon, they should be able to produce plenty of fruit. Stronger sunlight and a longer duration of sunlight will both help the plants to grow larger and faster, which means they can support more fruit. Morning sunlight is less intense than light later in the day. Is 4 Hours Of Sun Enough For Tomatoes? Four hours of sun is probably not enough for most tomatoes, at least if you want to get a good harvest. Tomato plants that only get 4 hours of sunlight may still produce some fruit, but not as much as if they got 6 to 8 hours or more. If you can only manage 4 hours of sunlight for your plants (on a balcony or windowsill), try to make sure that the light comes from midday or afternoon sun exposure. Even then, you may not get as much fruit as you would with full sunlight. If your plants don’t get enough sunlight, you may find that they grow tall to reach for more sunlight, but never produce any fruit. Tomato plants that don't get enough sun might grow tall when trying to reach for the light. However, they might not produce any fruit! According to thegardeningcook.com, some plants are shade tolerant, but tomatoes are not high up on that list! If you are worried about a lack of sunlight for your balcony or windowsill tomato plants, consider using a grow light to supplement the sunlight. Just make sure not to leave it on all night! Is 6 Hours Of Sun Enough For Tomatoes? Six hours of sun is just enough for most tomatoes if you want to optimize fruit production. The minimum recommended daily amount of sunlight for tomatoes is 6 hours. With 6 hours of sun, most plants will be able to produce some fruit. Let’s be honest though – if you are doing all of the work that goes into a garden, do you want “some fruit” or “lots of fruit”? You want lots of tomatoes, right? So, make sure your plants get plenty of direct sunlight! Exactly – you want lots of fruit! To get the best harvest possible, you should aim for 8 hours or more of direct sunlight per day. Don’t settle for fewer tomatoes just because you didn’t choose a sunny spot! (or didn't use a grow light indoor plants) Can Tomatoes Grow In Shade Or Indirect Sunlight? Tomato plants can grow in shade or indirect sunlight. However, as mentioned earlier, they will be less productive if they grow without optimal sunlight. Tomatoes are not shade-tolerant, and they prefer full sun exposure (6 to 8 hours or more of direct sunlight per day). Tomatoes might still produce fruit with indirect sunlight, depending on how intense it is and how long they are exposed. However, they will grow better and produce more with at least some direct sunlight. Full shade is not good for tomato plants, so you should not expect much fruit until late in the season, if at all. This is a big problem in climates with a short growing season! A short growing season and a lack of sunlight may leave you with no fruit when frost ends the tomato growing season! There are at least a few reasons I can think of that you might end up with tomato plants in a shady location: The spot you planted was sunny when you chose it, but became shady when leaves grew thick on nearby trees later in the season You planted too close to the house (or another building) You are growing indoors on a windowsill that doesn’t get enough sun If you want to provide your tomato plants with more sunlight, there are a few things you can do: Choose a sunnier spot in your garden for next year Move any potted tomato plants to a sunnier location Choose a new location for raised beds Trim back some of the branches on nearby trees Plant on the south side of your house (in the Northern Hemisphere), if you want to grow close to the house Move indoor plants to a windowsill on the south side of your house Finally, if you want to grow indoors, you can use artificial light in the absence of sunlight (for example, in a basement or a room without big windows). Here is an article from yardthyme.com on growing tomato plants indoors using LEDs. (If you want some LED grow lights for indoor plants, you can find them online from Ace Hardware). Can Tomato Plants Get Too Much Sun? Tomato plants can get too much sun in some cases. Seedlings that are not ready for full sun exposure can suffer from strong sunlight. Make sure your tomato plants are hardened off and ready to go before you transplant them outdoors! Strong sunlight can also damage the fruit of established tomato plants if it is intense enough. Intense sunlight can also damage tomato plants if you prune them too heavily at the top. Tomato Seedlings Before you transplant tomato seedlings into your garden, they will need some time to get used to outdoor conditions. The sudden shock of a change in sunlight, temperature, wind, and other factors makes it harder for them to adjust. Tomato seedlings need some time to adjust to outdoor conditions. Let them get used to it gradually. To help them along with the transition, it is important to harden off your tomato seedlings. To do this, gradually give them more exposure to outdoor conditions over a period of several days. Keep them in containers (seed trays or pots) until they have been hardened off and are ready to plant in the garden. That way, you can easily move a group of plants into and out of the elements (sun, rain, wind). If you want more details, you can learn all about how to harden off seedlings in my article here. Established Tomato Plants Established tomato plants have made it past the seedling phase to grow into mature plants. However, they will still suffer if they get too much sunlight. For one thing, excessive sunlight will cause higher temperatures and faster evaporation of water from the soil. This one-two punch denies tomato plants the water they need to grow and produce fruit. Also, the leaves of tomato plants will curl in response to heat and lack of water. This reduces the surface area of the leaves so they don’t lose as much water due to transpiration and evaporation. Unfortunately, wilted leaves allow more sunlight through to the fruit. This can lead to another problem that affects the fruit: sunscald. Sunscald occurs when intense, direct sunlight causes a white or tan spot on a tomato fruit. A tomato fruit that gets exposed to too much strong sunlight will develop white or tan spots (sunscald). Sunscald is more likely if: you prune your tomato plants too aggressively (especially near the top of the plant) your plants are exposed to strong midday sun without any shade or protection your plant’s leaves wilt due to lack of water you use stakes instead of cages to support your plants Finally, remember that excessive heat (caused in part by sunlight) can prevent fruit set. According to the University of Arizona Extension: “Tomatoes set fruit only when night temperatures are above 55 degrees Fahrenheit and when daytime temperatures do not exceed 90 degrees Fahrenheit.” https://extension.arizona.edu/growing-tomatoes Even if your fruit does form, it does not need light in order to ripen. In fact, according to the University of Michigan: “Warm temperatures are more important than light in ripening the fruit.” https://extension.umn.edu/vegetables/growing-tomatoes#soil-testing%2C-fertilizer-and-mulch-173060 So, don’t be afraid to take steps to protect your tomato plants if they are getting too much intense sunlight during the day. How Do I Protect My Tomato Plants From Too Much Sun? There are a few ways you can protect your tomato plants from too much sun. The name of the game is to find a way to provide natural or artificial shade for them. One method is to set up an “umbrella” of sorts to protect your tomato plant. To do this, drape a shade cloth or row cover over a stake or cage that is supporting a tomato plant. A row cover is fabric that allows some sunlight through, in order to reduce intensity while still allowing the plants underneath it to grow. You can learn more about covering your plants in my article here. Perhaps you like to build things, or you need to provide shade for multiple plants. In that case, you can use an arbor, trellis, or pergola instead. Of course, the structure itself will provide some shade during the day for any plants growing underneath. However, you can also grow vining plants that will climb and crawl up the structure to give extra shade during the day. Another option is to drape a piece of row cover or shade cloth over one of these structures to provide shade. If you want to learn more about these structures, you can head on over to my article where I explain them in more detail. Finally, avoid over pruning your tomato plants! When you cut off suckers (vines), you also remove leaves. Without enough leaves, the fruit does not have enough shade to protect it from sunlight. This will make it more likely that your tomatoes will suffer from sunscald. Keep your plants watered to ensure that the leaves do not wilt. Non-wilted leaves will provide more shade for the fruit. Keep your tomato plants watered to prevent wilted leaves and the sunscald that can affect fruit. Conclusion Tomato plants can still produce fruit without direct sunlight, but they would need an artificial light source to grow indoors, or indirect sunlight outdoors. Remember that you will always get a better harvest if your tomato plants get full sunlight. If you are preparing for the upcoming gardening season, check out my article on what to do before planting tomatoes. To learn more, check out my article on where to plant tomatoes for optimal growth and fruit production. You might also want to read my article on why tomatoes grow slowly (and how to fix it). You can get a summary of vegetable plant care basics with this free app I made. I hope you found this article helpful. If so, please share it with someone who can use the information.