How Much Sun Do Tomato Plants Need? A Light Requirements Guide For Healthy Growth

Tomatoes and sunshine go hand in hand. Without enough light, a tomato plant can't produce fruit. But, exactly how much sun do tomatoes need? Do they require a full sun position? And, crucially, does your garden get enough sun to grow good tomatoes? These are important questions to answer.

If you're learning how to grow tomatoes, then meeting their light requirements is key. Tomatoes ideally need 6 to 8 hours of direct sunlight each day. More is better, though you may have to take steps to protect plants in periods of high heat.

Keep reading to ensure your tomatoes get the light they need at the right time.

How Much Sun Do Tomatoes Need?

The simple answer to questions on light requirements for tomatoes is that you need a minimum of six hours to produce fruit, but eight or more hours of sun will produce the best results in terms of how many tomatoes you get.

The reason that light for tomatoes is so important is that the plants convert sunlight into energy. Tomato plants need energy to make their fruit. Therefore, the more sunshine they get, the more energy they have and the more fruit they can produce.

What Happens If Tomatoes Don’t Get Enough Sun?

While a tomato plant may survive with less than 6 hours of sun per day, it will probably produce fewer fruit. If you only get 4 to 6 hours of full sun, your best option is to plant smaller fruiting varieties like cherry tomatoes.

However, limited productivity isn’t the only issue with a lack of sun. Tomato plants lacking sunlight are often stunted or leggy, they may have chlorotic foliage and few leaves. When the plants have very little light, they generally have a failure to thrive and may even die.

Can Tomatoes Get Too Much Sun?

While tomatoes are indeed sun lovers, too much of a good thing can be problematic. Just like when you get too much sun, you become sunburnt, tomatoes do too – especially if the plants are exposed to the sun midday, when temperatures are at their zenith.

A combination of high temperatures and full sun can result in sunscald. It causes white, blistered areas of fruit, which over time become grayish white patches with a husk-like texture.

Sunscald is most common in plants that are less than robust. Those that have been pruned too much, have a disease, or succumb to insect feeding.

Best Locations for Tomato Plants

To maximize the amount of sunlight your tomatoes receive, position the plants in the garden where they will get both morning and afternoon sun. Consider a south-facing wall or a sheltered area on the south or south-west of your garden.

If planting tomatoes in an area that gets more than 8 hours of sun, especially in regions of high heat, you may need to take steps to protect the tomato plants from sun damage. Mulching tomato plants, setting up a shade barrier, watering on a consistent basis, and even growing tomatoes in containers that can be moved out of the midday sun are all ways to protect your plants from overly hot temperatures and direct sunlight.

To take total control of how much sunlight your plants get, you can grow tomatoes in a greenhouse or use supplemental lighting indoors. Growing tomatoes indoors requires full-spectrum LED grow lights set on a timer for 14 to 16 hours per day for mature plants and 18 to 22 hours for young seedlings. Make sure the grow lights are positioned about 6 to 12 inches (15 to 30cm) from the plants. As the plants grow, gradually raise the light fixture.

Do Tomato Seeds Need Light to Germinate?

Despite the fact that tomato seedlings and mature plants need plenty of sunlight, interestingly, tomato seeds do not need light to germinate. They do, however, need consistent moisture and warmth.

How Much Light Do Tomato Seedlings Need​?

Once the seeds have germinated and you see the first set of true leaves, the tomato seedlings will need significant light – about 18 to 22 hours of supplemental light in the form of LED grow lights or 14 to 16 hours of bright outdoor light.

Light Requirements for Tomatoes to Ripen

While tomato plants require significant sunlight to grow and produce fruit, once the fruit is on the vine, it doesn't need light to ripen. In fact, light can actually hamper ripening.

The tomato ripening process is facilitated by heat and the production of ethylene gas, the ripening agent emitted by tomatoes that is responsible for color change, softening, and flavor development.

How to Maximize Sunlight

There are several things you can do to maximize sunlight for your tomato plants:

• Grow tomatoes in containers that can be moved into sunnier areas of the garden throughout the day. The EZ Self-Watering Tomato Planter, available in the Gardening Know How Shop, features wheels for easy mobility, plus a trellis to support plants.
• Prune back nearby plants or even the tomato foliage itself to promote better sunlight penetration. Just remember to be judicious when pruning tomato plants and never take back more than a third of the plant.
• Another option to maximize sunlight is to use mirrors or other reflective items (old CDs, for instance) to bounce light back onto the plants.
• Lastly, if you just don’t have enough sunlight, consider growing types of tomatoes that are tolerant of partial sun, or varieties that produce small fruit, such as Black Cherry, Evans Purple Pear, Golden Sweet, and Juliet Hybrid. Partial sun or shade tomato varieties include heirloom tomatoes like Cherokee Purple and Black Krim.

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