Do Tomato Plants Need Direct Sunlight? (3 Cautions)


All plants need light to grow, including tomatoes.  If your garden is shaded, you might be wondering if tomato plants will grow there with only indirect sunlight.

So, do tomato plants need direct sunlight?  Tomato plants will always grow best with plenty of direct sunlight – 6 to 8 hours per day is ideal.  Tomato plants may still bear fruit with less sunlight, but they will not be as productive.  If growing indoors, tomato plants can grow 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.

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 shed some more light on this topic.

Do Tomato Plants Need Direct Sunlight?

According to the University of New Hampshire Extension, tomato plants grow best when they get full sun for most of the day.

ripe tomatoes on vine
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 sunlightMichigan 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 may 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

It is important to remember that a plant can get sunlight in the morning, midday, or afternoon:

  • Morning sunlight is less intense than sunlight that comes later in the day.  However, 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.
sunlight through forest
Morning sunlight is less intense than light later in the day.

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 and support more fruit.

Is 4 Hours of Sun Enough for Tomatoes?

Some tomato plants will not be able to produce much fruit with only 4 hours of sun.  As mentioned earlier, tomatoes need a minimum of 6 hours of direct sunlight per day in order to thrive and produce their best.

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 and afternoon sun exposure.  Even then, the fruit may not grow as large as it 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!

Is 6 Hours of Sun Enough for Tomatoes?

The minimum recommended 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”?

tomatoes
You want lots of tomatoes, right? So, make sure your plants get plenty of direct sunlight!

Exactly – and 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!

Can Tomatoes Grow In Shade or Indirect Sunlight?

As mentioned earlier, tomato plants will be less productive if they grow without optimal sunlight.  They are not shade-tolerant, and they prefer full sun (6 to 8 hours or more of direct sunlight per day).

Tomatoes might still grow in 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!

frosted leaf
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
  • Trim back some of the branches on nearby trees
  • Plant on the south side of your house, 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.

Can Tomato Plants Get Too Much Sun?

In some cases, tomato plants can get too much sun, giving them too much of a good thing.  This can happen to both young seedlings and established tomato plants.

Tomato Seedlings

Before you transplant tomato seedlings into your garden, they will need time to get used to the outdoor conditions.  The sudden shock of a change in sunlight, temperature, wind, and other factors makes it difficult for them to adjust.

tomato seedling
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 them 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.

sunscald on tomato
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
  • 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 lots of intense sunlight.

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.

row cover
A row cover is a white fabric that allows some sunlight through, in order to reduce intensity.

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 protection 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.

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.

I hope you found this article helpful.  If so, please share it with someone who can use the information.

If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here.  Enjoy!

~Jonathon

jonathon.david.madore

Hi, I'm Jon. Let's solve your gardening problems, spend more time growing, and get the best harvest every year!

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