Gardening for me is all about negotiating my available sunlight. My property has, and is surrounded by lots of towering, mature trees.
As much as I love the Douglas fir that stands tall in the sunrise and the tulip poplar that is always framed beautifully against the sunset, they sure do make growing vegetables a challenge.
When I opt to grow sun-hungry plants like tomatoes, I know that I’m going to have to use one of my precious full sun areas to keep them happy.
That’s because tomatoes like a lots of sun. They simply can’t produce properly without it.
I can get away with planting my kale or peas in a little bit of shade, but not my ‘Supersweet 100’ or my ‘Mortgage Lifter’ plants.
In our guide to growing tomatoes, we cover how to cultivate these delicious nightshades. In this article, we’ll go over the sun needs of these plants.
Just how much sun are we talking about? That’s what’s coming up. Here’s what we’ll discuss:
Seeds and Seedlings
Let’s start at the beginning, when you’re starting seeds in your home for transplanting out after last frost. How much light do they need?
Tomato seeds don’t depend on light to germinate, so you don’t need to put seed trays or pots under grow lights or on a windowsill.
After the seeds germinate, the seedlings will need about six hours or more of direct light per day.
This can be achieved by placing the pots or trays in a south-facing window or in a greenhouse if you have one available.
Otherwise, you might need to provide some supplemental lighting in the form of grow lights.
You’ll also need to make sure that the grow lights are set at an appropriate distance from the developing seedlings.
This will depend entirely on the strength of the lights, the size, and whether or not you use reflectors.
The manufacturer will often have recommendations on the packaging or on their website.
If you notice your seedlings becoming leggy, that is an indication that they don’t have enough light. If they are exposed to too much light, they may start to turn white.
Mature Plants
Tomatoes want all the sun they can get. In gardening terms, we call this full sun, which is six or more hours of unfiltered, direct sunlight per day.
But for abundant growth and lots of fruits, more is even better. I’ve never met a tomato plant that would say “no” to eight or more hours of sun.
These plants originally evolved in sunny, warm areas of South America.
Even though plant breeders have refined them to increase production and select for different types of fruits, their need for lots and lots of light hasn’t changed.
I’ve grown tomatoes in partial sun, which translates to about four or five hours of direct sunlight per day.
My plant was less productive and the fruits were less impressive than they had been when I grew that same cultivar in proper light.
The more light you can give your plants, the healthier and more productive they’ll be.
I know we can’t always be picky, but if you have unlimited options in your garden, put your plants somewhere they will receive sunshine first thing in the morning.
This will evaporate the dew off the leaves, flowers, and fruits, and reduce the chances of fungal issues.
A little afternoon or evening light to evaporate any moisture from rain or irrigation is welcome, too.
If you can only provide six hours in the middle of the day, it is what it is.
But in a perfect world, your plants would be greeted by four hours of direct morning sun and then enjoy the light all afternoon until sunset.
That’s describing my perfect day, too! Maybe I’m part tomato.
Exceptions
If you live somewhere hot where temperatures regularly climb above 90°F during the summer, you can absolutely give your plants a little afternoon shade during the hottest part of the day.
This can help to prevent sunscald and stress. If you have just a few hot days, you can put up some shade cloth or an umbrella to provide some temporary relief.
Make sure you keep on top of watering during very hot weather.
Whether you decide to cover your plants or not, make absolutely sure the soil stays consistently moist but not soaking wet. This will support them during the heat.
Here Comes the Sun
When I think of summer fruits or veggies, it’s tomatoes that always come to mind.
I honestly can’t think of anything better than biting into a juicy heirloom that is still warm from the sun.
Without the right amount of sun, I’m going to be left with a mealy mouthful of underripe fruit – if I have any to harvest at all.
Are you growing tomatoes? Do you have a sunny garden or are you like me, with just a few areas of sufficient light? Let us know in the comments section below!
And for more information about growing tomatoes in your garden, add these guides to your reading list next: