Tomatoes are among the most popular fruits in gardens around the world, and tomatoes are a fixture in all sorts of dishes and cuisine.
But, these climbing plants have high nutritional requirements and particularly can be fussy or prone to failure when they don’t get enough sun. So, how much sun do tomatoes need?
6 to 8 hours is generally enough for tomatoes to grow, with as much as 9 hours of the sun being required depending on the stage of growth.
Tomatoes require copious, direct sunlight at all stages of growth, but growers are cautioned to protect them from intense heat as they may be damaged or even killed by it.
That’s a good rule of thumb that you can generally live by no matter what type of tomatoes you are growing, but, as you likely already know, the devil is in the details if you want to grow healthy tomatoes and harvest them.
Keep reading to learn everything you need to know about how much sun tomato plants require.
Can You Grow Tomatoes in the Shade or Partial Shade?
Tomato plants are sun-hungry. They require lots of nutrition from photosynthesis at all stages of their life cycle, growth, flowering, fruiting, and ripening, and that means they need lots and lots of sun.
Accordingly, if they are kept in the shade or are partially shaded completely for half the day, they will not be able to get the nutrition from UV that they require.
At best, your plants will falter or produce lackluster tomatoes, but at worst they might fail to fruit entirely or even die back.
That being said, during the hottest parts of the day with the most intense sunlight they might need a light covering of shade cloth to prevent them from overheating, which can also injure or kill them.
My own tomatoes were grown within a sort of pergola with a retractable, coarse shade cloth that I could unfurl or stow at will in seconds.
This would allow my tomatoes to still get some UV value during the hottest parts of the day, but was still sufficient to shield them from the worst of the heat. Prior to that trick, I had lots of trouble with heat stress on my plants!
If you do want to grow tomatoes in the shade, you do have some options, though.
Certain species of small or cherry tomatoes can grow reasonably well in the shade since they require less sun overall to fruit successfully.
Additionally, you can use reflective surfaces placed strategically nearby in the form of light-colored walls or panels or even arrays of mirrors to bounce sunlight onto your tomato plants to good effect.
Do Tomato Plants Prefer Morning or Afternoon Sun?
Tomato plants don’t really prefer a specific time of sun over the other- UV is UV when it comes to photosynthesis!
But what matters is knowing how the timing of the sun will affect the plant in other ways and thus affect your plans. Morning sunlight is less intense but still provides essentially full value nutrition to the plant.
This makes it ideal for starting plants off on the right foot by nourishing them after a period of darkness and also warming them up gently for more intense sunlight ahead. Late afternoon and evening sunlight is much the same for this purpose.
Midday sun is a time of tremendous energy generation for tomatoes, but it is also going to significantly heat up the plant and the fruits in particular.
This is when you might need to shade your tomato plants in order to protect them from this outcome.
Do Tomato Plants Need Varying Amounts of Sun at Different Stages of Growth?
Yes, although their requirements don’t vary too much. In general, as the plant grows and develops prior to the fruiting stage, you can get away with slightly less sunlight, perhaps as little as five hours (occasionally) but between 6 and 8 hours will be ideal.
However, flowering and later fruiting will impose tremendous demands when it comes to nutrition, and this is when tomato plants will need maximum sunlight, at least 8 hours and maybe even 9 for a plant that is tall and mature.
But as mentioned, you must be careful since intense, direct sunlight can easily damage flowers and fruits alike if it is allowed to overheat them.
The flowers in particular are pretty notorious for dropping during high heat conditions, but know that they will reflower if they aren’t overly stressed from prolonged periods of high heat.
As another rule of thumb, tomato plants can get away with a little bit less sun early in their life cycle, but will need more sun later in their life cycle.
What Happens if Tomatoes Don’t Get Enough Sun?
Inadequate sunlight is devastating for tomato plants, with the lack of nutrition being detrimental for their development and maturation. Flowering will be limited and the development of fruits stunted if it occurs at all.
It is imperative that you plan on getting your tomato plants maximum sunlight at all phases of development, and growers are advised to plant them in a north-south arrangement so that may take maximum advantage of morning and evening sun without unduly shading their neighbors.
However, tall tomato plants can be difficult to shade, especially if you are relying on other plants nearby for the job.
Strategic planting with a pergola (like I used above) or using even taller plants like sunflowers in a westerly orientation is a good idea if you want to afford your tomatoes a little bit of shade when they need it most.
Beware of Sunscald
Getting tomatoes enough sun without damaging them can be a challenging balancing act for even seasoned gardeners. Sunscald in particular has been the bane of many tomato harvests pretty much forever.
Sunscald is a condition where tomato fruits receive too much direct sun, or rather, are overheated by intense direct sunlight. The fruits will respond by discoloring and hardening, essentially ruining them for your purposes.
It is easily noticed, but once it is it is usually too late to save the affected fruit. You can prevent it by following the tips presented in this guide and taking great care to prune and harvest strategically
This way, the ripe fruits are removed before they can be scalded while developing fruits are afforded a little bit of shade during the hottest parts of the day.
Tom has built and remodeled homes, generated his own electricity, grown his own food and more, all in quest of remaining as independent of society as possible. Now he shares his experiences and hard-earned lessons with readers around the country.