How Much Sun Do Tomatoes Need?

Tomatoes love sunlight. That is an understatement. Every practicing gardener knows that tomato plants love and depend on sunlight for their daily growth and ripening. What some gardeners never find out is that a lot of sunlight is actually dangerous to them, as is so little of it.

This brings us to the question. How much sun do tomato plants need? Does the amount vary during the day or do the plants require a certain standard temperature throughout for them to grow well and mature on time? Well, the answer is quite simple. For starters, we have to look at the whole growth process of a tomato plant and all its different phases.

Why Do Tomato Plants Need Sun In The First Place?

Tomatoes are a warm weather fruit with a soft outer coating that turns red when ripe and a juicy fleshing inside that is edible. A number of varieties such as the Early Girl, Matina, Stupice, Glacier etc are available today and can be divided into the quicker growing varieties and those that take longer to mature. Earl Girl and Glacier, for example, are quick growing varieties and take about 50 -75 days from pollination to ripening.

All plants need sunlight to meet certain requirements for different phases of their growth and tomatoes are no different. These requirements are always changing, mainly because of physical changes within and around the plant. Tomatoes need sunlight to manufacture food for growth.

The plant leaves absorb sunlight and use the green chlorophyll pigment in them to manufacture food for the plant in form of starch. This food is a source of energy for the whole plant, which in addition to the other nutrients from the roots, is a big requirement for everyday growth.

Early Growth/ Transplanting Phase

early-spring-tomato

During the early stages of growth, tomato plants are usually kept inside and grown in manageable places such as pots. After a few days, they are exposed to the sun for only a limited number of hours a day. When they finally grow up to 6 to 10 inches tall, they are then deemed fit for movement and transplanted to a garden.

Newly planted tomatoes need all the sunlight they can get to develop. This is because its energy is required to support the plant’s huge growth needs such as growing roots and developing new leaves, which result from adapting to new soils.

Flowering Phase

flowering-tomato

Flowering is the stage in tomato growth where new flowers are fully formed and then pollinated by nature (wind, water) or humans. It is through pollination that pollen grains find their way onto the flower’s stigma, starting on a phase that ends with formation of a tomato at the receptacle. Tomatoes, just like any other plants, need enough sunlight during flowering to enable full development of the flowers and fruits.

At optimum temperature, normal flowering will occur. But if the plant gets exposed to too much sunlight during the day (i.e. temperatures higher than 85F), blossom drop will occur. Blossom drops happens when fully developed flowers drop off the plant instead of developing into fruit.

Another possible result of exposure to very high temperatures during this phase is the burning up of pollen. As a result, pollination will be hampered for some time until new pollen grains are formed. This explains the no-fruit formation spells during very hot days.

Ripening Phase

ripening-tomato

This shouldn’t be called a phase of its own, but it’s got some quite distinct sunlight requirements. For the record, tomatoes need warmth, not lots of heat or light, to ripen successfully. For ripening to happen, two chemical substances, lycopene and carotene have to be released within the tomato.

These substances give it the ripe red colour but can only be released at optimum temperatures. That is why the whole ripening process occurs best at temperatures ranging from 68F to 75F and stops happening when they go below 50F or above 85F. Tomatoes left to ripen at such high temperatures tend to have a yellowish orange look and a not -so-great taste.

How Much Of Sunlight Soes Tomatoes Plant Need?

There is no definite measure or quantification for the average amount of sunshine a tomato plant needs daily. So far, only its rate of exposure to the sun can only be monitored and limited to allow proper development throughout the phases.

Gardening experts everywhere agree on and recommend exposure to temperatures of between 68F to 75F for a maximum of six to eight hours a day during the whole growth process. For the plant’s sunlight requirements over a single day, they also suggest certain additions and tips that can be borrowed such as:

  • Morning Sun

During morning hours, the tomato plant should be exposed to a good amount of sunshine as long as the temperature range is okay. This is especially necessary to dry off dew and excess water which can be dangerous if left on the leaves for a long time. Morning light is usually intense but still beats down mildly without typical harshness of mid-day sunlight.

  • Noonday Sun

Depending on your location, you need to provide shade to the tomato plants. During this time of the day, the sun beats down hard so it is an appropriate step to reduce the strain on the plants by providing shade to them.

  • Afternoon Sun

Just like the suitability of morning sunlight, afternoon sunlight is also a boon for the tomato plants. The heat is mild during this time of the day (after 2pm) and combined with the morning sunlight, it provides suitable growth to the tomato plant.

  • During the night

Tomato plants actually need a certain amount of warmth at night. Experts recommend building a wall next to the tomato garden whose main purpose is to absorb sun rays during day and radiate them back to the plants at night in form of heat. This method is ideal for places with cold nights.

What Are The Effects Of Excessive Sun Exposure On Tomato Plant?

You might be wondering what the whole fuss about sunlight requirement is all about. By virtue of its intensity, over exposing tomato plants to the sun comes with a whole lot of disadvantages to the both the fruit and the plant itself. These are some of the effects.

Sunscald:

You can always know it is sunscald when you notice light coloured leathery patches in different places across the most exposed surface of the tomato. Tomatoes affected by this condition are prone to getting spoilt quickly; they are likely to get rotten fast!

Wilting:

This condition occurs when the plant loses a great deal of water through transpiration after exposure to higher temperatures for a long time. Wilting is best shown by dried up plants with droopy leaves and stems, colour change in leaves, uneven ripening of the tomato and gradual rotting.

Blossom drop:

This is by far the most discouraging. Due to mainly too much sunlight, fully developed flowers on the tomato plant may fall before turning into fruit. Each flower is a possible tomato. Having them all fall off one by one is a sign that something is wrong. While there are many other possible causes of blossom drop, high temperature are still marked out as the biggest of them all.

Leslie J. Shearer
 

Gardening is my passion and I have a deep relationship with nature. Growing plants and digging deep to germinate flowers and vegetables brings positivity in my life. With this blog, I hope I will be able to share my wonderful gardening experiences with the interested readers.

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