How Much Sun Does A Tomato Need To Grow? Can You Plant In Shade?

Tomatoes are extremely popular vegetable to grow from seeds at home and for many people it is the first vegetable they ever grow in their garden. So if you are a beginner you may be wondering how much sun does a tomato actually need to grow? Will it only grow in full sun.

Tomato plants, like all flowering plants definitely prefer to be in a full sun location and the generally the advice that is given is between 6 and 8 hours sun per day. However, a 1994 academic study sought to quantify how much shading really affected yield of tomato plants. In this study they found that a reduction of 30% of the sunlight would result in a reduction in the yield of a round 25%.

However, it should be noted that the limitation of this study was it that it was conducted using shade cloth. This means that the sunlight applied to the plant occurred throughout the day rather than at certain times of the day which is what is far more likely to happen in someone’s garden.

Despite this, it does give a good indication that you probably need at least 4 to 5 hours of sun to get a reasonable yield, particularly if you live in places like the UK where the peak temperatures achieved in summer are relatively low. This will result yields being lower than what you would get in warmer climates.

What is the best time of the day for a tomato plant to be exposed to direct sun?

If your site allows for you to choose whether you get morning, midday, or afternoon sun on your plants you maybe wondering which time is the best. Generally, the hottest part of the day is when the sun is at its highest point, which is from midday to around 4pm. So that would be the ideal time for the plant exposed to sunlight to give you the best possible chance to get a reasonable harvest.

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What else can you do to improve your harvest?

If you have limited choices on where you place your tomato plants you can also look at other factors which will help to maximise your yield. The most obvious thing that you can do is placed the tomatoes in the warmest possible location which can ideally be next to a south facing brickwall as this will radiate heat out and increase the temperature around the plant.

If you do not have a brick wall available in the sun then you can also place large stones around the plant which will help to radiate heat at night-time to maximise growth rate.

When is the best time to plant tomato seeds

To optimise the size of your harvest the best time to plant tomato seeds is around 4 to 6 weeks prior to the last frost. The reason for this is that it will it will ensure that tomato seedlings have a reach a reasonable size and are ready to be planted out as soon as there are frost-free conditions outside.

When planting out the tomato seeds it is best to sow the tomatoes in a modular seed tray and fill it with seed raising mix. To ensure that it is easy to transplant the tomato plants later on it is important to firm the soil into the modules to form a solid plug.

To ensure that you have at least one plant in every cell plant 2 to 3 seeds per cell at a depth of approximately half an inch. Place the seed tray in a warm location to germinate and if more than one seedling appears in a cell select the strongest seedling to grow on and remove all of the other ones.

For tomato plants to germinate they ideally need temperatures of between 15 or 20C. In these conditions they will take around 7 to 10 days to emerge and a further 4 to 6 weeks to reach a sufficiently large size but they are ready to be transplanted out into the garden.

Planting seedlings out in the garden

Once the weather has got sufficiently warm it is important to erect a structure to support the growth of the tomatoes. The easiest structure to use to support tomatoes is a trellis as they’re quick and easy to erect and relatively tall. 

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The next important step is to prepare the soil by adding additional compost which will provide sufficient nutrients for the plant throughout the growing season. Once the structure is in place and the soil is ready then plant the tomatoes at the base of the structure and water them in well.

Caring for tomatoes throughout the season

When the tomato plant has been established for a few weeks it will be necessary to start to maintain it by tying the plant regularly into the support structure and removing any side shoots which are the shoots that will appear on a 45-degree angle between the main stem and the leave branches.

These side shoots can be pinched out using your thumb when they are very small which will help to maintain the plant and keep it focused on producing fruit rather than foliage.

Typically, fruit will not ripen until the plant is between 80 and 120 days old, however, that is dependant upon the weather conditions in your particular region. Once the tomato plants begin to produce fruit it is important to pick it regularly to encourage the plant to continue to produce flowers and therefore more fruit.

This cycle can continue up until around 4 weeks prior to the first frost at which point we recommend that you remove the head of the plant as this will to ensure that it focuses on ripening the fruit that is already has rather than trying to produce new fruit that will not ripen.

Once the weather begins to deteriorate the final harvest of any remaining green Tomatoes should be taken from the planet. These green tomatoes will be able to be ripened on a window sill or in a fruit bowl with an ethylene producing fruit such as bananas provided that the tomato is sufficiently developed.

Generally, tomatoes smaller than a marble, for a regular slicing tomato, will usually not ripen at all, however these fruits can still be used to make up sauce or chutneys to make sure you get the most out of your tomato plants. 

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