How to grow watermelon in a greenhouse

How to grow watermelon in a greenhouse
How to grow watermelon in a greenhouse

Did you know that among the various greenhouse crops, the last place is not occupied by watermelon? So how to grow watermelon in greenhouse? This article will take you through it.

Of course, this type of cultivation is not for production purposes and is not grown in the south, but it shows very good results and quite meets the tastes of brave owners.

However, there are certain differences between the agricultural techniques of greenhouse growing and open field growing, and you need to know the specifics before growing watermelon in a greenhouse.


In mid-April, it’s time to plant watermelon seeds. To do this, prepare small, preferably peat pots of 10cm (3.93inch) diameter and a nutrient-rich soil mixture (add potassium sulfate and wood ash to the existing soil).

Place 1-2 watermelon seeds soaked in warm water into each glass until 2-3cm (0.78-1.18inch) deep and place on a south window.

Although seeds germinate at temperatures above 17°C (62.6°F), indoor temperatures should be between 25 and 35°C (77-95°F) during the day and between 18 and 20°C (64.4-68°F) at night for efficient plant formation.

For the entire growth period of watermelon seedlings, it is best to make one, preferably two, fertilization applications using a mineral fertilizer complex, the first of which should be made two weeks after sowing.

As the plants grow, the pots are moved away so that the seedlings do not come into contact with each other and the leaves. Once 3-5 true leaves have formed on the young plants, they can be planted in the greenhouse. This usually occurs after 25-35 days.


Watermelons can be planted in mid-May if the greenhouse is heated, but if not, it is worth waiting until the outside stable temperature reaches 20-25°C (68-77°F).

Seedlings are planted in pre-prepared monopolies, 40-50 cm (15.7-19.6inch) apart from each other, 20 cm (7.87inch) high, and 40-50 cm (15.7-19.6inch) wide. In this case, the plants are not buried.

An important nuance is the height of the greenhouse and the humidity level maintained in it. For the comfort of watermelons, the humidity indicator should be kept at 60-70% and the height of the greenhouse roof should be 1.8-2m (5.9-6.5foot).


Due to the long fibrous roots of watermelons, they must be tied up. Therefore, you will need to wrap the weedy ends of the plants counterclockwise around the lattice as you walk around the bed each day.

Also, in greenhouse cultivation, watermelons are formed one stem at a time, so any watermelons (side shoots, flowers) that form to a height of 40cm (15.7inch) should be pulled out.

Sixty days after planting, the plants start flowering. The first to appear on them are male flowers, and 10 days later – female flowers.

During this period, it is very important to perform pollination. In areas with a warm climate, for this purpose regularly open the windows of the greenhouse, giving the opportunity to do their work insects, in northern regions, pollination is performed manually.

To do this, it is necessary to pluck the male flowers and connect their stamens to the female flowers. How to distinguish between male and female flowers? A small watermelon flower may be seen first on the female flower.

If it has been pollinated, the ovary will start to grow and bend downwards, if not – the flower will stretch upwards. Here, too, you have to pay attention.

And when the watermelon starts to grow to the size of a plum, count 7 leaves up from each leaf and cut off the top of the stalk. If only one fruit is ripening on a plant, it is best to consider the selection, and if there are several berries on the stalk, the harvest will be small.

When the watermelons reach tennis ball size, place a grid on each one and tie it to the top trellis. If this is not done, the plants will drop in weight from growth. Within a month after the ovaries are formed – you can harvest.

One more thing, the leaves of watermelons do not thin, their cut structures do not shade the fruit, but the constant appearance of side shoots strongly delays the moment of ripening – they are periodically pulled out.

In addition, watermelons do not like weeds growing on their roots, so it is important to monitor the cleanliness of the greenhouse.

Also, if the fruit is formed at the base of the stem – not tied, but laid on the ground – a board should be placed under the watermelon, otherwise, it is likely to cause its rotting.

Greenhouse watermelon care
Greenhouse watermelon care


Despite the common belief that watermelon likes to be watered, it is actually a drought-tolerant plant and it needs to be watered very carefully.

It needs water most during the first period of growth, before and at the beginning of flowering.

It is best watered with warm water, 10 liters per 8-10 plants. And when the fruit reaches the size indicated in the variety description, watering stops immediately.

It is good to carry out and fertilize at the same time as the weekly watering. To do this, you need to mix 1 tbsp of nitrogen, phosphorus, and potassium, 1 tbsp of superphosphate, 1 tbsp of potassium sulfate, and 2 tbsp of any micronutrient fertilizer.

Fertilize no more than 4 times in total, just until the berries reach variety size.

Title: How to grow watermelon in a greenhouse
Source: ThumbGarden
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