How to grow a giant pumpkin?
People often ask me the question: how do you grow such a giant pumpkin? On this website, I will explain how you can easily grow a pumpkin of 100 kg. With a little extra attention, it is even possible to grow a pumpkin that weighs more than 600 kg from your own garden.
Atlantic Giant is the variety from which these giants grow and there are many different seeds available from this variety. I started with a few seeds from the local garden shop, but the results were disappointing. When I managed to get hold of a seed from the Dutch champion, I immediately achieved weights more than 100 kg. These seeds are significantly larger than the seeds offered for sale at the local garden shop. Larger seeds result in faster germination and the larger cotyledons will ensure a good and vigorous start.
Before the seed is planted, the ground has to be made suitable for growing giant pumpkins. A pumpkin plant prefers a loose and fertile soil. Therefore, I will start in October with mixing horse manure in the soil. In addition, I have planted African Marigolds as a cover crop. When the whole vegetable garden is ploughed, I apply worm manure on top, which will be raked through the loose soil together with Plagron’s Supermix and Calcium Kick. To ensure that the roots can grow well and absorb sufficient nutrients, I use walking boards to keep the soil loose.
I start sowing in mid-April. A pumpkin plant cannot tolerate frost, it must be grown in a greenhouse until at least the second half of May. Before I plant the seeds, I carefully sand the edge off, so that the seed casing can burst open more easily and gets easily from the leaves. Be careful not to sand the whole edge, the pointed side of the seed should not be sanded, because this is where the root will develop. After thinning the edge, I pre-soak the seeds in lukewarm water for eight hours, then plant them in a 2-5 litre pot and let the plants germinate at room temperature (25 degrees Celcius is the optimal temperature). When the plants have germinated, it is important that the temperature and amount of light are in proportion, because this will prevent the plant from sprouting too much.
From the moment the two cotyledons of the plant are fully grown (about 8-10 cm) and the third leaf begins to form, the plant can be planted in the ground. The third leaf, the first true leaf, indicates the opposite growth direction of the main stem of the plant. Besides frost, the plant is not resistant to hail and high winds. The plant can for example be raised in a greenhouse, or you can plant the pumpkin in a wind-free spot. However, this is not necessary. In the Netherlands it is even possible to grow a pumpkin of more than 600 kg in the open air. Because the plants need a lot of nutrients, I start adding terra grow from the moment the plant is in the ground and I gradually increase the amount of added fertilizer.
Each leaf creates energy for the pumpkin’s growth, so it is important to grow a plant of 50 to 100 square metres. A smaller plant is possible, but this will result in a smaller pumpkin as well. If you have limited space or don’t want to spend so much space on one pumpkin plant, growing a giant tomato is a nice alternative, because you can grow it in a pot. To ensure that the pumpkin plant quickly reaches the right size, I guide the main vine and the side vines. At every leaf a new vine and a tendril will be formed. The branches that grow out of the side branches, called tertiaries, are removed. When the plant has reached the right size, I will pinch all the growing buds so that all the energy which is produced will go to the pumpkin. Thereby, in the axillary bud, a leaf, a flower and two roots will be formed. To ensure that the plant can absorb sufficient nutrients, I cover the leaf axils with soil to stimulate root formation. The plant will need a lot of water, so it is important that the plant has sufficient roots.
I let the pumpkin grow on the main vine when it reaches about six metres. There are two types of flowers on the plant: male and female flowers. The female flowers can be recognised by the little bulb underneath the flower, which will grow into a pumpkin. To make sure that pollination goes well and that there is no cross-pollination, I remove a few male flowers from the plant and use them to pollinate the female flower. To prevent cross-pollination, it is important to close the flowers, so that no pollination can take place by insects or the wind. When there is one pumpkin about the size of a football at about six metres from the stem, I remove the rest of the pumpkins to ensure that all the energy goes to one pumpkin. To prevent the pumpkin from rotting, you can grow it on a pallet. To prevent the pumpkin from ripening too early, I cover it with a bedsheet. Because the pumpkin grows so large, it can tear off the stem. By carefully placing the main vine in a s-position and placing the pumpkin carefully away from the main vine, this will be less likely to happen. From this moment on I stop using terra grow and start using terra bloom. Are you curious about the weight of the pumpkin? Click here.
Insects and diseases
When the plant has only its cotyledons, it is very vulnerable to snail damage. This will be over when the plant has formed its first five true leaves. From this moment on, the plant will be more susceptible for aphids. Mildew is the most common disease on the pumpkin plant. This can have a major negative impact on the growth of the pumpkin. Mildew will spread itself quickly over the whole plant, especially in warm and humid weather. A healthy plant is less likely to suffer from this and therefore the right amount of nutrition and water is important. It is also possible to prevent mildew from developing. This can be done both conventionally and organically. For a biological prevention, I spray a mixture of 60% water and 40% milk over the leaves every week. Under the influence of sunlight, the milk will be converted into acids. Acids have a negative influence on the growth of fungi. I also remove the sick and old leaves to prevent spreading of the disease.
Growing giant pumpkin still means dealing with nature. Because extreme demands are asked from plant and the pumpkin, things can easily go wrong. The pumpkin can grow so fast that it literally explodes. The weather also plays an important role. A hailstorm can destroy the whole plant or a wet summer can cause the stem of the plant to rot. To be sure of a good harvest, I grow a few plants under different conditions. For this reason, I grow a few in a greenhouse and a few outdoors to spread my chances.
Giantpumpkins.nl is dé Nederlandse website voor het kweken van reuzenpompoenen en andere supergroenten. Een aantal jaren geleden ben ik begonnen met het kweken van pompoenen in een moestuin. Naast verschillende soorten en vormen die er te kweken zijn, zijn er ook veel verschillen in grootte. Na het zien van de Atlantic Giant op de verpakking van een van de pompoenzaden wilde ik ook een reuzenpompoen kweken (lees verder).