Pumpkins: planting, fertilising & harvesting

Alina
Alina
Alina
Alina

For many years now, I have been growing various vegetables as a hobby in my spare time, which is what ultimately led me to studying horticulture. I find it fascinating to watch as plants grow from seed to fruit and to then finally be able to make use of the literal fruits of my labour.

Favourite fruit: Strawberries and cherries
Favourite vegetable: Potatoes, tomatoes and garlic

Pumpkins are currently a popular vegetable in the kitchen. This article will give you a good overview on what is important for successfully growing your own pumpkins.

pumpkin in garden
Pumpkins take quite some space in a garden bed [Photo: Peter Turner Photography/ Shutterstock.com]

The cultivation of pumpkins (Cucurbita) at home is becoming more and more popular in Europe. In autumn you can buy the gorgeous vegetables in all colours, shapes and sizes. Pumpkins originally come from America and are one of the most diverse vegetables of all. In addition to their large fruit, pumpkin plants are also appreciated for their striking yellow flowers and tasty pumpkin seeds. What is more, in milder latitudes growing pumpkins can be very fruitful when cared for properly.

Despite the exotic origin of the vegetable, pumpkin cultivation in Europe is generally successful and you can expect high yields. In order for your pumpkin project to go smoothly you should follow a few tips, as explained below.

The ideal location for growing pumpkins

Pumpkins require specific location conditions. Depending on the pumpkin variety, the plant may spread 1.5 to 2 m² across the bed. Many varieties also climb up and twine during growth, such as the popular Hokkaido pumpkin (Cucurbita maxima). A climbing aid can be helpful for smaller pumpkin varieties. Or you can choose a location next to a fence for the pumpkin plant to climb, for example. Larger pumpkins should stay on the ground due to their weight.

Pumpkins are warmth-loving plants. The location should therefore be sunny and sheltered from the wind. It is vital for the ground to warm up early. Light to medium soils rich in humus and with good water storage such as sandy loam are the best option. Acidic soils do not offer good conditions for growth; the pH value should be at least 6. When choosing the location, it is particularly important to pay attention to crop rotation: pumpkins should never be planted after other cucurbit or gourd family plants (Cucurbitaceae). Gourd plants include (next to pumpkins) courgettes, cucumbers and even melons. Potatoes, legumes (Fabaceae) and cabbages, on the other hand, are great as previous crops.

Location tips for pumpkins:

  • Allow plenty of space (1.5-2 m²) and an opportunity for vines to climb
  • Sunny and wind-protected location
  • Light to medium soils (e.g. sandy loam/loamy sand)
  • High humus content and water retention capacity
  • Acidic soil is a no-no (pH value > 6)
  • For previous crops avoid gourd plants (Cucurbitaceae); preferable predecessors are potatoes, legumes or cabbage instead

Remembering these tips when planting pumpkins will allow them to grow effortlessly and bear a number of scrumptious fruit.

Pumpkin varieties

The variety of pumpkins is remarkable – in fact, more than 800 pumpkin species are known. Pumpkins come in all imaginable shapes, colours and tastes. The species cultivated in Europe, however, are largely limited to three: giant pumpkins (Curcurbita maxima), which include the popular Hokkaido pumpkin, Curcurbita moschata varieties, such as Butternut pumpkins or Muscat de Provence, and Cucurbita pepo, which includes the subspecies summer squash.

A small overview of the most popular varieties:

  • Uchiki Kuri: Hokkaido type variety with small onion-shaped fruits; smooth, bright orange skin; the orange-red flesh tastes delicious, similar to chestnuts.
  • Muscat de Provence: a particularly aromatic pumpkin; flat, deeply ribbed fruits with light orange/brown skin; the firm flesh has a strong orange colour and is very tasty; the variety also stands out for its long shelf life.
  • Vegetable spaghetti: bears elongated oval fruits with pale orange colour and light flesh; Italian variety.
  • Atlantic Giant: giant pumpkin variety; can produce record weights (breeder Dill won several records with this variety, e.g. European record 2009 with approx. 650 kilos); yellow flesh of the light orange fruits is very tasty; suitable for preserving.

Planting pumpkins

Pumpkin plants are low maintenance. Nonetheless, they are sensitive to low temperatures due to their warm origin. There are two methods for growing pumpkins:

new pumpkin shoot in a pot
New pumpkin shoot in a pot BU: Pre-growing pumpkin plants in pots is helpful [Photo: Dajra/ Shutterstock.com]

Growing from seed: pumpkin seeds are not sown until mid-May, after the last frosts of the Ice Saints (11th to 15th of May) have passed. Temperatures below 5 °C will damage the young plants. Germination starts when it is a bit warmer at about 14 °C. The perfect depth for sowing is 2-4 cm. Sow the seeds at a distance of 0.5-1.5 m and 1.5 m between the rows.

Pre-culture: Alternatively you can pre-grow the seeds in a pot starting already in April. Then you can plant the young plants into the garden bed from mid-May. When growing in pots, place one seed in each pot about 2-4 cm deep. Ideal temperature for germination is 20-24 °C. As soon as the first one or two leaves grow off of the stem and frosts have passed, you can plant them into the garden bed as described above

But, which of the two methods works better? That depends on the location. In cooler regions pre-cultivation in pots is definitely safer! In addition, you can expect an earlier harvest with this method. It is also worth covering the young pumpkin plants with fleece at the beginning of the season to protect them from late frosts. Also protect plants with fleece before the flowers form so that pollination can take place unobstructed.

Caring for pumpkin plants

All in all, the care of pumpkins is not very time-consuming. Here are some useful tips with regard to pumpkin care:

Watering pumpkins

Regular watering is essential for pumpkin plants. This is particularly important when fruit is forming, otherwise the harvest will be smaller. When watering, always water directly on the ground without getting the leaves wet, as that promotes risk of rot. This can also occur with pumpkins lying directly on the ground. Use a base (for example a board or an upside-down pot) to lift the fruits from the ground.

Fertilising pumpkins

Pumpkins require a lot of nutrients; therefore, regular fertilisation is advisable. Before sowing or planting, prepare the soil with compost. During the growing period it is recommended to fertilise once a week. You can use nitrogen-rich fertiliser mixed into regular water supplies.

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As pumpkin plants grow quickly and develop large leaves, weeds will struggle to grow. Young pumpkin plants however give way to weeds. Therefore, you should make an effort to regularly remove weeds, especially at the beginning, so that the plant has enough light, nutrients and water to grow.

Cutting back pumpkin plants and scarification

A popular method in pumpkin plant care is the removal of new shoots. General rule of thumb: the more fruits grow, the smaller they become. It can therefore be worthwhile not to let all of the fruits grow, so that the rest get enough energy and nutrients. You can start cutting off unnecessary side shoots starting in June. Shoots with 3 to 5 leaves are shortened above the second leaf. Repeat pruning round in July, but only above the fifth leaf. After all female flowers have been pollinated (see fruit set starting to form at the base), you can remove the male flowers. This also gives the plant more energy for fruit formation.

young pumpkin plant in a pot
Young pumpkin plants should only move outdoors after the last frost (Ice Saints) [Photo: NOPPHARAT789/ Shutterstock.com]

Tips for taking care of the pumpkin plant:

  • Regular watering
  • Do not wet the plant’s leaves and fruit when watering in order to avoid rot
  • Before planting, work compost into the soil
  • Fertilisation during the growth phase once a week with nitrogen-rich fertiliser (mix into irrigation water)
  • Regular weed removal (especially for young plants)
  • Prune any unnecessary side shoots

Pests and diseases

Usually the weather has the biggest influence on the yield. Heavy damage can be inflicted by hail, for example. Additionally, diseases and pests can make it difficult to grow pumpkins in your garden. A particularly unpopular guest are slugs. Especially in rainy springs slug population may become a bigger problem. Collecting the small animals helps, but unfortunately they are sneaky enough to come out at night for feeding. You can try spreading coffee grounds between the plants as slugs will avoid that.

yellow pumpkin flower
Yellow flowers are typical for pumpkin plants [Photo: Peter Turner Photography/ Shutterstock.com]

Another risk with pumpkin plants are fungal infections. One problem can be powdery mildew, which you can recognize by a floury-white coating on the surface of the leaves. Infection with the Didymella bryoniae fungus can also occur at very hot temperatures. The fungus causes what is known as stalk burns, which manifest themselves in brown leaf spots, necrosis and rubbery stalks.

Tips to prevent fungal infections:

  • Avoid damaging the plant at all costs
  • Do not wet the leaves during watering
  • Do not overdose the plant with nitrogen fertiliser
  • Do not let the vegetation grow too dense

There is no one hundred percent protection against pests and diseases. In the case of fungal infestation, affected plants can be sprayed with a mixture of sodium bicarbonate, vegetable oil and curd soap. At an advanced stage, especially with an infected stem, the plant should be completely removed from the bed to prevent further spread of the disease. If these instructions are followed, the risk can be reduced and a good pumpkin harvest can still follow.

Harvesting and storing pumpkins

When summer is coming to an end, it is time for the harvest of pumpkins. This allows the healthy vegetables to be used in time for Halloween and the cold season.

pumpkin growing in a garden
Orange is the colour most people associate with pumpkins

Harvesting

Depending on the variety, pumpkins start ripening mid-August at the earliest. However, most varieties are harvested between September and October. Harvesting before the first night’s frost is recommended. These characteristics determine if the pumpkin is ready for harvest:

  • Intense colour (easy to recognise, especially with orange-red varieties such as the Hokkaido)
  • Wooded and dry stalk
  • Leaves dry and die off
  • Scratching the shell with the fingernail leaves no mark
  • Hollow sound when knocking the fruit (does not apply to all varieties!)
harvested pumpkin
The pumpkin is ready for harvest when the stalk turns woody [Photo: JohnatAPW/ Shutterstock.com]

Dry weather is best for harvesting pumpkins.That way they can dry outdoors for 2 to 3 days. To harvest the pumpkin, separate the fruit from the stalk with a sharp knife.

Tip: Some of the stalk should remain attached to the pumpkin! This makes it harder for diseases to penetrate the fruit and the pumpkin will last longer. On the whole, it is important to be very careful when harvesting the pumpkin, as damage to the fruit can lead to rot.

Storing pumpkins

In general, the pumpkins you grow yourself can be in storage for a relatively long time provided that they are stored correctly. After harvest, pumpkins need a ripening period of about 3 weeks at 20 °C in a light and dry place. It is important for the pumpkin to lie on a dry surface such as wood or cardboard and is turned regularly. Post-ripening improves the pumpkin’s taste and increases the germination capacity of the pumpkin seeds, which can be reused next year.

Pumpkins can then be stored for up to 6 months, depending on the pumpkin type and the way they are stored. A dry and dark place is perfect with temperatures between 12 and 15 °C. Lower temperatures can lead to rot, higher temperatures can have a negative effect on the taste.

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