Hokkaido pumpkin: planting, harvesting & uses
Hokkaido pumpkins are also commonly known as uchiki kuri and they are becoming increasingly popular among vegetable growers in the UK.
The Hokkaido pumpkin (Cucurbita maxima) is a highly healthy pumpkin that is simple to grow. They are also smaller in size than other types of squash, making them ideal for smaller households. Learn how to grow, harvest, and store these superb pumpkins.
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Origin and properties
The Hokkaido pumpkin is a thin-skinned winter squash with orange flesh, originating from the Japanese northern island of ‘Hokkaido’. It is thought that Americans brought squashes to the island in the 19th century, and they were bred to achieve the Hokkaido’s more intense flavour. A Hokkaido pumpkin is known by many names, including the ‘chestnut squash’ due to its nutty taste. In Japan, it is known by the name ‘uchiki kuri’ and that term is becoming more and more commonly known in the UK. You can now see squashes sold as a ‘uchiki kuri’ variety in many seed catalogues.
It is an annual plant that belongs to the pumpkin family (Cucurbitaceae) that produces orange-red fruits in a teardrop-like shape. A Hokkaido pumpkin plant often produces two to three fruits, with each one typically being 15cm in diameter and weighing from 0.5 to 2.5kg. The flesh is yellow-to-orange in colour. The plant sprawls and climbs, often reaching 3 to 4m long, and it has large dark-green foliage. Hokkaido pumpkins produce yellow funnel-shaped flowers that bloom in early summer.
Varieties of Hokkaido pumpkin
There is a range of sweet and nutty-tasting Hokkaido pumpkin varieties available to growers in the UK. The majority have orange skin, however, there are some blue and green-skinned varieties that are popular in Japan.
Here are some of the most popular Hokkaido pumpkin varieties:
- ‘Amoro‘: orange skin with light stripes; heart-shaped; thin-skinned and tender fruits; high yields of early-ripening fruit.
- ‘Blue Ballet’: blue-green skin; lower yields of aromatic, nutty, medium-sized fruits; medium-to-late ripening.
- ‘Blue Kuri’: also known as Blue Hokkaido; thicker, blue-grey skin; high yields; vary in size; early maturing.
- ‘Green Hokkaido’: dark green shell; long shelf life; fine aroma with medium-sized climbing fruits rather late maturing.
- ‘Red Kuri‘: a red kuri squash has smaller orange-skinned fruits that are medium-late ripening. Regularly sold under the name ‘Uchiki kuri’ on seed packets.
Planting uchiki kuri
Hokkaido pumpkins should only be sown directly in the bed or planted outdoors after the last frosts from mid-May onwards. Due to their long growing season, they are predominantly sown indoors early and planted out after the risk of frosts has passed. They like very nutrient-rich soil and are heavy feeders. To enrich the soil, add some garden compost or well-rotted manure to the site prior to planting. You can use our Plantura Organic All Purpose Compost for this; as it is peat-free and made of organic plant fibres, it will provide Hokkaido pumpkin plants with all the nutrients needed for strong and healthy growth.
- Perfect for all your house, garden & balcony plants
- For strong & healthy plants as well as an active soil life
- Peat-free & organic soil: CO2-saving composition
Growing Hokkaido pumpkins indoors:
- Sow seeds indoors from April onwards
- Sow seeds individually in pots
- Sow the seed on its side 2-3cm deep and cover with compost
- Water well and keep the soil moist
- Germination temperature: 20 – 24 °C
- Germination takes between 8 and 14 days
- Harden young plants off outdoors in May
- Plant outside after the last frosts
- Allow a good 1.5m between plants
Sowing uchiki kiri seeds directly outdoors:
- Sow seeds outdoors after last frosts have passed
- Sow the seed on its side 2-3cm deep and cover with compost
- Water well and keep the soil moist
Plant care
Water young Hokkaido pumpkin plants in well and keep watering during the summer to help the plants to grow and fruits to swell. Regular feeding with a liquid fertiliser every 2 to 3 weeks will benefit the plants as they grow. Keep the area weed-free as the plants grow – this is vital until the plant sprawls enough to start smothering the ground. A layer of mulch around the plant can help to reduce weed competition and to maintain moisture in the ground.
Pinch out excess shoots or shorten tips in July to help ensure the largest squash possible. Remove the growing tip once three fruits have set; this will boost their chances of ripening. When Hokkaido pumpkins are starting to develop on the plant, start removing foliage that is covering the fruit to help more sun to reach the squash and help it develop its full colour. Place the fruit on wood, bricks or tiles to prevent the fruit from sitting on wet soil and stop pests from nibbling on them.
Take care to not splash the leaves when watering to reduce the risk of downy mildew (Peronospora) but keep the root area moist as roots that are too dry will have an increased risk of powdery mildew (Erysiphacae).
Tip: check out our pumpkin plant care to discover all there is to know about caring for pumpkins.
Harvesting Hokkaido pumpkin
Leave the fruits on the plant as long as possible to give them the best chance of fully ripening. However, they must be harvested before the first frost, as they are very sensitive to frosts. Hokkaido pumpkins are generally ready for harvest about 95 to 120 days after sowing. A good tip to check they are ripe is to tap the fruit. If you hear a hollow noise, that is a good sign the squash is ripe. Another indicator is that the stem should be woody and dry and the skin hard to the touch. A Hokkaido pumpkin needs to be fully ripened if it is to store well over winter.
The harvesting time for Hokkaido pumpkins is usually between September and November. When they are ready to be harvested, carefully cut the fruit off the plant taking as much of the stalk as possible. Once a Hokkaido pumpkin has been cut from the plant, it needs at least 10 days to cure before being ready for storage. This can be done in the full sun outdoors, or the squash can be brought into a greenhouse, polytunnel, or cold frame to cure. Anywhere the Hokkaido pumpkin can get warmth and light without getting wet is ideal. For more tips and tricks on harvesting pumpkins, check out our feature article.
How long does a squash red kuri keep for?
If a Hokkaido pumpkin is stored properly, it can last for up to 6 months over winter. Once the pumpkin is well cured, store it in a dry place at a temperature between 12 and 15 °C. If the temperature goes below 10 °C, there is an increased risk of storage rot; never store your Hokkaido pumpkins where there is a risk of freezing. Do not stack the pumpkins and regularly turn them to prevent them from spoiling. Any Hokkaido pumpkins that start to show signs of rot should be removed so as not to affect other fruits. The fruit can be cut into pieces and frozen both raw or cooked, however, any defrosted pumpkin turns out soft. Frozen Hokkaido squash can be kept for up to a year. Other options for preserving the pumpkins include boiling, pickling or processing them into jam.
Uses and nutritional benefits
The Hokkaido pumpkin has many health benefits, as it contains a lot of vitamins and minerals, including vitamins B, C, and E. The fruit is also a good source of potassium, magnesium, iron, folic acid and phosphorus. There is a wide range of uchiki kuri recipes, with the fruits regularly used in soups, stews and casseroles. It also tastes great oven-roasted or made into gnocchi. Sweeter options include pumpkin pies and cakes.
Butternut squash is another really popular squash that is very versatile in the kitchen and simple to grow. Find out all the information you need to grow butternut squash in our dedicated article.
