Pumpkins Technical Information
Introduction
All pumpkins are members of Cucurbitaceae (gourd family). Botanically there is no distinction between squashes and pumpkins since both pumpkin and squash cultivars are found in these species:
A Pumpkin can be a - pepo, maxima, moschata or mixta.
Pumpkins originated in the Americas and were cultivated by the ancient civilizations of Central and South America over 7000 years ago.
Pumpkins are the edible fruit of any species of curcurbita (usually C. pepo) utilized for Halloween, livestock feed or in pies. The flesh is somewhat coarse and may be strongly flavored and is not generally served as a baked vegetable.
Pumpkins are warm season crops which are both cold weather and frost sensitive. They are more cold hardy than cucumbers. The minimum temperature for seed germination is 15℃, with a maximum of 38℃ and an optimum range of 20 to 32℃.
Best crop growth occurs at 18 to 25℃, with a minimum of 10℃ and a maximum of 32℃. Cultivars requiring a long growing season should only be planted in the regions where grain corn can be grown in fields which are sheltered since cold winds are detrimental to growth. Plastic tunnels, row covers and/or plastic ground mulches benefit these crops. Well drained loams well supplied with organic matter are optimal for early production.
Nutrient Content: Excellent source of Vitamin A; good source of Vitamin C; potassium and calcium. Low in sodium. The seeds are a good source of protein, contain some iron and are high in unsaturated oils. Some cultivars are being grown for the seed or pressed for oil. Due to the high vitamin A content of pumpkin and squash flesh, consumption will reduce the risk of cancer and heart disease.
Crop Establishment
Seeding/planting - Do not plant until the soil temperature is at least 16℃.
| Between Row | Within Row | |
|---|---|---|
| Bush or Vine Trees | 1-1.5m | 1-1.5m |
| Small Fruit and Large Vine | 2-3m | 1-1.5m |
| Large Fruit and Large Vine | 2-3m | 1-1.5m |
For vine types 2 to 5 kg per hectare and bush types 4 to 6 kg per hectare. Space rows 2 to 2.5m apart for pumpkins and hubbards, and 1 to 1.5m apart for bush pumpkins. Plants should be spaced at 1m for pumpkin and hubbards, and 0.6 to 0.9 m for bush pumpkins. The depth of seeding should be 25 to 30mm. For transplants seed two to four weeks before field setting in individual containers such as peat pots, peat blocks or peat pellets. Some growers use cellular trays of 24 to 125 cells. The roots must not be disturbed at transplanting or slow establishment will result.
Crop Management
Rotation
3 years from cucurbit to cucurbit is recommended.
MRL Carry-overs
Be aware this plant is 90-95% water and so past residuals and high persistency active ingredients have been reported in even organic fruits.
Pollination
This is an important concern for a good set of high quality fruit. For Pumpkins, fruit set takes place over a 2 to 3 week period. Cucurbit pollen and nectar is not that attractive for hive bees, bumble bees and wild bees take more interest - both are intangible factors to rely on. If there is a nearby improved source of pollen any bees will go there instead, so remove flowering weeds and locate away from any other nearby pollen sources if possible. Inadequate pollination results in poorly shaped fruit as well as excessive blossom drop. One colony of honey bees per acre is suggested to give 1 been per 10 female flowers. Yield increases have been achieved with up to three hives per acre.
Another UK issue, imparted from our breeder, is that for fruit set uniformity the temperature at pollination needs to be stable, if not, then the fruits become distorted.
Foliage Retention & Sugar build-up
This is an important concern that UK growers perceive the end of the crop as the successful powdery mildew invasion to 'clear up' the foliage. Control weeds. It is the last 10 days of curing when the stems are beginning to dry and go corky that leaf area is required to photo-synthesise the final field cure and sugar levels of the variety. Mildew invasion starts around post flowering stage and gradually worsens as the fruit setting is occurring. This is an important stage to retain leaf cover and improve the quality and yield of the plant. So do carry out a few mildew sprays to cover this period - usually August to Mid September. Breeders are selecting for higher sugar level and brix level varieties nowadays. These have improved flavour and holding ability.
Harvest Stage
Skin becomes dull and dry, stem corkiness.
Fertilisation
Do not add or top dress any nitrogen to this crop. It is vital to avoid encouraging vegetative growth as this will encourage the plant to set fruit closer to the crown and earlier, instead of trailing off and exploring a wider surface area to transport its seed, and thus spread as it would in the wild. The plant requires adequate supply of K and Calcium N and P. The best option is to water in at planting, and then give the plants several booster drenches at weekly intervals to cover the dry weather, then completely hold off watering from fruit set so as to induce early ripening and maturity.
Storage and Conditioning
Pumpkins at 10℃ to 13℃ can be held for 2 to 3 months.
Maturity Indices
Immature fruit have a fleshy stem, maturing fruit will have some stem corking, and well mature fruit will have a well corked stem. Internal colour should be intense and typical of the cultivar. The concentrations of the yellow and orange carotenoids generally increase only slightly during storage. Maturity at harvest is the major determinant of internal colour. Immature fruit will be of inferior eating quality because they contain less stored carbohydrates. Immature fruit will have more decay and weight loss during storage than mature fruits.
Quality
Pumpkins should be full sized and well formed with the stem intact. They should be well matured with good rind development typical of the cultivar. Internal quality attributes are high colour due to a high carotenoid content, and high dry weight and sugar and starch contents.
Optimum Temperature - Storage
Pumpkins are very chilling sensitive when stored below 10℃ (50℉). Depending on the cultivar a storage life of 2 to 6 months can be expected at 12.5-15℃ (55-59℉).
High storage temperature (>15℃) will result in excessive weight loss, color loss and poor eating quality.
Optimum Relative Humidity
50-70% with 60% usually considered optimum Moderate relative humidity with good ventilation is essential for optimum storage. High humidity will promote decay. Although 50-70% RH will reduce decay during storage, significant weight loss will occur. For example, mature Kabocha squash lose 1.0 and 1.5% of their fresh weight per week of storage at 12.5℃ (59℉) and 20℃ (68℉), respectively.
Responses to Ethylene
Exposure to ethylene will de-green squash with green rinds. Ethylene will also cause abscission of the stem, especially in less mature fruit.
Physiological Disorders
Chilling injury. Caused if pumpkins and squashes are stored below 10-12.5℃ (50-55℉). Symptoms of chilling injury are sunken pits on the surface and high levels of decay once fruit are removed from storage. Storing fruit 1 month at 5℃ (41℉) is sufficient to cause chilling injury symptoms. Depending on the cultivar, storage for several months at 10℃ (50℉) may cause some chilling injury.
Freezing injury. Can occur at temperatures below -0.8℃ (30.5℉).
Pathological Disorders
Several fungi are associated with decay during storage of pumpkins and winter squashes. Fusarium, Pythium and anthracnose (Colletotrichum) and gummy stem blight or black rot (Mycosphaerella) are common fungi. Alternaria rot will develop on chill-damaged winter squashes. Fruit that are overmature at harvest (>2 weeks beyond optimal harvest date) will tend to have more storage decay.
Special Considerations
Curing. The fruits may have tender rinds when freshly harvested. Curing in the field (with protection from the sun by placing under the leaves) before handling and stacking into bins will help to harden or cure the rind. The recommended storage conditions also favor curing or hardening of the rind.