Pumpkins are grown mainly in northern Victoria, with smaller plantings in the southern vegetable growing districts. Pumpkins are summer-growing annuals and will not tolerate frost.
Pumpkins may be grown on a wide range of soil types providing the soil is free-draining. They are tolerant of fairly acid conditions and liming should not be necessary unless the pH is less than 5.5.
Well-drained soils that warm rapidly in spring are ideal for the production of the quick-maturing pumpkins of the Windsor Black and Butternut types. Friable loams with an abundance of organic matter and the capacity to retain moisture are ideal.
Prepare a deep, friable seedbed. Early soil preparation will allow time for cultivations to help eliminate weeds.
Sowing of early pumpkins for marketing in December starts in September in northern districts. The main crop is sown from mid-October until Christmas. Pumpkin seed needs a minimum soil temperature of 15°C to germinate and this will determine planting time.
The application of 30 cubic m of fowl manure per ha benefits areas prepared without a cover crop. Apply a base dressing of 600 kg to 1000 kg of N:P:K 5:8:4 or 6:6:6 per ha, or the equivalent, before planting.
Sow directly into the field. Thin crops drilled mechanically in rows to one or two plants when established. If mechanical seeders are not available, sow the seed by hand in clumps at the desired spacing.
Space the rows between 1.5 m and 2 m apart and space the plants around 1 m apart in the plant row for the largervined pumpkin. Butternut pumpkins can be planted on double rows on beds 1.5 m wide or spaced to 450 mm between plants. Wider spacings are recommended in areas where irrigation is not used.
A pre-emergent herbicide is now available for use in pumpkins for some broadleaf weeds. However, cultivation for weed control may still be important for some weeds and must be regular and effective from the time the young plants emerge. All weeds must be under control before the plants produce runners because cultivation must cease at that stage. There are also selective herbicides available for control of grass weeds within a crop. For registered chemicals see your local supplier or the website of the Australian Pesticides and Veterinary Medicines Authority (APVMA)
Plan plant and row spacings according to the cultivating equipment available so that mechanical cultivation can be the main means of controlling weeds.
Early pumpkin flowers are difficult to pollinate if the weather is cold, wet or windy during flowering. To aid fruit set, place five or six beehives per ha through the crop at the start of flowering.
Bees will also be killed by a number of pesticides that may be used and care should be taken when spraying for pests or diseases. The apiarist should be consulted before spraying and if it is necessary, only sprays of very low toxicity to bees should be used and applied at evening.
Control of pests and diseases
Key pests of pumpkin and kubocha crops include; pumpkin beetle, leafhoppers and aphids. There are pesticides available for their control and in particular there are targeted chemicals available which will fit into an Integrated Pest Management program.
The major disease of pumpkins is powdery mildew, which will tend to occur in late summer autumn in response to dewy nights. At this stage if fruit have reached full size and are close to harvest it is not a major issue. If fruit have not sized fungicides may need to be applied alternating protectant and systemic fungicides. If powdery mildew is a regular problem use resistant varieties.
Other diseases include downy mildew, anthracnose, gummy stem blight and the soil disease Fusarium species. For Fusarium root and crown rot it is important to ensure good drainage of soil and avoid over-watering.
For descriptions of these pests and diseases see the "Field Identification Guide – Pests, Beneficials, Diseases and Disorders in Cucurbits;" produced by the NSW Department of Primary Industry.
There are chemicals registered for control of these pests and diseases and they are sold under various trade names. Follow the label for directions before use. Contact your chemical supplier or the Australian Pesticides and Veterinary Medicines Authority website will provide you with a current list of registered chemical that can be used on zucchini.
Early pumpkins are harvested when the outer skin has coloured and is reasonably hard and are marketed immediately to catch the high prices of the early season. Withering of the stem indicates full maturity.
Pumpkins for storage are best left in the field until the vine withers. Remove the fruits from the vines, taking care to leave 50 mm to 75 mm of stem attached. Reject fruit for storage if the stems are accidentally broken off as rot organisms will enter at this point.
Yield of pumpkins ranges from around 20-40 tonnes per hectare and for butternut pumpkins 10-25 tonnes per hectare. Yields tend to be higher in the northern production areas.
Pumpkins for storage must be sound and should be handled with great care. Any bruise will soon develop a rot, which can spread through the stack. The ideal storage is a rat proof shed, built well off the ground, preferably at the level of a motor truck tray. Provide plenty of shelves to allow free circulation of air inside the shed.
In areas not subject to severe frost, pumpkins can be stored satisfactorily under heavily-foliaged cypress hedges, but for long storage pumpkins must be stored at temperatures above 7°C or breakdown caused by cold damage will occur.
Most growers sell their pumpkins in bulk, by the kilogram. Butternut pumpkins are usually sold in 20 kg red net bags or fibreboard cartons
Table 1. Main pumpkin cultivars (varieties)
Cultivar Description/shape Maturity Weight Remarks
Butternut Pear-shaped (Waltham Strain), oblong, block (Large Butternut) 3 to 3.5 months 0.75 kg to 2 kg Thrives best in warm conditions and situations. Mid-season to late variety. Sold by the bushel case.
Windsor Black Parallel sides with a cap 4 to 5 months 7 kg to 14 kg Popular mid-season pumpkin, Stores better than Butter Pumpkin.
Queensland Blue Parallel sides 5 months 4 kg to 7 kg Standard, long-storing pumpkin.
Jarrahdale Thick, flat, semi ribbed 5 months 4 kg to 8 kg Currently most popular variety. Good storing pumpkin.
Sweet Grey Thick, flat, smooth with slight rib 4 to 5 months 4 kg to 6 kg Excellent quality, high yielding, very good storage.