Jarrahdale, Japanese and butternut pumpkins are annual vegetables in the cucurbit family that includes cucumbers, melons and zucchini. They have vigorous, prostrate vines and produce fruit with a hard shell and yellow to orange flesh.
The traditional large round, slightly flattened, ribbed type of pumpkin (Cucurbita maxima) has strong, round stems, large roundish, not deeply lobed leaves and a round fruit stalk. The main variety is the Jarrahdale type, a selection from Queensland Blue.
Butternuts and Japanese pumpkins (both Cucurbita moschata) have lobed leaves with whitish blotches and angular stems. Japanese pumpkins are less vigorous than Jarrahdale and butternuts are the least vigorous of the trailing types. Japanese pumpkins have become popular because of their flavour, and production is now only slightly less than Jarrahdale.
Pumpkins are marketed from Carnarvon from late May to January and from Kununurra from late June to November. Production in summer and autumn is from Perth and the south-west. Kununurra is now the biggest growing area in Western Australia and also sends fruit to Eastern States markets.
Jarrahdale and Japanese pumpkins comprise about three-quarters of total production, with butternuts making up most of the remainder.
Pumpkins are often grown by farmers in south-western Australia as an opportunistic cash crop because labour and financial requirements are less than for most vegetables. The crop can also be harvested at one time and stored for many months. However, for these reasons, supply may exceed demand, leading to poor prices.
Pumpkins need temperatures greater than 22oC to grow and mature. They are killed by frost and need to be protected from strong winds.
Deep, well-drained loamy soils are preferred. Pumpkins will grow and yield well on heavy soils unsuitable for many other vegetables. Organic matter must be applied to sandy soils to produce good yields. The optimum pH (CaCl2) is 5.8 to 7.0. Pre-plant cultivation usually includes at least one deep cultivation to allow good root growth.