Success With Pumpkin In The Subtropics

Pumpkin, Cucurbita moschata 'Jap' aka Japanese or Kabocha

Pumpkin, Cucurbita moschata ‘Jap’ aka Japanese or Kabocha

Question: When do I sow pumpkin? I read in gardening magazines pumpkin can be sown from spring to autumn in the subtropics. But advice on seed packets (and some magazines) suggest that pumpkin should only be sown from spring to summer. I have a garden at Camp Mountain 4520 where we do not get frost, please help.

Subtropical springs are hot and dry, conditions which stimulate pumpkins (Cucurbita moschata) to almost exclusively produce male flowers.

I also find that European honeybees aren’t very effective pumpkin pollinators, so each morning, while the pollen is fresh and viable, I hand pollinate any female flowers.

Traditional cultivars, like ‘Beaudesert Blue’ and ‘Hartley’s Ironbark‘, require 125 – 150 growing days. They fruit best after midsummer, responding to decreasing day length (and increasingly long nights).

Exhibition pumpkins, like ‘Atlantic Giant’ require 150 days or more, but modern cultivars, like ‘Butternut’ require just 80 – 85 days to crop.

Pumpkin should be harvested before the end of autumn, so calculate your sowing date by working backwards according to the time the cultivar you grow takes to fruit.

Sprinkle half a handful of dolomite per square metre and rake this into the surface a fortnight to three weeks before sowing. The calcium eliminates Blossom End Rot, caused by calcium deficiency.

Plant pumpkin into mounds of well dug, compost rich soil about 15 – 20cm high, or sow three seeds per mound and remove the two weakest seedlings, retaining the strongest. Pumpkins need 6 – 8 hours full sunshine to develop fast, and too much shade encourages mildew. Remove the end of the growing point once a pumpkin fills a garden bed. Water plants in the morning and avoid wetting the foliage, both help reduce the risk of mildew.

Pumpkin tend to develop mildew once they begin to flower, and spraying foliage weekly with a solution of one part pasteurised cow’s milk per five parts water effectively retards the development of this fungus.

‘Jap’ Pumpkin, Cucurbita moschata ‘Jap’ aka ‘Japanese’ or ‘Kabocha’, is an old-fashioned pumpkin cultivar suited to hot, humid conditions, well worth trying in the subtropics.

Jerry Coleby-Williams

29th October 2014


Allen K: “Jap pumpkin is so productive. 20+ pumpkins in a season. And if strong and healthy it can do that 2 years in row if no frost. Just cut back but keep some well rooted sections”.