This has not been a good year for pumpkins, many of whom have had a celibate summer. The last few weeks have been full of gardeners demanding: "Why haven't my pumpkins, passionfruit, apricots, cucumbers, and even zucchini set fruit?"
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The answer is simple: no sex. Humans need to mate just once to produce a baby. Pumpkins need about 10-12 visits from a pollinating creature to transfer the up to 2000 pollen grains per stigma needed for full fruit set.
It's actually a miracle anyone gets pumpkins at all.
Bees are in short supply just now. Colonies vanished in the drought, fires and floods, and from Varroa mites and European wasps. Bees also don't buzz out much in the rain. Few humans do much baby making in the rain, either. That's why we invented roofs and weekend getaways with fireplaces. Rain also washes away the pollen juveniles carry on their fuzzy legs. Only young bees collect pollen. It rubs off as they hunt in the flower for nectar.
The first few flowers on a vine will be male. You can tell male from female flowers without embarrassment- female pumpkin flowers have a small bulb at their base which may- possibly- turn into a pumpkin. Female flowers are fussy. They only live a few hours after blooming, leaving little time for pollination. You'll find out if the joyful union has occurred days later when the female flower falls off. If a tiny 'ball' is left, you might get fruit. No pollination means the small ball will shrivel and fall off.
Pumpkins only bloom in the right conditions, depending on the variety. Some like it hot. Others go for temperate. Even a pollinated baby pumpkin may shrivel in hot, humid, or dry weather, or rot if a rat or wombat has gnawed their skin. Very hot days and warm nights also stress vines so much they discard their fruit. Human pumpkin pollinators need to shake a male flower over a female till all the pollen seems to have dropped off. You may also try a small paintbrush to transfer all the sticky yellow grains to the stigmas - the comparatively long 'threads' in the flower that have no pollen. This is easier with large pumpkins than small cucumber flowers, and very easy with passionfruit flowers, as they obligingly open fully, making access easy.
It's an early morning job, as female flowers usually close up somewhere between early afternoon and evening. Do not trying pollination before a storm. The pollen will wash off or you may be soggy or hit by lightning, and not so keen on gardening any more. Pumpkins also love tucker, which is why feral vines growing out of the compost heap do so brilliantly.
Many a male pumpkin grower has pointed Percy at the pumpkin vine and congratulated himself on a wildly flourishing bush. But they'll get more leaves than fruit from such a high nitrogen diet. Once a pumpkin vine begins to flower, feed it with compost or a good balanced plant food designed for veg. Regular watering is essential, but uneven watering triggers mildew. Try to water the roots, not the leaves or pumpkins.
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Baby pumpkins fall off, or rot, with too much shade. Train the vine up a trellis away from the humidity from the grass. Never mow your pumpkin vine. Pumpkins need all the tucker photosynthesis will give them.
Trial at least six varieties of pumpkin for two or three years to see what grows best in your garden.
Pick when the stem begins to dry off. Frost damage will lead to rots. Harden pumpkin skins your crop on a hot roof or tiled patio, on their sides so dew doesn't collect in the depression by them stem. Store in a dry spot on their sides, and inspect often. A rotting pumpkin makes your house smell like a rubbish bin for weeks. And if you still have no fruit, it's not too late to try hand pollination.
This week I am:
- Picking red finger limes, with hundreds of crinkly bright pink blooms among the tiny leaves.
- Seeing the garden season change with 1,000 giant golden ginger lilies.
- Reminding myself that we still haven't eaten last year's frozen tomato passata, so there is no point boiling down another pot full.
- Discovering that green basil leaves are more tender and less prone to charring on a pizza that the purple ones.
- Waking up at 2am as mum and baby possum quarrel about who gets the fruit on the passionfruit vine out the bedroom window.
- Grateful for the thick shade of the passionfruit, grape and kiwi fruit vines, with at least six layers of leaves insulating our windows from the heat.
Friends of the Australian National Botanic Gardens Growing Friends Autumn 2024 Native Plant Sale is on Saturday, 2 March 2024 from 9.00 until 11.30am (unless sold out earlier). Banksia Centre Car Park, with 1400 plants at only $6 a pot. Sales are by card only. Plants are all sourced from within the gardens.
Jackie French
Jackie French is an Australian author, historian, ecologist and honourary wombat (part time), 2014-2015 Australian Children' Laureate and 2015 Senior Australian of the Year. She also writes a gardening column for The Canberra Times.
Jackie French is an Australian author, historian, ecologist and honourary wombat (part time), 2014-2015 Australian Children' Laureate and 2015 Senior Australian of the Year. She also writes a gardening column for The Canberra Times.
