With Halloween edging closer, August is a pivotal month for pumpkin growers. Your vines may still be producing plenty of leafy growth, but now is the time to redirect the plant's energy into developing the pumpkins already on the vine, helping them grow bigger, ripen properly and reach their full potential before autumn.
Garden designer Diarmuid Gavin shares the essential jobs to tackle this month to protect developing pumpkins, encourage healthy growth and maximise your Halloween harvest.
1. Stop new growth
In August, the priority should be supporting the current pumpkins as they ripen, rather than encouraging further plant growth.
'It’s all about directing the plant’s energy into producing fewer but better quality fruits,’ says Diarmuid, who is an ambassador for Hampton Greenhouses.
Once your plant has enough pumpkins forming, 'pinch out the growing tips of the main vines,’ he advises.
This allows the plant to strengthen the fruit that has already formed, rather than pushing out new stems.
Diarmuid also recommends removing any late female flowers that are unlikely to mature before Halloween, as they can divert valuable energy away from pumpkins that have a realistic chance of ripening.
Tip: You can tell male and female pumpkin flowers apart by looking inside – female flowers have a sticky multi-lobed centre, while male flowers have a single dusty pollen-covered stamen.
2. Prioritise the best fruit
If you're hoping to grow bigger pumpkins, August is also the time to thin your crop. ‘Leave just two or three fruits on each vigorous plant,’ advises Diarmuid, as producing fewer pumpkins allows the plant to put more energy into growing larger, healthier fruit.
Consistent watering is just as important, especially during dry spells. Rather than watering little and often, give plants a deep soak when they need it. ‘Pumpkins have extensive root systems and benefit from a thorough soak,’ explains Diarmuid.
3. Use the right feed
To support strong fruit development, feed your pumpkins once a week with a high-potash fertiliser. Diarmuid recommends using a tomato feed, which provides the nutrients needed to help pumpkins swell and ripen before Halloween.
4. Protect the harvest
To ensure your pumpkins make it to Halloween, Diarmuid advises placing mulch around the plants with compost or well rotted organic matter to conserve moisture, suppress weeds and keep the root zone cooler during hot weather.
As your pumpkins continue to grow, it's important to keep them protected from rot and pests. Gently adjust the vines if needed to give developing fruit enough space, then lift each pumpkin off damp soil by placing it on straw, a wooden board or a tile. This helps improve airflow while reducing the risk of rot and slug damage.
Once pumpkins begin to turn orange, avoid moving them unless absolutely necessary. Disturbing the fruit at this stage can damage the stem, shortening its storage life and increasing the likelihood of rot after harvesting.
5. Improve greenhouse ventilation
Growing pumpkins in a greenhouse? Make sure to keep doors and vents open on warm days. Good airflow helps reduce humidity, lowering the risk of fungal diseases, while also creating the conditions pumpkins need to ripen successfully before Halloween.
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