When Courgette, Squash, Pumpkins and Cucumbers start to flower, they normally produce male only flowers for a week or so…
The male flowers, which you will recognise as there is no fruit at the base of the flower, just a stem as pictured here, appear first to start attracting bees. Then, once the bees and other pollinators have had time to become regulars, the female flowers start to emerge (you’ll see that the female flowers have small fruits attached at the base). In theory, the plant then stands a much higher chance of successful pollination because of the presence of all the bees and the male flowers, and then they can really get growing producing lots of courgettes and squashes for you to harvest.
There’s usually a wait of around 10 days after the male flowers emerge before you start to see females. However, if the conditions are unfavourable – cold, damp or strong winds, for example – the female flowers may not come out until a little longer. If you suspect this might be why your plants aren’t producing female flowers, do what you can to improve conditions – lay a sheet of horticultural fleece over the plants, make sure they get plenty of water and think about mulching them too.
Up until very recently in the UK, the summer has been cool, and the low temperatures may have discouraged plants from putting out female flowers. Hopefully with this heatwave, any slow plants will quickly catch up now.