Initially, the cucumber plants in my first baboon-proof cage only produced a few slow-growing cucumbers.  I found out that this was because the small pore of the shade cloth prevented bees from entering to pollinate.

Unlike wind-pollinated tomatoes, which have both male and female organs in the same flowers, cucumbers grow separate male and female flowers. For this reason, cucumbers require pollinators, such as bees, to pollinate them.

I overcame this challenge by hand pollinating the cucumber flowers with a small artist's paintbrush using a method similar to the method described by Becca Badgett below. I pollinated the flowers every day once the flowers started blooming for approximately three weeks.   Male flowers differ in appearance from female flowers by having shorter stems and growing in clusters of three to five. The female flower blooms singly; alone, one per stalk. 

Female flowers contain a small ovary in the centre; male flowers lack this.  The female flower will have a small fruit at the base of her stem. 

Hand pollinating method.

Flowers open in the morning, and pollen is only viable during that day. Locate the yellow pollen inside of male flowers. Pollen is sticky, so expect cucumber plant pollination to be a tedious and painstaking process. 

Remove the pollen with a small, clean artist's brush or break the flower off and carefully remove the petals. Roll the yellow pollen on the male anther onto the stigma in the centre of the female flower. One male anther can pollinate several females. This process should be repeated for adequate hand pollination of cucumber. This method requires waiting to pollinate until later flowers develop, as early flowers on young vines may produce inferior cucumbers. 

I was delighted to see small cucumbers appear and grow into delish slicing cucumbers. I ended up with a good harvest for the season.

Early blooms may be exclusively male. The practice of hand pollinating cucumbers allows vines to grow and have more productive female flowers, usually eleven days or more after buds begin.

Source: Becca Badgett, Co-author of How to Grow an Emergency Garden