[AliP]

I have grown cucumbers before (indoors) without issue but this year, while the volume of crop is good, the majority of cucumbers are so bitter they are inedible.  Any ideas why this has happened, and if there are any varieties less prone to bitterness?

[Kleftiwallah]

Good afternoon AliP, 

I believe (but don't quote me on this) the cucmbers have been fertilised.  I remember being told long long ago to remove all male flowers from the plant, now 'they' have bred "All female" plants.

Cheers,   Tony.

[JayG]

Which variety? - all-female cukes sometimes produce male flowers which can result in the female flowers producing bitter fruits.

That aside, being cukes, almost anything else is a possible cause - over/under/inconsistent watering, too hot/cold, nutrient shortage (they can need more pampering than any other crop but are pretty rewarding when you manage to get it right!)