I've a couple of blueberry plants, one in a large pot, the other recently transferred into the ground. Both have failed dismally to live up to the promise of rich harvests. Typically they produce quite a lot of flowers, which then begin to turn into fruit. However only a very small number ever end up as ripe berries. Most wither away as if the plant decided it couldn't be bothered after all. I must admit I have fed them infrequently. Is this the likely explanation, and if so, how often should I feed them and with what type of plant food?

I think it is less about the fertilizer and more about the correct soil. Also, two different varieties are generally required for good production even when the variety claims to be self-fruitful. The varieties selected must be blooming at the same time so pollination can be successful.

Blueberries need really acidic soil, much more acidic than for the vast majority of plants. If the soil is not acidic enough, the blueberries cannot absorb the nutrients they need. So even if you were fertilizing them and all the nutrients are there in the right amounts, they still can't use them if the soil is only mildly acidic or (worse) neutral/alkaline.

They need bog-like conditions with lots of peat and a pH between 4.0 and 5.0. So first, make sure your pH is amenable. Without the correct pH, blueberries can't use many of the nutrients. Having soil which is not acidic enough is probably the #1 problem with growing blueberries.

Neither peat, nor any other 'acidic' organic material ends up creating acidic soil. Use sulfur, or mir-acid, Peat will help soil retain moisture only.. If your soil is inherently alkaline, you will need to grow blueberry in pots.

Bronzing leaves and fruit drop hint at wrong PH.

Wonderful! Thanks everyone. I shall give sulphur a whirl.