The buds are visible, but the flowers never arrive. The lack of flower development can be due to one or several different factors, says UC master gardener Bill Pierce. Through time the trees that are providing shade for the hydrangeas might be blocking too much light and need to be thinned. While hydrangeas need protection from the hot afternoon sun, they require bright light to develop flowers. Perhaps you are pruning out the flowering wood.
Flowers develop on wood that grew the previous year.
That is why pruning these shrubs in August or September consists of removing only the wood that flowered a month or so before. Your plants may need fertilizer. Phosphorus, the second number in the fertilizer formula, is credited as being the bloom maker. I live in Loomis. I unearthed several granite boulders when I excavated to build our house.