Grape vines, at least those used for wine, are self pollinating. They don't need bees, or birds or any outside help to flower. The flower simply opens up and drops it's pollen on to the seed below. The flowers are tiny, less than 1mm across. The pollinated flowers become the individual grapes in each cluster.
So the success of flowering is very big in determining how big your crop will be each year. The best thing you can do as a farmer to help is -- Nothing. The flowers are so small that it's very easy for the pollen to 'miss' and you end up with a grape pod that won't turn into a grape. These are called 'shot berries'. If you get a lot of shot berries this is called 'shatter'. In that case you end up with a cluster with just a few grapes on it.
So when flowering starts, you want to stop doing anything to the plant. No trimming, no spraying, no shaking the plant in any way. You also hope the wind stays calm, as high wind will cause the pollen to miss, and leads to shatter. Rain or hail is the very worst, it will release the pollen and wash it away.
We've just started to see flowering. So far the weather has been very good, and I've stayed out of the vineyard. I'll have to cut my work back now to things that won't disturb the plants. When flowering is over, we call this 'set'. That means the clusters have set their good berries and the grapes will mature through the summer. Once we have set, I'll return to the vineyards.