Good thing about holistic beekeeping, you don't rely on one product only, but you do make use of a many bee products. Example: pollen. I trap pollen and it is the second valuable bee product that you can make - plus it is much more reliable than nectar. There always is pollen, but nectar is different.
Anyway, right now the blackberries are in full bloom and thus the pollen in the traps turn grey:
In the same apiary some hives do not forage on the blackberries. Instead there is a more colourful picture in the traps.
Interesting enough, that there are always some hives in the aipiary, who forage on different sources of nectar and pollen.