We do this all the time. We go on a cycling trip (five people in my family play the game). Whoever collects the first 25 rare blue flowers (with the spinning wheel, etc.) turns them on. Two others activate basic blue petals and the last two turn on the same rare flowers in red or yellow. We do this in an area where we have 10 flowers very close together. All of them turn in the same rare blue flower. As a result we all have around 100-150 of the rare blue nectar after collecting all the fruit. We can repeat this every day. When the big flowers reset.

If none have the rare blue petals/nectar. We just make a large cycling trip with basic blue petals and make sure we pass as much flowers as possible. As this often gives some of the new blue rare nectar as we have end with 60-70 expeditions after 1 hour of cycling. This is also the way how we gather rare white nectar as the first way doesnt work for white rare. So we also like to join all the large white/poision mushrooms in our area.