The simple answer to this question is to tell you that you should cut the flowers whenever you feel you want to bring them inside to enjoy! Home gardeners likely will follow this advice. It works fine. You can admire them in the garden for a while, then bring them inside when the flowers are fully expanded to enjoy even more.
However, the answer is never so simple when you ask SunflowerSelections.com. There are several factors to consider. First, almost all of the ornamental sunflowers at SunflowerSelections.com are pollen-free. That means that we have bred them to not produce pollen. This is an entirely naturally occurring trait that was discovered decades ago when sunflower plant breeders were crossing wild sunflower species with cultivated sunflower varieties much the same way bees would cross flowers in a field. However, careful observation showed that some plants from seeds of these crosses did not produce pollen when they flowered the next generations. This discovery became the backbone of technology upon which the hybrid sunflower industry rests today allowing the stable production of oil and snack sunflowers on millions of farm acres around the world.
Researchers at SunflowerSelections.com saw more opportunity. Not only did the discovery of this trait allow us to make new hybrid color combinations in predictable ways, but it meant that we could offer pollen-free sunflowers to the home and professional sunflower grower. This eliminated pollen drop on tables and furniture in the home and meant even people allergic to sunflower pollen could now enjoy a bouquet of cut sunflowers.
You might wonder how the sunflowers feel about this? Well, they still produce nectar deep down in the florets and the bees still visit those flowers to collect that nectar.
And the flower will even make seeds if the bees arrive with pollen on their abdomens and legs from other pollen shedding plants in the neighborhood.
Now, finally we can answer the question about when to cut sunflower. Professional cut sunflower growers want to cut flowers as soon as it is possible so that they can achieve the longest possible vase life in order to have time to transport, sell, and assure that their customers enjoy the open flowers in an arrangement or bouquet. Furthermore, cutting the flower at this early stage eliminates any chance that bees or other insects may have started to pollinate the sunflower florets. Such pollination would result in fertilization and the beginning of seed development which would hasten flower senescence and cause early petal drop.
Sunflower can be cut when you first see the ray petals begin to push out of the flower disk. Ideally, the petals are at right angle (90 degrees) to the disk of the flower.
ProCut Orange at perfect flowering stage for cutting.
We recommend that the plants not be stressed at cutting time. And we like to cut in the early morning or evening, avoiding the heat of the day. The stems should be placed immediately in buckets of ambient temperature or better, lukewarm water and kept out of direct sun. Cut plenty of stem length so you can trim when you arrange the flowers.