I posted this response to zinnias and preservative solution on April 22:

The only flower we have learned that does not like hydrating solution or preservatives is zinnia. Zinnias don't like sugar. They actually do best in dionized distilled water. The University of North Carolina has done some pretty indepth research on this particular flower. Zinnias are sensitive to boron, which some cities have in their tap water. As far as handing out the preservative packets, customers do appreciate them. We give packets of bulb preservative for bouquets with lilies, glads and dahlias (which are actually tubers). We give the regular preservative for all other bouquets. For, the growers bunches of zinnias we always recommend the distilled water.

As far as the single stem sunflowers such as Sunbright, Pro Cut, Sunny, etc., we don't use preservatives. These sunflowers last so long that we have found it really isn't necessary. We had a bucket left from one of our markets. We set it on a bench in front of our barn in direct sunlight. We never changed the water or did anything to those sunflowers; and, they lasted a good 10 days.