I don't think their sap, which is clearer and doesn't flow as much as daffs' sap does, is harmful to other flowers. Tulips do benefit from being wrapped so their stems are straight, then conditioning in water or preservative for 12 hours or so, wrapped, before being unwrapped and arranged. If that isn't done, the stems tend to bend way over. Tulips combine with other flowers nicely. I haven't combined daffs with anything else; early in the season when they're in bloom here, nothing else is. I haven't sold them, either, because the market I used to go to starts after the last of the daffs are done. Tulips were a big hit, but I had to grow only the late-blooming kinds, because, like the daffs, the others were done before our market started.

As for what to put in the water, there are several powdered (and maybe some liquid) mixtures, and some home-made solutions, that you can put in the water to increase vase life. Which of those you use, if any, is up to you. Powders are easy and fast but more expensive than home-mades. If you're going to be selling your flowers, it's nice to give the customers a packet of Floralife or something similar with their bouquets. I have a home-made formula I always used for harvesting, conditioning, and display, but I gave my customers a packet of Floralife Crystal Clear. I'm not selling flowers any more and find that I use my home-made formula if I'm going to be cutting and arranging multiple large vases, but use the packets if I'm only cutting for one vase. The powdered kinds are available in buckets as well as packets, for big users. My formula has bleach; the powdered things usually have a different biocide. If you're going to sell flowers, it might be worth your while to experiment with what you use. What is in your water can make a difference from one solution to another. Also, there are some flowers that don't like preservatives and are better off in plain water. Zinnias are like that. Some say sunflowers, lilies, and glads are also, but that hasn't been my experience at all.

Jeanne

Jeanne,
Thanks for your help. I haven't been on Gardenweb much this past week, as school started back up and I've been super-busy. I have been putting a packet of CrystalClear in each vase I make, giving a packet away only if it's a BIG expensive bouquet. Most of my bouquets are smaller $5 kinds.
The tulip info re: wrapping the stems was very helpful! :0) Phyl