I noticed that DG's word of the week is rosa-sinensis. I read something in DG's definition that is rarely stated or known. The petals are edible. As a collector and part-time hybridizer of Hibiscus rosa-sinensis for many years this is something I practiced all the time. They are a good source of vitamin C. I usually serve them up in a tossed salad. Better yet, if you're entertaining or bringing the salad to a dinner party, line the bowl with petals finishing with the outer edge of petals forming a halo around the edge of the bowl. Makes a great presentation and this simple salad will be the talk of the dinner. The dilemma is that the blooms that are left on the plant will not remain crisp by an evening dinner.
The trick for making the bloom wait until later in the day to open is to pick the buds in the morning before they open. Wrap them in a moist paper towel and put in the crisper of the refrigerator. About 4 hours before they are to be used take them out and set the buds upright in a warm location. A way to do this is by using conical drink or snowcone cups with the tip cut out just large enough to hold the bud upright. Sometimes they may need a little gentle help in opening.
Disclaimer: The plants must not be treated with any pesticides, miticides or any other chemicals not labeled for food source plants. Read the labels before proceeding.
Several Hibiscus species and relatives have edible parts, which may be good in salads, teas & other drinks, and cooked vegetables. However some precaution should be taken, especially if taking medication.