Cut the stem low, check for insects hiding in the flower, on the stem and under the leaves. Bring them indoors and place in water immediately. For miniatures, use a small container or vase and cut stem a couple inches long. Bunch up a variety of colors for an eye-appealing arrangement. Add a small sprig or two of Baby's Breath.
Zinnias are somewhat resistant to insects and disease.
If insect or disease problems occur, treat early with organic or chemical insect repellents and fungicide.