Article in English: Microwaving works best for flowers with many petals, and no hairy or sticky surface. Roses, zinnias, and marigolds are good options, although varieties with thick petals might not work out. Pick the flowers when half-open and firm, before petals start dropping. Cut the stems pretty short for this method — about 1–2 inches (2.5–5cm) Remove the container from the microwave. Cover the container, leaving the lid slightly ajar, and leave it alone for 24 hours. The desiccant (especially silica gel) can take a long time to cool to a safe temperature.  Leave dahlias, pansies, and peonies for 36 hours instead. Larger, thicker flowers such as roses and carnations may be ready in as few as 10 hours. Keep this out of reach of children and animals.

Summary in Chinese:
挑选鲜花。 让它冷却一天。