As beautiful as flowers may be, they can't last forever--but enthusiasts would like to argue otherwise. With the proper techniques, the otherwise transient beauty of flowers can be frozen and maintained for extended periods, for aesthetic or sentimental purposes. Zinnias, in particular, are quite well-suited for this treatment, and can serve as a wonderful addition to your home's ambiance.
Cut the stems about two inches below the bloom. Zinnias are best cut after the morning dew, and best transported on a cloudy day. Flowers are purposely kept away from direct sunlight while drying, to prevent their brilliant colors from fading.
Take a shallow cardboard box, and dust the bottom of the box with a layer of silica gel. Silica gel is used to absorb moisture, and is readily available is large quantities at craft stores. Borax, also known as sodium borate, is also a popular curing agent, although it is less readily available, and slightly more toxic--handle with care and gloves.
Place the blooms, bloom-side down, in a shallow cardboard box. Coat the blooms with another layer of silica gel, until the blooms are completely covered. The stems should still be visible. In time, the silica gel will slowly remove the moisture from the zinnias, thereby preserving them for collection or framing.
Place the box into a dark closet for two weeks. Alternatively, or in the interest of time, the blooms can also be dried in a microwave for about two minutes, depending on the setting. In this case, however, the blooms should be contained in a microwave-safe glass jar, along with a cup of water (placed in the microwave simultaneously) that serves to protect your microwave.
Remove the flowers, and gently dust off the blooms with a soft brush. Some gel may have become lodged in the zinnia's crevices--you may need a needle to gently remove the final traces of the silica. If you microwaved your zinnias, you'll have to let your zinnias stand for at least ten minutes after removal, although they can be left to stand for as long as you like.
Prepare the dried zinnias for storage or presentation. Dried flowers can be attractively stored in a custom-purpose shadowbox (a framed box with a glass front). And depending on your desired presentation, florist wire can reproduce the appearance of stems.