Drying Flowers in a Microwave

A microwave can be used to speed up the flower drying process. However, this method doesn’t work for all flowers. It’s best used for flowers with many petals and deep forms such as marigolds, roses, carnations, and zinnias. Flowers with thin, delicate petals or those with hairy or sticky surfaces are not as successful. Be sure to pick flowers that are about half-open and firm. Flowers that are in full bloom may be appealing to the eye, but they lose their petals easily. Also, keep colors in mind when selecting blooms. Yellow flowers retain their color well, but white ones may become dull gray-brown after drying. Dark red flowers and others with deep hues may become even darker during drying.

Harvest the flowers late in the afternoon when they are at a point of low water content. If the stems are cut off the flowers and only the heads are used, you should pre-wire them. This is particularly useful for roses, zinnias, and lilies to name a few. Once the flowers are dry, it is next to impossible to get them wired without shattering them.

After carefully selecting what you want to dry, the next step is to fill a glass, cardboard box, or other microwave-safe container to a depth of 1 to 2 inches with a supportive material such as silica gel. Silica gel, fine, white, sand-like material, is available at florist and craft shops as well as a number of other stores. It acts as a desiccant and is reusable as long as it is properly dried between uses. You can also use kitty litter or equal parts of borax and cornmeal instead of the silica gel. If you are attempting to dry flowers with very delicate petals, silica gel is preferred.
Place flowers, right side up, in the container. Space them so they do not touch each other or the sides of the container. A general guide is to allow at least 3/4 of an inch between flowers. Next, carefully sift silica gel over the tops of the flowers until they are covered. Work it around the blossoms so all flower surfaces are covered. You may need to tap the container to make sure the silica gel has settled properly. You can also use a toothpick to separate petals and help ensure they retain their original shape.

Place the silica gel-covered flowers in the microwave. Set the oven timer for the period listed in the table below for the particular flower you are drying. Note that some flowers only need 1 to 3 minutes of heating time while others require 5 to 8 minutes. Use a full-power cooking setting. The times given in the chart are only guidelines. The actual time may vary due to the type of oven and the amount of moisture in the flowers. If your oven does not have a turntable, you may want to rotate the containerevery 1/2 to 1 minute.

To test for dryness, use a toothpick to gently move away enough of the hot silica sand to see the petals. If they do not appear to be completely dry, place them back in the microwave oven and heat for one minute, making sure the flowers are completely recovered with the silica sand. It doesn’t take long; flowers can be over-cooked and become extremely brittle if heated too long. Experiment before you do large amounts.

After heating, remove the container from the microwave oven and leave the flowers in the silica sand overnight to allow the silica crystals to cool completely. The minimum standing times for the various flowers are given in the table below. When the silica sand has cooled, tip the container gently so the crystals flow off the flowers slowly. As the blooms become uncovered, carefully slide two fingers under each and lift out. Shake the flowers gently and use a fine, soft brush to remove any remaining crystals. If you don’t plan to use the flowers immediately, store them in a plastic bag or box of shredded newspaper to help them hold their shape.
If you used silica gel as the drying agent, you can save it and re-use it but it must be reactivated. You can do this by spreading the silica gel on a cookie sheet and heating it in an oven at 250 –300o for 2 to 3 hours. Silica gel should be reactivated when the color indicator begins to turn pink. As it is reactivated, the color indicator will turn blue.

Recommended Drying and Standing Times
for Flowers Dried in Microwave

Drying Time Standing time
(in minutes) (in hours)
Anemone (Anemone sp.) 2 1/2 to 3 12
Aster (Aster sp.) 2 1/2 10
Calendula (Calendula officinalis) 2 1/2 10
Carnation (Dianthus caryophyllus) 1 10
Chrysanthemum (Chrysanthemum sp.) 3 10
Daffodil (Narcissus sp.) 2 1/2 10
Dahlia (Dahlia hybrids) 5 to 7 36
Delphinium (Delphinium elatum) 4 to 5 10
Marigold (Tagetes sp.) 2 1/2 to 3 10
Pansy (Viola x wittrockiana) 2 1/2 to 3 36
Peony (Paeonia hybrids) 3 to 4 36
Poppy (Papaver orientale) 2 1/2 to 3 24
Rose (Rosa sp.) 1 1/2 to 2 10
Salvia (Salvia sp.) 3 24
Tulip (Tulipa sp.) 3 24
Zinnia (Zinnia sp.) 4 to 5 10

James C. Schmidt, HorticulturistUniversity of Illinois