Preserving Plant Materials

Drying with Desiccants
Plant materials which wilt readily must be dried in a supportive material. The two most satisfactory are a sand-borax mix and silica-gel. Others, such as kitty litter, perlite, sawdust, cornstarch and cornmeal, can be used but are not as reliable.

Borax-sand: A mixture of 2 parts borax with 1 part fine sand is an inexpensive, yet effective desiccant medium. Drying by this method takes 4-14 days, depending on the material being dried. Adding 3 tablespoons of uniodized salt to each quart of this mixture will help flowers retain their original color. The material is lightweight and faster than using only sand. Do not use borax alone, as it may cause bleaching.

Silica-gel: Silica-gel is especially effective for drying delicate flowers. It is lighter than borax-sand and is the fastest drying agent available. (A quicker drying time usually means a truer blossom color.) Drying usually takes 2-7 days. It may be purchased from florists or garden centers as well as hobby and craft shops. Silica-gel crystals are expensive but may be used indefinitely. As the crystals absorb moisture, they turn from bright blue to pinkish gray. To reuse, they must be dried by placing in a shallow pan in a warm oven (250-275o F) for several hours. A microwave oven takes only a few minutes. The crystals should return to their original blue color when dry. Store in an airtight container.

How to use desiccants. Choose containers such as boxes and cans that will allow the material to be dried without overlapping or crowding. Pour 1/2 inch of desiccant into the bottom of the container. Place the first layer of flowers on top. Flat-faced flowers such as daisies may be placed face down; all others should be arranged face up. Gently place the drying agent around and over the flowers. Be careful to retain form and keep petals in their natural position. Add desiccant until the flower heads are covered.

It is a good idea to have a test flower conveniently located in the container to permit a check on the dryness without disturbing the entire contents. Cover the container and do not disturb.
Drying is complete when flowers are crisp and dry but not brittle. The thickest parts are slowest to dry. If only the petals are completely dry, the flower may be removed and air dried to complete the process.

To remove dried flowers, gently pour off desiccant. Wisk away any remaining drying medium with a soft brush. After drying, white or clear glue may be placed at the base of some flower petals to prevent shattering.

Microwave Oven Drying
Microwave drying takes only a few minutes and provides material that looks fresher and more colorful than that obtained by other methods. Use a desiccant such as silica-gel to support the flowers in a glass or special microwave container. Do not cover the container. Always place a cup of water in the oven before starting to prevent excessive drying.
Drying times vary (see Table 1). A standing period following drying is necessary to allow cooling and complete drying.

Table 1. Microwave Oven Flower Drying Times
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Heating Standing
Flower Time Time
(minutes) (hours)
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African Daisy 3 10
Aster 2-1/2 10
Calendula 2-1/2 10
Carnations 1 10
Clematis 3 10
Chrysanthemum 3 10
Daffodil 2-1/2 10
Dahlia 5 to 7 36
Delphinium (Larkspur) 4 to 5 10
Dianthus 3 10
Dogwood 2-1/2 24
Marigold 3 10
Orchid 1-1/2 to 2-1/2 24
Pansy 2-1/2 to 3 24
Peony 3 to 4 36
Poppy 2-1/2 to 3 24
Rose 1-1/2 10
Salvia 3 24
Scilla 2-1/2 10
Tithonia (Mexican Sunflower) 5 to 6 10
Tulip 3 24
Violet and Viola 2-1/2 to 3 10
Zinnia 4 to 5 10
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Michael N. Dana and B. Rosie Lerner. 2008. Preserving Plant Materials. Department of

Horticulture Purdue University Cooperative Extension Service • West Lafayette, IN