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Missouri Environment & Garden



AUTHOR

David Trinklein
University of Missouri
Division of Plant Sciences
(573) 882-9631
trinkleind@missouri.edu

Preserving Flowers

David Trinklein
University of Missouri
(573) 882-9631
trinkleind@missouri.edu

Published: July 1, 2008

“The flowers he gathered bloomed their brief bright hour, then rained their petals in a silent shower.”(Richard Rowe) Perhaps the ephemeral nature of flowers is one of the things that makes them so special. Exquisite works of nature, many flowers literally are “here today, gone tomorrow.” How great would it be if we could enjoy the flowers produced by our gardens year-around? Preserving flowers by drying them is a good way to extend their enjoyment well beyond the normal growing season. Dried flowers allow us to connect with nature throughout the year in ways that plastic or synthetic plant material cannot.

Flowers and other plant materials destined for drying should be picked close to their prime. Many species can be harvested and dried at various stages of development (e.g., bud, partially opened) for added interest in dried arrangements. Always collect more material than is needed, to allow for damage. Use only the most perfect forms. Poor shapes dry as poor shapes. Use only plants and flowers free of insect and disease damage. Damage becomes only more obvious after drying. Pick flowers when they are free of dew or rain. Place stems promptly in a container of water to prevent wilting while gathering.

There are several popular methods for drying flowers. They include air drying, pressing, the use of desiccants, microwave drying and freeze drying.

Air drying flowers

Many garden flowers, as well as wild plants, can be dried simply by tying them in together and hanging them upside down in a warm, dry place for several weeks. Flowers best suited to this treatment are the “everlastings” and a few others that do not wilt readily. Some, such as globe amaranth, can be dried in bunches on their natural stems. Others, such as strawflower, should have a wire substituted for stems before drying. Table 1 (below) lists flowers that respond well to air drying.

In addition to the garden flowers and everlastings that may be air dried, many seed heads of grasses and other plants can be hung to dry. Even a few large flowers, such as peony and hydrangea, are sometimes dried in this way. However, since they are quite large, they should be hung individually rather than in bunches.

Pressing flowers

Pressing is a drying method that involves sandwiching flowers (and foliage) between layers of an absorbent material. The latter should be clean and hold the flowers firmly during the drying process. Porous materials that allow some air movement are beneficial.

Flowers are generally placed between sheets of a non-glossy type of paper. Newspapers, old telephone directories or catalogs are suitable. Absorbent facial tissues placed on the pages aid rapid moisture absorption. Tissues should be removed and flowers or foliage replaced between fresh, dry tissues and papers at the end of the first week. After the flowers and tissues have been placed in the folded newspapers or books, stack them several layers deep. Place boards beneath and on top of the stack. Put the stack in a warm, dry place with a heavy weight on top.

Another satisfactory system suitable for pressing flowers uses a combination of cardboard, newspaper and desk-sized blotter pads. Corrugated cardboard is cut into sheets slightly larger than the sheets of folded newspaper. Flowers are positioned on one side of the opened newspaper. Then the newspaper is closed and blotter paper is placed on either side.

After all flowers have been placed between the newspapers, blotter paper and cardboard, the layers are stacked and tied or taped together. They should then be placed in a warm, well-ventilated place and weighted. If large numbers of flowers are pressed, write a date on the stacks to keep track of drying time. Special presses can be purchased or constructed for drying large quantities of materials. Table 2 lists flowers that respond well to pressing.

fig 1

Drying flowers using desiccants

At times, flowers that are air-dried become misshapen during the drying process. This is especially true with flowers that have a high moisture content or a flat, open shape. These types of flowers may be dried in their natural form by burying the flowers in one of several desiccants that remove water from the flowers more quickly than air drying while at the same time holding the flower in its natural form.

In general, the most satisfactory desiccant for drying flowers at home is silica gel. Initial cost is greater than that of mixture containing borax, but it can be used over and over for many years. Since it dries flowers quickly, more flowers can be moved in and out of the mixture during a single season than in the same quantity of a borax mixture. See Table 3 for flowers and drying time using silica gel.

Silica gel is available under a number of trade names. It is white, but some types contain blue crystals that act as an indicator of the amount of moisture that has been absorbed. When these crystals are a clear blue the material is dry. As the moisture is absorbed from the flowers, the crystals gradually turn pink. At that point it is time to dry the crystals in a warm oven before using them again.

Microwave oven drying flowers

Microwave drying takes only a few minutes and provides dried flowers that look fresher and more colorful than those obtained by other methods. Support material such as silica gel must surround and support the flowers during heating and drying. Use heat-tolerant glass or microwave containers. Do not cover the containers. Place a cup of water in the oven before starting to help prevent excessive drying.

Drying times vary from about one minute for smaller or thinner-petaled flowers up to three minutes for dense flowers with many petals to. Since ovens and flowers vary, some experimentation will be required. Microwave drying does not work well on flowers with thick petals.

After microwave treatment is complete, leave flowers in the silica gel for 12 to 24 hours to make sure they have cooled and are dried. Since microwave-dried flowers tend to absorb air moisture, spray the petals with hair spray or lacquer and store in an airtight container.

Freeze drying

Perhaps the most effective (naturalistic) method of flower preservation involves freeze drying. In this process the flowers are placed into a refrigerated chamber and the temperature is lowered to below freezing. A vacuum is then created in the chamber, causing the moisture in the flowers to sublimate, or change from solid (ice) to gaseous (water vapor) form. The water vapor is then collected in a separate chamber and the dried flowers are allowed to slowly warm to room temperature. This process takes several days, requires expensive equipment and is best left to professionals.

In summary, drying flowers is easy to do, requires little equipment and can lead to a satisfying hobby. Now is the perfect time to gather the excess from your garden and preserve it for future enjoyment.

Table 1. Flowers suitable for air drying
AcrocliniumLarkspur
Baby’s breathScarlet (and blue) sage
Bachelor’s buttonSea lavender
Bells of IrelandStatice
CockscombStrawflower
Globe amaranthYarrow (yellow varieties dry best)
Table 2. Flowers suitable for pressing
AgeratumHeather
AlyssumHydrangea
AzaleaLarkspur
Bleeding heartLily-of-the-valley
Butterfly weedMarigold
CandytuftNemesia
Celosia, cockscombPansy
ChrysanthemumPhlox
ColumbinePrimula
CornflowerQueen Anne’s lace
CosmosRose
CrocusSalvia
DaffodilStatice
DaisySweet pea
DelphiniumVerbena
GeraniumZinnia
Golden red 
Table 3. Flowers suitable for silica gel (and normal drying time)
Anemone (2-3 days)Larkspur (2)
Baby’s breath (2-3)Lily-of-the-valley (2)
Bachelor’s button (2)Marigold (3-4)
Black-eyed Susan (2)Pansy (2-3)
Canterbury bells (3-4)Peony (2-3)
Cosmos (2-3)Queen Anne’s lace (2)
Crocus (2)Rose (2-3)
Daffodil (2-3)Salvia (2-3)
Dahlia (2-3)Snapdragon (2-3)
Daylily (1)Stock (3-4)
Daisy (2)Sunflower (2)
Delphinium (2-3)Sweet pea (2)
Foxglove (3)Tulip (2)
Gladiolus (2-3)Verbena (2)
Hyacinth (4-5)Yarrow (1)
Iris (2-3)Zinnia (2-3)
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