Achillea

34 DRYING AND PRESERVING
freeze-drying equipment and polymer chemistry have resulted in more and more
flowers being freeze-dried, particularly stems and flowers with high water content.
Small equipment designed for the florist industry is available, as well as
high-volume dryers for wholesalers and wholesale growers. Freeze-drying provides
flowers with a natural shape and color and extended longevity. Freezedrying
is highly technical and requires a significant capital investment; however,
it creates a marvelous product and is a viable method for delicate flowers.
Silica Gel
For many dried products, the water in the plant is transferred to a desiccant,
such as silica gel. Plants are completely embedded in the gel and remain there
until all the water has been removed. The main benefits of silica gel are excellent
retention of color and shape. Useful flowers to treat with gel are those with
high moisture content and little fiber, such as zinnias and sunflowers. Stems
seldom dry well with silica gel, and flowers dried by this method are cut with
very little stem remaining. Silica gel can be reactivated after use by heating in an
oven at 250–300F (120–150C) for 2–3 hours. Drying time will vary with the product
but is usually accomplished in 1–3 days (Koch 1995).
Dying Flowers
Many stems and flowers are colored for the marketplace, and the systemic watersoluble
dyes developed for the floral industry will provide almost any color
desired. Choice of container, solution temperature, dye concentration and handling,
wetting agents, the necessity of avoiding contamination—all are considerations
when using dyes. We recommend reading Mark Koch’s product sheet
on dying fresh flowers (Koch 1999) for more detailed information.
Reading
Koch, M. 1995. Drying flowers and foliage with silica gel. Robert Koch Industries
Tech. Bul. 460:1–8.
———. 1996a. Air drying flowers, foliage and ornamental plant materials. Robert
Koch Industries Tech. Bul. 430:1–15.
———. 1996b. Overview of current technology for drying and preserving flowers
and foliage. Robert Koch Industries Product Sheet.
———. 1999. Systemically dying fresh cut flowers and foliage with absorption
(systemic) floral dyes before air drying. Robert Koch Industries Product Sheet
102:1–4.
Many thanks to Mark Koch and Shelley McGeathy for reviewing this section.