Poinsettias are popular for their colorful bracts and long keeping quality under indoor conditions. However, along with the long display life comes the maintenance issue of repeated waterings that can be labor intensive. It would be useful to have a slow-release water product that could be applied postproduction when extended watering intervals are desired. CW is a soft gel formed by combining a cellulosic substrate (e.g., carboxylmethylcellulose) with a hydrated metallic salt (e.g., zinc sulfate) (Avera, 1989). When the gel is in contact with the growing medium, the water is slowly released as the microorganisms in the growing medium produce cellulolytic enzymes that break down the cellulose matrix (Avera, 1989; Nie et al., 2004). This slow release of the water has the potential to extend watering intervals. There are no peer-reviewed publications dealing with the use of CW for supplying water for containerized plants indoors. The only paper in the literature that evaluated CW for use with containerized plants used azaleas (Rhododendron indicum) held in a shaded greenhouse and CW, applied at the recommended rate to the growing medium surface, kept the plants from wilting through the 4-week evaluation period (Dellavalle, 1992).
Unlike PAM granules, CW comes fully hydrated as a result of the manufacturing process. With PAM, the amount of hydration can vary with water quality, growing medium, presence of fertilizer salts, and other factors (Bowman et al., 1990; Foster and Keever, 1990; Johnson, 1984; Lu et al., 2002; Shim and Choi, 2010; Woodhouse and Johnson, 1991). CW differs from PAM in that it does not have the potential to rehydrate. Another difference between CW and PAM are the recommendations on their use. CW is applied with limited contact with the growing medium and not mixed with it, whereas PAM is mixed thoroughly with the growing medium before planting or applied with full growing medium contact down holes made in the growing medium of pots with established plants. For CW, the contact area between the gel and the substrate, as well as the microbial populations, affect the rate of water release (Solidwater, 2011). With PAM, water release is an osmotic mechanism. The two objectives for these experiments were to see whether using CW could extend the days to wilt and intervals between waterings of potted poinsettias held under simulated home/office conditions and to see if PAM granules applied postproduction could also extend the time to wilt under the same interiorscape conditions.
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