Solution pH and EC Affects Vase Life of Cut Dendranthema, Dianthus, Helianthus, and Zinnia

Water quality can have a significant impact on the vase life of cut flowers.  The effects of vase solution pH and electrical conductivity (EC) on the vase life and various postharvest characteristics of Dendranthema ‘Naru Lavender’, Dianthus ‘Burgundy Sangria’, Helianthus ‘Sunbright’, and Zinnia ‘Benary Giant Scarlet’ were investigated.  Vase life of Dendranthema increased to 14.6 d in acidic solutions from 6.1 d for distilled water.  Solution uptake of cut Dendranthema was also greater in acidic solutions (94 mL) compared to distilled water (76 mL).  There was no significant difference in vase life of Dendranthema when solution EC ranged from 0.50 dS·m^-1 (21.7 d) to 4.00 dS·m^-1 (19.3 d) from NaCl; however, all solutions with NaCl resulted in a longer vase life than distilled water. For Dianthus the use of buffers to alter pH reduced vase life from 24.4 d for the non-buffered control to 19.9 d for the citrate buffered solutions, but no effect of actual pH was noted.  Additionally, increasing the EC from 0.00 to 4.00 dS·m^-1 decreased vase life by 10 d.  Cut Zinnia stems were not influenced by solution pH, but as EC increased from 0.00 to 4.00 dS·m^-1 vase life decreased from 10.6 to 6.8 d.  Helianthus vase life was not affected by EC, but decreasing pH increased vase life by 1.1 d when held in acidic solutions compared to basic solutions.  The use of commercial holding solution reduced the negative effects of high EC on salt-sensitive Dendranthema, Dianthus, and Zinnia and increased solution uptake.  For Dendranthema vase life was 24.6 d when held in preservative at an EC of 2.50 dS·m^-1, while without preservative at the same EC it was reduced to 17.4 d.  For Helianthus, solutions with preservative had a solution uptake 10 mL greater than solutions without preservative.  In general, stems with longer vase lives also had a high incidence of necrotic leaves and petals, petal wilt and bent neck.   In conclusion, each species had unique reactions to the vase solution treatments, but the general effects were consistent: high solution pH or EC or the use of buffers either had no effect or reduced vase life and the use of floral preservatives increased vase life.