Rehydrating and Pulsing
This is done to regain the water content of the cut stem; it is particularly important where flowers have been out of water for some time. If the cut flowers are water stressed, then they must be completely rehydrated before being put in pulsing or preservative solutions.
Rehydrating solutions always contain an acidifying agent such as citric acid, 8-Hydroxy quinolene citrate (or sulphate) or aluminium sulphate (Alum.). Adjust the pH of the solution to pH 3.5 - test this with litmus paper or swimming pool pH test strips.
A biocide can also be added along with an anionic wetting agent such as Agral (r) at very low concentrations (0.01 - 0.1%). Current research work is demonstrating that wetting agents are suitable for woody-stemmed cut flowers, including roses, particularly those that have been out of water for sometime. Roses must be rehydrated before putting in arrangements.
Sugar is not used in rehydrating solutions as it makes the water more viscous so it slows down water movement up the stems.
Make up rehydrating solutions each day if possible. Discard them as soon as they are slightly cloudy. A basic recipe is 2.5g/10L citric acid plus a few drops of bleach.
As the name implies, these solutions are used to give the flowers a pulse of energy (sugar) and in some cases other postharvest treatments such as S.T.S. loading or plant hormones to prevent leaf yellowing.
In pulsing solution, the concentration of sugar can be up to 20% (200 g/L) as it is designed to give the flower an extra boost of energy to help it to withstand transport and develop properly and have a better vase life when it reaches its final destination. This is most useful for bud cut flowers such as gladioli and carnations.
In the 'Recommendations for Specific Crops' section treatments are given for each crop. Often the rate or concentration of the pulsing solution varies according to the time of treatment. Choose the treatment time that suits your routine. In general, it is best to choose the longer treatment time as there is a little room for error - the short treatment times are more exacting so it is easy to either under or over-dose flowers.
A ten second pulse of silver nitrate has also been found to have a beneficial effect basically as a germicide on chrysanthemums and gerberas. After dipping in solution, the stems are rinsed in clean water and placed in preservative solution. The part of the stem treated will be stained brown.
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