Flower growers and florists do everything they can to get flowers to you in the best possible condition. Once you buy them it's your turn to follow the simple flower care rules that will make your flowers last as long as possible.
Drive straight home, don't stop for a long lunch and leave your flowers in the hot car - go straight home! Place your flowers on the floor of the car or anywhere out of the sun. If it's hot put the air conditioning on. Cut flowers are the most perishable horticultural product there is and it only takes half an hour or so out of water in hot conditions to cause irreparable damage.
Select the vase you wish to use and make sure it is clean. If it isn't scrub it out in the sink with a little detergent, or even better, a little bleach in water. Now fill the vase with COLD water, and add a sachet of flower preservative. If you haven't got a sachet, see the Why Use a Flower Preservative below for a recipe.
If you have a pre-made arrangement, take it out of the wrapping paper, and roll the rubber band or ties away from the stem ends. Strip any leaves off the stems that would be underwater. If you have purchased a bunch, or want to make your own arrangement, cut the rubber bands or ties, and strip every leaf from the lower half of each stem.
Cut 1-2 cm off each stem end, then place your flowers in water IMMEDIATELY.
Put your flowers in a cool position. Don't place the vase in direct sunlight, or near a heater or in a warm draught.
Make sure you top up the vase water with fresh water + preservative every day. Make a complete change of water every 3 days or so.
The simple answer to this question is that flower preservatives are designed to make your flowers last as long as possible. Most preservatives have three main ingredients that help achieve this:
Cut flowers need to take up clean water to stop them wilting. Germicides keep the vase water clean by killing bacteria, fungi and other micro-organisms that always proliferate in vases of cut flowers. These micro-organisms are on all flower stems, the vase surface and even in tap water. They feed on sugar, which is contained in the sap that leaks out of the cut flower stem ends. Happy bugs also multiply and can very quickly block the cut stem ends. Stick a bandaid over our mouth and try to suck up water and you'll know how the flower feels in dirty water! Common germicides used in preservatives are chlorine or bromine.
Flowers need sugar to open and keep those colourful petals bright. Sugar is also needed to keep fragrant flowers smelling so good. When they are on the plant this sugar comes from the leaves, where it is made during photosynthesis. Once you cut a flower off the plant and place it inside where it is too dark for photosynthesis to occur, that sugar is gone, and the flower dies. The sugar in a preservative is taken up through the cut stem end and feeds the flowers and buds, keeping them alive. Because micro-organisms thrive on sugar, however, don't ever add sugar without a germicide as this will cause a bacterial soup in the vase water before you can blink.
Cut flowers take up far more water if the water is slightly acid in nature. A pH of 3.5 is ideal. So, many preservatives contain a gentle acid, like citric acid, that will slightly acidify the water. Vinegar (acetic acid) will also work fine. Incidentally it's not entirely certain why cut flowers take up more water when it's slightly acidic.
It's easier to use a sachet of commercial preservative, but if you don't have one:
To 1 litre of water add:
1 teaspoon of bleach
2 teaspoons (10 g) of sugar
1 teaspoon (5 ml) of vinegar
3 pinches (0.3g) of citric acid.