Buying someone flowers is always a delightful gift, but usually ends up being shorter-lived than we’d like. There are some things you can do to prolong the life of cut flowers.
The first thing to do is to cut the bottom off of the stems to make fresh openings in the flower’s vasculature because the original wound site will callous and seal off over time, causing the flowers to dry out more quickly. But here’s the key: you need to cut the stems under water. If you cut the stems in the open air the freshly exposed veins will initially take up air, creating an air embolism. This air embolism interferes with the flower’s ability to transfer water through its veins.
Also, if you make an angled cut, you’ll open up more of the stem to pull in as much water as possible
Second, put the freshly cut flowers in a container full of water that is slightly acidic. Acids prevent callous formation. This way the wound site of the cut flowers will not callous over and water will be free to flow up the stems to the flowers. You can make your vase water acidic by adding vinegar or lemon juice. Less than a tenth of your water volume should be the acid: a 10 ounce (29.6 milliliter) glass, for example, should have 9 ounces of water and less than 1 ounce of vinegar or lemon juice. For regions with hard water (usually arid/desert climate areas), you may need to use more acid. Just be careful not to use too much… er on the side of caution and add more if you think it needs it.
This is especially important if you have a flower arrangement with daisies in it, or any member of the asteraceae family. Flowers from this family tend to exude a gluey substance that will gum up the stems of the other flowers. Lemon juice helps to prevent this from happening.
Third, put a little sugar in the water. Just like you and me, plants need carbohydrates. Since the flowers are cut they can’t make their own food as well as they normally would, so a little sugar helps keep them fed. You don’t need very much; a few of pinches of sugar to a 10 ounce glass.
Fourth, you can add a biocide. This may seem odd but we need to control any bacteria or fungi that may try to feed on the flowers or the sugar we added to the water for the flowers. Our goal here is to add just enough biocide to kill germs but not enough to harm our flowers; it’s kind of a balancing act. A good household biocide would be bleach or rubbing alcohol. You may have to experiment with this one; If your flower water starts to become murky (a sign of growing bacteria or fungi) add more biocide. A good start is a few drops of biocide to a 10-ounce glass.
The bouquet at the left was a gift to my wife. Using these techniques, about 2/3 of the flowers still looked quite nice at 3 weeks.