How to Lengthen the Vase Life of Dahlias

Although among the most showy of bouquet flowers, dahlias (Dahlia spp.) also can be among the most short-lived. Their stems don’t always take up water easily, and their sap can foul it. If you want your dahlia flowers to last more than a couple of days in a vase, then get them in hot water. Hardy in U.S. Department of Agriculture plant hardiness zones 8 through 10, dahlias often are grown as annuals elsewhere.

Metal bucket

Bypass pruning shears or sharp knife

Waterproof gloves

Waterproof container

Bleach

Liquid thermometer

Teakettle

Commercial bulb flower food (optional)

Measuring spoons (optional)

Sugar (optional)

Alum (optional)

1-quart container (optional)

Newspaper

Large coffee mug

Plan to pick your dahlia flowers in late afternoon or early evening rather than in the heat of the day. If that time period doesn’t work for you, then try to do it in early morning instead. Clean a metal bucket, flower vase and bypass pruning shears or sharp knife with a solution that is 1 part bleach and 9 parts water. Wear waterproof gloves while preparing and using the bleach-water solution.

Fill the metal bucket with warm water -- roughly 100 to 110 degrees Fahrenheit. Carry it with you into the garden, along with your freshly cleaned pruning shears or knife.

Harvest dahlia flowers immediately after they open fully. After cutting a flower's stem, snip off all its leaves that will be under water in your vase, and plunge the stem into the bucket of water. Re-cut the base of that stem, at a 45-degree angle, beneath the water. Repeat this process for the other dahlias you harvest.

Carry the blooms for your bouquet into your home. Put water in a teakettle, and heat the teakettle on the stove top. Fill your vase with warm water, and dissolve a packet of commercial bulb flower food in it while the teakettle water heats. If you don’t have flower food, then add 2 teaspoons of sugar, 1/2 teaspoon bleach and 1/4 teaspoon of alum to each 1 quart of water instead. That recipe is from the University of Illinois Extension website.

Wrap the heads of the dahlia flowers loosely in newspaper, leaving only the stems exposed. Pour 1 to 2 inches of the teakettle's boiling water into a large coffee mug, and immediately plunge the bases of the dahlia stems into that steaming water, holding them there for about only 30 seconds while the newspaper protects the flower heads from the heat.

Remove the dahlia flowers' stems from the boiling water, and arrange the flowers in your vase. Place the vase of flowers in a cool, dark location, such as a refrigerator, cooler or cold room, and leave it there overnight.

Choose a site for your bouquet in the morning. The site should be out of direct sunlight and away from other heat sources. Pour the old water from the vase about once every two days, clean the vase with a bleach-water solution as you did previously, refill the vase with fresh warm water and flower food, and re-cut the ends of the dahlia stems under water before returning them to the vase.

Place the bouquet in your refrigerator at night or during other times when you are away. The appliance's cool temperatures will help preserve the flowers.