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Extension > Garden > Yard and Garden > Flowers > Keeping cut flowers and flowering plants

Keeping cut flowers and flowering plants

Mary H. Meyer, Extension Horticulturist
Department of Horticultural Science

Copyright © 2013 Regents of the University of Minnesota. All rights reserved.

Cut Flowers

Whether cut flowers are grown in a home garden or in a greenhouse by commercial experts, their care is a science.

To keep cut flowers beautiful longer; remember that they have been removed from their source of water, the root system, and will wilt quickly if not placed in water. Cut stems should be placed in water immediately, as air will rapidly move into the water-conducting tissues and plug the cells. This is why the cut flower that has been out of water more than a few minutes should have a small portion of the lower stem cut off so that water will move up freely when it is returned to water. Cuts can be made under-water to assure no air enters the stem.

A cut flower also has been removed from a major source of food—the leaves on the plant to which it was attached. Although the leaves on the flowering stem make food, once indoors they are in a reduced light situation and this limits available carbohydrates.

Use a Preservative

Commercial preservatives will increase the life of cut flowers and should always be used. (Adding aspirin, wine, or pennies to cut flowers WILL NOT help to keep them fresh longer. Do not attempt a home brew concoction.) A floral preservative is a complex mixture of sucrose (sugar); acidifier, an inhibitor of microorganisms; and a respiratory inhibitor. Sucrose serves as a source of energy to make up for the loss of the functioning leaves and insures continued development and longevity of the flower.

An acidifier makes the pH of the water more near the acid pH of the cell sap. Most water supplies are alkaline and can reduce the life of cut flowers. The acidifier also stabilizes the pigment and the color of the flower. This is why red roses turn "blue" when placed in water without a preservative or acidifier.

A microorganism growth inhibitor is perhaps the most important part of a floral preservative. Bacteria and fungi are everywhere and are ready to enter the cut surface of the stem and multiply. Prior to actual decay symptoms, cells of the water-transporting tissues can become blocked with microorganisms, inhibiting water uptake.

To aid the floral preservative in slowing down microorganisms, always clean the vase or container. Also remove all leaves below the water surface, as they soon deteriorate. Water and water uptake are major factors in keeping cut flowers fresh.

A process called "hardening" ensures maximum water uptake. It simply means placing the freshly cut stem in 110° F (43.5° C) water (plus preservative). Place in a cool location for an hour or two. Maximum water uptake is attained because water molecules move rapidly at 110° F (kinetic energy) and quickly move up the stems. Flowers at cool temperatures lose less water. In this one brief period while the water is cooling, freshly harvested stems, leaves, and flowers take up almost as much water as in the balance of their life.

Other Tips for Long-Lasting Cut Flowers

Check the water level of the container or vase daily and add water plus preservative when needed.

Keep flowers away from hot or cold air drafts and hot spots (radiators, direct heat, or television sets).

While both drafts and hot spots increase water loss, hot spots reduce a flower's life by speeding transpiration (water loss) and respiration (use of stored food such as sugars) and increasing development (rate of petal unfolding).

When away from home, move the flowers into the refrigerator or the coldest (above 35° F/1.5° C) spot in the house. Again, this will slow down water loss, respiration, and development.

Never store fruit and flowers together. Apples produce ethylene gas, a hormone that causes senescence, or aging, in flowers.

In summary, to keep cut flowers longer:

Flowering Plants

Inadequate light, high temperatures, and improper watering are the common causes of failure in flowering plants. These plants are grown in a greenhouse where the night temperature is usually cool, the air is moist, and light is ample. When these plants are brought into a dry home where the light is poor and the temperature is maintained for human comfort without consideration for the plants, the results are often disappointing.

Poinsettias

Poinsettias require bright light and should be kept away from drafts. A temperature between 65° and 70° F is ideal. Avoid temperatures below 60° and above 75° F. Keep the plants well watered but do not over-water. Newer, long-lasting varieties can be kept attractive all winter.

Reflowering a Poinsettia

The poinsettia blooms during short days. Starting October 1, exclude poinsettia from artificial light for 16 hours; either cover with a light-proof box each evening or place in an unlighted room or closet. Expose to full light during the day (eight hour days). Use fertilizer when new growth is visible. After 10 weeks of short days, the plants should reflower.

Easter Lilies

Keep the plants in a sunny place where the temperature does not fall below 60° F. Water when the soil feels dry.

After the plants have turned brown, cut off the stem at the soil surface. When the garden soil warms up in late May, move the plants outdoors. Choose a warm sunny place with well-drained soil. Plant the bulbs four to six inches deep (soil surface to the top of the bulb) in most soils and somewhat deeper in sandy soil. Easter lilies may bloom the first fall after being set outdoors. They are easy to transplant.

Fertilize several times during the summer and use a mulch to keep the soil moist. In the fall when the soil is lightly frozen, apply evergreen boughs or marsh hay around the plants. Keep this mulch on until new growth develops the next spring.

Azaleas

Azaleas require direct sunlight to remain healthy. A night temperature of 50° to 60° F will prolong blooming. Keep the soil moist. Azaleas can be planted in a shady spot in the garden during the summer months. Feed them with an acid fertilizer and examine them frequently, keeping plants watered during dry periods. Greenhouse azaleas will not survive Zone 4 winters.

Azaleas need short days and cool temperatures to form flower buds. If you can provide short days, after buds have formed, a six- to eight-week cool treatment is needed before plants will bloom. A well-lighted room with a temperature of 35° to 50° F is ideal, but hard to find in most homes. Unless you have the proper growing conditions for the azalea, you should not attempt to carry the plants over to the next year.

Cyclamens

Cyclamens require full sunlight and a night temperature of between 50° and 60° F. Flower buds will fail to develop if the night temperature is too high or if the light is poor. They require regular watering.

Plants can be carried over, but as with the poinsettias, homegrown plants are seldom equal to those grown by a commercial grower.

Gardenias

Gardenias grown indoors need special care and specific conditions. They demand an acid soil and should receive the same nutritional care as azaleas. The night temperature should be near 60° F and the humidity around the plant should be kept high. High temperature and low light intensity will result in flower-bud drop.