Flowers for arrangements can be taken from flowering trees, shrubs, perennials, bulbs and annuals. Annuals are some of the best candidates for cut flowers since they produce lots of flowers over a long season.
Your vegetable garden is a great place to grow flowers for cutting: it will be more beautiful and you won't ruin your flower garden by cutting the flowers just as they are about to open.
Variety makes for interesting arrangements: mix flowers with different colors, sizes, shapes and textures. Foliage can play an important role in arrangements. Ferns, ornamental grasses, hostas and other leaves make wonderful additions to any bouquet.
When cutting flowers, take branches from the back side of shrubs and large perennials. With annuals and smaller plants, try to cut just a few flowers from each plant rather than taking all your flowers from one spot.
Some perennials that are to be used for cut flowers can be pinched back in the late spring (May to June) to delay flowering. Pinch some and let others flower early and you'll have more flowers over a longer season. Asters, chrysanthemums, bee balm, sneezeweed, balloon flowers and phlox can be pinched. Bulbs such as gladiolus can be planted in two-week intervals to extend their flowering season.
For some perennials, such as asters and phlox, thinning out the weaker stems early in the season gives you a nice healthy plant. You'll get more strong stems, larger flower heads and a sturdier plant. Flowers with strong, tall stems make the best cut flowers.
Most flowers can be cut when their buds begin to show color. There are a few exceptions: dahlias, phlox, zinnias, marigolds and chrysanthemums should be cut when the flowers are fully open.
Tips for Cutting Flowers
Cut flowers in the morning.
Take a bucket of cool or lukewarm water with you and put the flowers in the bucket as soon as they are cut.
If you cut flowers of different sizes, take out two buckets and separate the small and large flowers so that the small flowers aren't crushed; cutting flowers of different sizes and heights makes for interesting arrangements.
Use a sharp clean knife or scissors to make your cut.
Once indoors or in a cool, shady area of your garden, remove the foliage from the lower portion of the stem. Decaying leaves will contaminate the water and shorten the vase life of your flowers.
Re-cut an additional inch off the stem and place immediately in water.
Change water frequently and re-cut the stems if flowers start to wilt.
Use a vase that has been cleaned with soap and water. Add a few drops of household bleach to clean tough stains.
Flower arrangements last longer if displayed out of direct sunlight and away from heat.
Tips for Conditioning Flowers
The most important rule for conditioning flowers is to let them stand in a cool place, out of direct sunlight, in tepid water for several hours (preferably overnight). Add some cut-flower food; this will extend their bloom time by several days.
Cut all stems on a 45 degree angle. You are increasing the surface area for the water to get to the flower.
Woody stemmed branches from flowering trees and shrubs need to have the ends of their stems split. Split the bottom of each stem by making a ½ to 1 inch vertical cut.
For long-lasting hydrangeas, submerge them in a bowl of cold water (head down) for one hour to help firm their petals. Let the flowers drip dry, cut their stems at a 45-degree angle and place stems in warm water overnight.
Daffodils exude a clear sap that can kill other flowers. Cut these flowers and soak them separately in a vase for one hour before adding them to your arrangements. Warning: the sap can be a skin irritant.
Cut off the thick white section on the bottom part of the stems of bulbs for better water absorption.
Some plants, such as spurge, blood flower and poinsettia, contain a milky sap that can also be a skin irritant. To condition these flowers, sear the end with a match or dunk in boiling water for 15 seconds.
Plants with thin stems that tend to bend are best bundled together and left to sit for several hours in water before being placed in an arrangement. Tulips are a classic example of flowers that benefit from this treatment.
Another tip for tulips if they start to droop is to take a pin and prick a small hold in the stem just below the flower.
Some flowers, such as delphiniums, lupines and amaryllis, have hollow stems. Place a thick stick or wire up the stems or fill the stems with water and cover with a cotton ball at the base bound by a rubber band.
Cut carnations between the nodes on the stems for better water conduction.
Floral preservatives always help to extend the life of your bouquet. For a homemade recipe try 1 tablespoon of sugar, 1 teaspoon of household bleach and 2 teaspoons of lemon juice per 1 quart of lukewarm water. The sugar is food, the bleach keeps it clean and the lemon juice keeps it acidic which helps with the uptake of water.
Some perennials can be partially pinched back in late spring to spread flowering over longer period; photo of bee balm (Monarda didyma 'Purple Rooster') at NYBG by Ivo Vermeulen