All your effort in flower arranging will not be worth while if the flowers are not long lived. The most important factor for lasting freshness is that all the materials used should be properly hardened before use. This means that all should be quite turgid and taking water well before they are placed in an arrangement.
Part of an arranger’s normal equipment should be a series of buckets or similar vessels, some deep for tall stems, some shallow to take short-stemmed flowers, for although they need a deep drink it is not wise to submerge blooms. Nor is it wise to crowd them together for this might damage some and cause others to lose much of their colour.
As soon as possible after they are gathered (or as soon as they are brought home, if bought) stand the stems in deep water. This should cover any foliage on the stems. Let them stay there for at least an hour and longer, even overnight, ifpossible. Plants give off water from their leaf surfaces. This is not a great problem when roots and veins are rapidly conveying it through the growing plant, but it does sometimes cause difficulties when the flowers have been cut and the roots are no longer serving the plant. By covering the leaves with water respiration is cut down and the stems will become turgid.
To ensure quick uptake of water all but hollow and very fleshy stems should be split at the base upwards in. or more, according to the length of stem. This exposes the soft inner tissues. It also expels any air present which might otherwise tend to cause a lock in the stem tissues and prevent water being drawn up. To prevent flowers from wilting inexplicably (as some do after arrangement even though they have had a deep, long drink beforehand), it is advisable that the water into which they are stood for the preliminary drink should be warmed to about 70°F or 21°C. In fact I use tepid water also when I begin an arrangement and again for topping up; rain water is best.
Singeing and scalding: For a variety of materials speed and certainty of water uptake may differ widely. Some plants such as acacia or mimosa apparently cannot absorb water at all. Only humidity around the flowers and foliage keeps them fresh. You can, for example, keep mimosa fresh and fluffy for days, even weeks, if you place it under a sealed glass dome. This is a plant that is happier in a block of moist plastic than in water.
Those stems which exude a milky juice or latex, euphorbias or spurges for example, cannot take water until this flowing juice coagulates. The easiest way to hasten this is to singe the stem ends over a flame as soon as possible after cutting. Any stems which are shortened for arrangements after the singed ends have been given a drink should be re-singed. It is useful to have a candle burning nearby when using these flowers. This treatment also applies to poppies of all kinds.
Any flower which fails to become turgid when treated as above should have its stem ends stood in 1-2 in. of boiling water and allowed to remain in it until it cools, by which time it will be firm and swollen. Stem ends thus treated often become blackened and sometimes soft. This portion may be cut away if the stem has to be shortened for arrangement; once it has become turgid there should be no need to treat the new stem end. Some materials which are notorious for wilting, such as some grey or silver leaved shrubs, take water best if a little of the old wood is left on the stem. Immature tissues just do not seem to be able to drink well.
Retarding bacterial activity
Certain preservatives and nutrients are helpful to maintain freshness. There are several proprietary brands on sale. Most of these contain some glucose which seems to be appreciated by most flowers. Alternatively you can use one level teaspoon of glucose, a lump of sugar or one saltspoon of honey to a pint of water. In arrangements of fresh shrub and tree materials, especially those such as blossom in bud or Christmas evergreens which are expected to stand for some weeks, use a little of any good soluble plant food, sufficient to make a very weak solution. Since metals seem to inhibit bacterial activity, there is some validity in the old advice to place a copper coin in the container. Alternatively dropping an aspirin tablet in the water tends to discourage or delay bacterial action.
Foul water will help kill flowers and will also sometimes discolour them. So always strip the leaves from the portion of stem which is to remain under water even though it may speed up the intake of water. Avoid hammering or crushing woody and fibrous stems for the same reason. The foamed urea plastic stem-holders already mentioned contain formaldehyde which is a form of disinfectant and so these help to keep flowers fresh.
Contrary to a belief which is still widely held, flowers should not be taken from their vases each day to have a piece of stem cut away. Neither should the water need changing each day if the proper treatment has been given to the flowers. But of course the level of the water should be topped up in case it evaporates to danger level.