Of course we all know that it is possible to put flowers into a vase without having a plan in mind. Sometimes a design may emerge without conscious direction, but you are more likely to have a satisfying and effective result if you have a design in mind. This is either suggested by the position in the room where it will finally rest, or perhaps by your container or the colour scheme of the room.
Flower Arranging Tips
For instance, you might make a triangular flower arrangement for the centre of aside table, whereas a curved arrangement would appear more suitable for the edge of a mantel. A low bowl, dressed so that it can be seen with equal pleasure from all sides, would be ideal for the casual or coffee table, but a rectangular design would prove a better complement to modern furniture. Again you can imagine that a full buxom bouquet in a copper urn would appear ideal if placed on the top of an oak chest in a Tudor style home, but try to visualise the pleasure you would experience by using one of the exquisite ewers of the Georgian period for a softened vertical arrangement, to be placed in a Regency room.
These, and many more, ideas will come to you, so try to look at your setting as though it were a frame and compose your flower decoration within this space. The frame, as you see it, may be one corner of the room, or just the mantelshelf. It may be a low table on which a lamp habitually stands. So for the mantelshelf, take everything on it into consideration. It may be that a clock is the centrepiece of attraction, then why not place some flowers each side, in containers and using colours that will combine with the clock ; this makes for good composition within the framework of your mantel shelf. Similarly, on the low table, you might compose this picture by adding a low flower design in a small round bowl, made of flowers that combine or contrast with the colour of the lamp shade.
Even the shapes of your containers all play a special part when composing within a frame. For instance, a round bowl would be used for a roundtable, an oblong shaped container would be more suitable for a long refectory table. A plinth urn is excellent for the centre of a side table backing a wall, for with nothing else but the background to detract our attention the beauty of the urn can be seen. Small glass goblets are charming and are usually in good scale when placed on casual wine tables, filled with delicate flowers.
But in all compositions scale is of great importance. I once entered a charming old house, and in the low-ceiling drawing room I noticed a tall vase filled with a dozen very long stemmed gladioli. They were meant to appear casual, but gladioli with their stiff, straight stems never seem to give the appearance of being casually placed. They just looked straggly and untidy, but in this case it was the scale that upset me, for the height and weight of these tall gladioli were all out of proportion for the low-ceilinged room, which I thought would have looked better decorated with a smaller arrangement, in scale with the height of the room, and made with a smaller type of flower, or, if gladioli were the only ones available then they could have been cut down, and some of the lower florets could easily have been removed and used as an extra arrangement in a shallow dish on the dining table.
If you know what shape or size design you wish to make, you can adapt your material accordingly. You can cut it shorter if you wish, or separate it if it is too full, or even ply it with your hands to make a bend if it is too straight. Trim one side of a branch if you wish swerves to flow one way only. In fact, ‘ Know what you want to do and why ‘ is the answer to a lot of the problems, and then adapt your material to your desires.

