Wire uses an imperial numbering system that relates to the diameter thickness of the wire, SWG, which stands for Standard Wire Gauge. We use just Gauge to determine the size. In the SWG system, the HIGHER the gauge number, the THINNER the wire. So, for example, 34 gauge wire is fine enough to use like thread, while 16 gauge wire is really thick and only just bendable by hand.
Here is a general guide to the different gauges and their uses:
30 gauge - for inserting into very fine, fairly small leaves.
26/28 gauge - for small, lightweight flowers and leaves
24 gauge - for small / medium size roses or other flowers, say, 1-1 ½” diameter max. Or for creating a fountain / explosion supporting shapes e.g. stars, hearts, letters, numbers etc.
22 gauge - For medium / large general flower use, similar to 24 gauge, but these are just a little stronger.
20 gauge - For larger flowers that need the support of a thicker wire, and to hold their position in a spray.
18 gauge - To hold very large, heavier flowers such as a full blown rose, calla lily, chrysanthemum etc. and which may be included in a spray of flowers and need to hold their shape.
Please also note no wires should be inserted directly into a cake – always use a posy pick. These are also available in different sizes to accommodate various sizes of wires or bunches of wires.