In Australia, blooms are assessed on six main criteria - condition, form, stem, colour, size and staging.
- Blooms should be fresh and mature – firm, not drooping, clean and free of blemishes such as damaged and missing florets. Centres of double cultivars should not be open or hard and green. Pollen on open-centred blooms should be fresh.
- Blooms should conform to the form standard for the type. See the type pages under Dahlias for Showing for the type standards. The face should be symmetrical and circular without gaps or uneven spacing of the florets.
- Stems should be straight, not weak, and in proportion to the bloom.
- Colour should be clear and bright, not faded, and consistent. A bi-colour bloom should have two clearly defined colours on the faces of the florets forming a regular pattern with even tipping. A blend of two or more colours should merge gradually and evenly.
- The diameter of the bloom should conform to that required by the competition class. See the standard sizes below.
- Blooms should be staged to face the viewer with at least 160mm between the centre of the bloom and the top of the container.
A points-based system is used to identify faults and assess blooms. See the Point Judging Guide Sheet.
In classes for vases of multiple blooms of the same type, the blooms should be identical and facing at the same angle.
Championship class requirements vary from show to show. The host society specifies the required number and variety of types and sizes and the mix of single and multi-bloom vases. Balance in staging is always important.
Floral Arrangement classes do not place importance on compliance with standard forms or sizes. The State Show Container and Display Sections criteria are:
- Appeal (30 points): Creativity, including skilful use of colours, varieties and types.
- Arrangement (30 points): Creativity of design, stage techniques, balance of the exhibit and artistry of the complete display.
- Condition and Freshness (20 points): Blooms and foliage should be clean and fresh. Blooms are judged on their face value only, not depth. Points are deducted for blown centres or misshapen flowers.
- Use of Colour (20 points): A pleasing harmony or a contrast of colours.
The Australian Standards define five distinct sizes:
- Giant 260mm and over
- Large 210mm and under 260mm
- Medium 160mm and under 210mm
- Small 120mm and under 160mm
- Miniature under 120mm
The allowable and required sizes vary by type:
- Formal, Informal and Semi Decorative Dahlias, Cactus, Semi-Cactus, Exhibition Cactus and Fimbriated Dahlias come in all five sizes.
- Ball Dahlias may be Small or Miniature.
- Pompon Dahlias must be under 50mm.
- Miscellaneous Dahlias may be under 160mm or over 160mm.
- All other types must be under 160mm.