The autumn show is only four months away (trust us, it’ll go quick) and as ever there will be a number of dahlia classes to enter. If you’re not used to growing or showing dahlias, there wide range of forms can be confusing. So if you don’t know your cactus from your collarette or pompon from ball, here’s a brief guide (courtesy of the National Dahlia Society) and examples of each one (click on each picture to enlarge them).

Decorative, cactus, pompon and single-flowered are usually the types that feature in our autumn show and we have provided a little more information on ball and pompon dahlias as they can be more difficult to tell apart.

Formal decorative

Decorative dahlias have fully double blooms showing no disc.  The ray florets are generally broad and flat and may be involute (curled or curved inward) for no more than 75% of their length (longitudinal axis) or slightly twisted, and usually bluntly pointed.

Cactus

Cactus dahlias have fully double blooms, the ray florets are usually pointed, the majority narrow and revolute for 65% or more of their length (longitudinal axis) and either straight or incurving.

Pompon

Pompon dahlias have fully double spherical blooms of miniature size (no bigger than 55mm in diameter except on the case of large poms which should not exceed 75mm) with florets largely involute along their length (longitudinal axis).

According to the RHS Horticultural Show Handbook, blooms are perfectly globular. Florets involute for the whole of their length, evenly and symmetrically arranged throughout the bloom and dessing back fully to the stem. Bloom facing upwards on a straight, firm stem.

Single-flowered

Single dahlias have blooms with a single outer ring of florets, which may overlap, the centre forming a disc.

Anemone-flowered

Anemone-flowered dahlias have blooms with one or more outer rings of generally flattened ray florets surrounding a dense group of tubular florets, and showing no disc.

Collarette

Collerette dahlias have blooms with a single outer ring of generally flat ray florets, which must overlap, with a ring of small florets (The Collar) the centre forming a disc.

Waterlily

Waterlily dahlias have fully double blooms characterised by broad ray florets that are slightly involute along their length (longitudinal axis) giving a saucer shaped appearance to the bloom. The depth should be not more than one third of the diameter of the bloom.

Ball

Ball dahlias have fully double blooms, ball shaped or slightly flattened.  The ray florets are rounded at the tips, with margins spirally arranged and involute for at least 75% of the length of the florets. For exhibition purposes miniature flowered varieties must not exceed 115mm and small flowered varieties must not exceed 170mm.

According to the RHS Handbook, blooms should be ball-shaped but the tendency towards flatness on the face of the largest cultivars is acceptable. Ray-florets compact and dense at the centre, symmetrically arranged, dressing back to the stem to complete the ball shape of the bloom. Florets compact and dense at the centre. Bloom poised at an angle of not less than 45 degrees to the stem, which should be straight and of a length and thickness proportionate to the size of the bloom.

Semi-cactus

Semi-Cactus dahlias have fully double blooms; the ray florets are usually pointed and revolute for more than 25% and less than 65% of their length and broad at the base and either straight or incurving.

Miscellaneous

Any dahlias which do not fall into type 1 – 9 inclusive and type 11, 12,13 & 14 e.g. Thistle Dahlias, etc. This group includes species dahlias.

Fimbriated

Fimbriated dahlias have blooms where the tips of the ray florets should be evenly split or notched into two or more divisions, uniformly throughout the bloom to create a fringed overall effect.  The petals may be flat, involute, revolute, straight, incurving or twisted.

Star

Star dahlias have blooms with a single outer ring of florets surrounding the disc.  Ray florets are uniformly either involute or revolute.

Double orchid

Double Orchid dahlias have fully double blooms showing no disc and have triangular centres.  Ray florets are narrowly lance shaped and either involute or revolute.

Paeony

Paeony dahlias have multiple outer rings of ray florets surrounding a disc, ray florets are flat or slightly involute at base and are flat or are to some extent revolute.

Photography judging at the Dedham Horticultural Society shows.

The photography classes are an important part of our spring and autumn shows, but have you ever wondered how they get judged? To help you create stronger entries, we asked judge Roy Laverick for his insight. He told us that he assesses each entry under three headings and awards points depending on how well they measure up.

Relevance (maximum 2 points)

“This generally results in an automatic two points for every entry, since it is unusual (but not unknown) to be confronted with a photo that does not comply with the class title for which it has been entered. I try to interpret this title as broadly as possible, but occasionally I just cannot see how the subject matter complies with class title, and the photo is accordingly barred from proceeding further through the judging process.”

Composition (maximum 5 points)

“In this area, I am particularly looking for photos that have a clear centre of attention to which the viewer’s eye is drawn. This will usually be towards the centre of the picture but need not necessarily be so. The way in which the subject matter has been framed within the viewfinder when the photo was taken, and subsequently during cropping (if carried out) is vitally important. Cropping can make or break a good photo and is something that should be considered very carefully.

“At every show I see otherwise superb photos, which are spoilt because they have been over-cropped. For instance, it is generally undesirable for a photo of a pot or bowl of flowers to feature blooms and/or stalks which pass out of the picture. Conversely, it is unfortunate if the prime subject of the photo is so small that it cannot be readily appreciated.”

Technical (maximum 5 points)

“Under this heading I am trying to ensure that the shot does not suffer from significant technical shortcomings, such as being out of focus in key areas or badly exposed (giving excessive lightness or darkness). I try to make allowance for photos that have obviously been printed at home, but if this process has resulted in noticeable ‘barring’ or ‘blurring’ (implying that the domestic printer is not up to the task being asked of it) the photo has little chance of being awarded a high mark.”

Choosing the winners

“The above marking process will sort the wheat from the chaff, but it is likely that a number of likely ‘winners’ will all have been awarded the same mark and this is now that a ‘tie break’ is applied. This takes the form of identifying which of the prints with a particular score has the greatest ‘wow factor’ and accordingly deserves for award purposes to be placed above its similarly marked competitor(s).

“‘Wow factor’ is very much a personal judgement and defies scientific definition. I am looking, however, for a photo that grabs the attention of the viewer as a result of being commendable for composition or technical ability and which also features spectacular colour and/or lighting. Sometimes there are like-marked photos, both of which have a high ‘wow factor’: that’s when the judge’s task becomes really difficult.”

So bear Roy’s tips in mind if you’re thinking of entering your photos in our next show.