The following are the 10 main classification groups of Dahlia hybrids

Single-flowered (Group 1): As the name of this group suggests, these hybrids have a single ring of ray petals (sometimes 2) with an open center. Most singles are small plants usually growing no more than 18 in (45 cm) high, so they are ideal for bedding and are often sold as seed strains. ‘Yellow Hammer’ is a popular bedding variety with bronze foliage and rich yellow flowers.

Anemone-flowered (Group 2): Not many of this group have been bred as yet. They have one or more rows of outer ray florets and instead of the yellow center, these tiny flowers have mutated into outward-pointing tubular florets.

Collarette (Group 3): This group, once again becoming popular, has a single row of 8 outer large florets which are usually flat and rounded at the tips. Then comes a row of shorter tubular, wavy florets often in a contrasting color and finally the normally yellow center.

Waterlily or nymphaea-flowered (Group 4): These fully double-flowered dahlias have slightly cupped petals that have a more than passing resemblance to their namesakes, the waterlilies. The overall effect is of a flattish flower. ‘Cameo’ has white flowers with a cream base; ‘Gerrie Hock’ has pink waterlily flowers on strong stems and is popular as a cut flower.

Decorative (Group 5): This group are fully double-flowered dahlias with no central disc showing. The petals are more numerous and slightly twisted making the flower look fuller than the waterlily types. This group, which can produce some truly giant forms, may be subdivided into formal decoratives and informal ones. Informal decoratives have petals that are twisted or pointed and of an irregular arrangement. ‘Hamari Gold’ is a giant decorative with golden-bronze flowers. ‘Evening Mail’ is a also a giant decorative. ‘Majuba’ is a very free-flowering compact, medium-sized decorative dahlia bearing deep red blooms on strong stems. Large informal decorative types include ‘Almand’s Climax’ which has lavender flowers with paler tips; ‘Alva’s Supreme’ with yellow flowers; ‘Golden Ballade’ with deep golden flowers and ‘Suffolk Punch’ with rich purple flowers.

Ball (Group 6): As the name suggests these dahlias are full doubles and almost ball-shaped. Miniature, small, medium and large forms are available. ‘Rose Cupid’ is a medium-sized ball dahlia with salmon pink blooms; ‘Wotton Cupid’ is a dark pink miniature.

Pompon (Group 7): These are similar to ball dahlias but even more globose and usually not much more than 2 in (5 cm) across. They are sometimes called ‘Drum Stick’ dahlias. ‘Buttercup’ is a yellow pompon form.

Cactus-flowered (Group 8): This group of fully double-flowered dahlias have long, narrow rolled petals giving the flowers a spidery look. This group can be divided further by size as well as into classes with straight petals, incurved petals or recurved petals. ‘Hamari Bride’ is a medium white form.

Semi-cactus (Group 9): As the name suggests this group is close to Group 8 but the petals are broader at the base and less rolled back at the edges. ‘So Dainty’ is a miniature with golden bronze and apricot flowers; ‘Brandaris’ is a medium form with soft orange and golden yellow flowers; ‘Hayley Jane’ is a small form with purplish pink flowers and white bases; and ‘Salmon Keene’ has large salmon pink to golden flowers.

Miscellaneous (Group 10): This category consists of small groups and unique forms of dahlias that do not fit into any of the above groups. If breeders increase the numbers in any of the forms in this category, they will probably be split off to form new groups. Under this heading can be found such forms as orchid types which are single with revolute petals: ‘Giraffe’ with its banded yellow and bronze flowers is an example. The star dahlias are also single in appearance and produce very pointed, widely spaced petals. Peony-flowered dahlias, which are still kept as a separate group in some countries, usually have one or two rows of flat petals with a center which can be open or partly covered by small twisted petals; examples of this form include ‘Bishop of Llandaff’ with its brilliant scarlet blooms above its beautiful deep burgundy leaves, ‘Fascination’ with light pinkish purple flowers and dark bronze foliage, and ‘Tally Ho’ with deep orange flowers and gray-green leaves, tinged with purple.

Hardiness zone from 8 To 10
Plant Height approx. 35 - 200 cm
Flowering colors: Mauve, Pink, Yellow
Flowering season: Autumn
Garden type: Bedding Plant, Small Garden
Position: Sunny, Semi-Shaded
Soil: Medium Loam, 

Dahlia

Cultivation: Dahlias are not particularly frost resistant so in cold climates the tubers are usually lifted each year and stored in a frost-free place to be split and replanted in spring. Most prefer a sunny, sheltered position in well-fertilized, well-drained soil. Feed monthly and water well when in flower. Increase flower size by pinching out the 2 buds alongside each center bud. All, apart from bedding forms need staking. Propagate bedding forms from seed, others from seed, cuttings from tubers or by division.

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