dwlogo.gif (8261 bytes) THE GROWING WORLD OF DAHLIAS

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by Dave Bates

introduction - botany

The dahlia is a member of the botanical family called the COMPOSITAE. The epitomy of this family is the daisy. The family differs from other families in that the flower is made up from a number of units called florets, each of which is a botanical flower in its own right. The florets are of two types. Disc florets are the yellow tubes in the centre of the 'flower', forming the eye, and ray florets are the flatter 'petals' surrounding the mass of the disc to form the outline of the flower. Modifications to the structure and colour of these floret combinations provide the enormous variety of shapes and sizes of flowers of the Compositae family which also includes Michaelmas Daisies and Chrysanthemums.

sunflower type

The leaf habit of the daisy provides a whorl or rosette of leaves with virtually no stem. Other leaf patterns occur within the Compositae, and the dahlia belongs to the same genus as the Sunflowers, the Helianthoideae, with leaves typically paired opposite each other on the stem that varies from 12 inches to 30 feet in extreme cases, although the norm is around four feet. The botanical classification is based on the original Dahlias, the various species found growing naturally in various habitats around the world, but predominately in the Mexican area.

where it all began - the species of dahlias

The original species of dahlias were all made up of an eye of disc florets and a single row of ray florets to provide the outline. There are several recorded species, and these provide clues to the present day variation and limitations of the flower. Dahlia arborea and Dahlia scapigera both have white flowers; Dahlia excelsa has purple flowers; Dahlia coccinea (also known as Dahlia Zimpanii) and Dahlia Juaerzii both have scarlet flowers; Dahlia imperialis has white and rose flowers; Dahlia Merckii has lilac and white flowers while Dahlia gracilis has various shades of red , orange and yellow.


Some degree of crossing took place (although the species parentage is not known) and gave rise to the hybrid Dahlia variabilis which has flowers of various colours and tints. When seedlings were first grown in Madrid, there were three distinct forms which became known as D. rosea, D. coccinea and D. pinnata which was semi double. Some years later, a French gardener had three species D. coccinea, D. purpurea and D. crocea although the latter two are thought to be D. excelsa and D. variabilis. After a few attempts at growing from resulting seed, he eventually produced three plants which had fully double flowers. Records are not very clear, but D. variabilis appears to be the main parent of all modern day dahlias and being a natural hybrid has given rise to many variations.

The ray florets or petals have twisted and turned in many directions to generate the variation in floral structure seen today. The basic ray floret can be considered as a flat piece of paper. If the edges of the paper roll inwards, the petals are called involute, or if they roll backwards they are called revolute petals. If the entire petal bends inwards, it is known as incurving, or if outwards known as reflexing. Indeed some petals show several of these curving characteristics at the same time, serving to further widen the possibilities for overall shaping which we will examine further.


The vast number of modern dahlias derived from the species are similar in that they have a single row of ray florets surrounding the normally yellow disc. For this reason the are known as SINGLE dahlias. Many of the species dahlias and the single cultivars are very attractive in their own right, but do not fit the exhibition mould and have tended to be ignored. More often than not, the seedling growers reject single blooms out of hand as having no exhibition potential and consequently there are not as many available as there could be. Most of the survivors are grown as bedding dahlias where the shortness of the plant balances the smaller sized flowers of the single cultivars, and who can forget seeing magnificent beds of mixed dahlias in parks and gardens, with the great variety of colours massed in an area.


In some instances the tubular disc florets became elongated and took on colours while the ray florets were only marginally larger than previously. This gave rise to a pin cushion effect on the disc of the flower, and the type was called ANEMONE FLOWERED. At
one time there were a large number of these types around, but the numbers have dwindled and whilst there are about twenty recognised in Holland, only four are included in the Classified Directory, including Comet and Scarlet Comet. Sadly, no UK specialist nursery supplies anemone flowered dahlias, but odd ones are still available in the plastic bags.


An alternative development occurred in Germany when the eight ray florets were modified such that the larger floret developed smaller attached florets to give the effect of a small collar inside the outer circle. The petals of the outer circle are often pointed, but may be rounded in some varieties.In some cases the collar was the same colour as the outer ring, and in others the colour change was quite startling. These became known as COLLERETTE type dahlias. They have a particular attraction, with many of them being quite old. Numbered among this type are the all yellow Clair de Lune, Chimborazo (dark red petals with a yellow collar), La Cierva (Purple and white petals with a white collar).


In the early years of this century, further development of the ray florets of the semi double flowers (those with two or more rows of ray florets) gave rise to the PAEONY type flowers, the most well known of which today is the Bishop of Llandaff. The sizes of the individual petals within this group increased, and eventually gave rise to the earliest giant flowered varieties.


An alternate development of ray florets gave rise to pointed petals, with one or two rows of florets making the flower resemble a star. The ray florets were usually incurving to give a cup-like structure to the bloom. These types were more popular in the mid part of the century, but are virtually unobtainable now as fashions have changed.

single orchid

In some instances, the eight ray florets elongated and became slightly involute at the tips. These types have become known as SINGLE ORCHIDS and they are well represented in the USA although very few examples exist in the UK. Among the more popular varieties of this type are Marie Schnugg and Starbright which is a vibrant orange in colour.

doubles are tops

All the previous types arose from the development of the ray florets, but still leaving the central disc exposed. However in many instances the development of the ray florets has completely hidden the central disc, giving rise to the fully double types.

double orchid

A much greater number of ray florets, still tending to be involute at their tips or in some instances for the whole length of their petals has given rise to a specific form beloved of flower arrangers. These are known as DOUBLE ORCHID FLOWERED varieties. The more established popular varieties of these are Jescot Julie in shades of bronze and orange, Giraffe in mottled shades of orange and its colour sport, Pink Giraffe. A newer variety originating in Japan in delicate shades and blends of light pink and white is Tohsuikyoh which has a larger and more powerful flower than the older varieties and will surely become very popular with devotees of dahlia arrangements.

water lily

An increase in the number of rows of ray florets, but not by a vast amount has given rise to a form of flower which is fairly flat at the back, and resembles the water lily. As a result it is known as the WATER LILY type or NYMPHAEA in some countries. Members of this type have flowers ranging from 3inches to 8inches in diameter, and are usually delicately petalled. Typical examples of this group are the classic yellow Glorie van Heemstede from Holland, the bright yellow Fern Irene, and the light pink Figurine from Australia, while the red incurving Christopher Taylor has proved very popular with the general public. Although bright red cultivars of this type are few and far between, the last few years has seen the arrivals of Malham Portia and Abridge Robin, both very attractive flowers in a colour that pleases many.

ball & pom

Complete involution of the ray florets for more than half their length and rounding of the tips with the florets arranged in a whorl giving a rounded shape gave rise to the modern day BALL dahlias, once known as the double show dahlia. These are typically 3inches to 6 inches in diameter, while their smaller neater cousins are called POMPON dahlias, but are now only up to 2inches in diameter. (The large pompons
which were up to 3 inches in diameter have become indistinct from the smaller ball dahlias.) They normally have plenty of petals in the centre. Typical among the ball dahlias are the light pink Wootton Cupid, very floriferous and ideal for the garden, Risca Miner a larger purple flower and Opal a light pink and white flower. Although the double show dahlias were very popular, and the numbers of cultivars prolific, the count of modern day cultivars is only small. Among the pompons are a number of varieties raised by the late Norman Williams in Australia, all containing Willo somewhere in their name. Popular are Willos Violet, Willos Surprise and Pop Willo , as well as the purple Moor Place and light pink Hallmark. There are a further group of pompons available via garden centres which do not conform to the Pompon type described above. Typically the petals and blooms are larger, as well as smaller in number giving a looser bloom. These are often known as dutch poms. A further point of interest regarding the pompon types is the colour. Among most types there is a wide spread of colours ,with a current tendency to domination by white, yellow and oranges but in the pompons these are quite rare and the dominant colours are purples, mauves and pinks.


A development from the Paeony Dahlias which became fully double gave rise to the DECORATIVE dahlia which typically has broad, flattened ray florets with bluntly pointed tips. These form one of the major groups for the showman and nowadays vary from three to fifteen inches in diameter, and they have far more rows of ray florets than the water lily types generating a flower where the petals dress back to the stem creating a more globular outline. The florets are sometimes slightly involute at the base, and sometimes slighty revolute at the tip, indeed both these characteristics appear on the florets of many of the giant flowered varieties. In recent times, the classifiers have allowed flowers with a greater degree of involution to be considered as decorative dahlias, and the variation between ball and decorative dahlias has become less distinct such that the degree of pointing at the tip of the petal has become the main distinction in many cases.

In some of the varieties, the petals reflex significantly and produce a flower with a very distinctive ball shape. Typically these are flowers naturally around the six to eight inch diameter and among them are Edna C, Evelyn Foster, First Lady and the much newer Formby Supreme.

informals and formals

The overall effect of the petal lay of the ray florets is varied. In one case they are regularly arranged giving a distinct pattern, and these are known as FORMAL , whilst others have them irregularly arranged and less involute or twisted and are known as INFORMAL. Typically the more formal flowers are those in the smaller sizes and include varieties such as Nina Chester, Honeymoon Dress and Abridge Taffy, while the giant sized flowers include more informal types such as Hamari Gold and Hamari Girl.

cactus and semi-cactus

The revolution of the ray floret to form a quill like structure gave rise to the 'spiky dahlias' known as CACTUS flowered dahlias. Like the decoratives the number of florets was such that a complete globe is formed as the florets dress back to the stem. Sizes vary from 3 to 12 inches in diameter, but very few exceeding 8 inches are available, the majority being in the 4 to 6 inch range. These include the classic Klankstad Kerkrade and its derivatives, with their straight petals and Shirley Alliance plus the newer Kiwi Gloria whose petals incurve. There are several where the quilling of the ray floret is only at the tips, and the base is broad like a decorative dahllia. These in-between forms are called SEMI-CACTUS. These also vary from 3 to 14 inches in diameter but the majority are above 7 inches in diameter unlike the more refined and quilled cactus dahlias. Typical examples are straight petalled Eastwood Moonlight and Reginald Keene and the incurving petalled giant Daleko Jupiter.


In one specific case, the ray florets are long ,narrow and quilled. As they unfurl from the centre they give the bloom the overall appearance of a developing Chrysanthemum. One example of this type is Andries Wonder from Holland which was awarded a Highly Commended at Wisley in 1955 but this no longer seems to be available. In the mid eighties, a further example appeared from Japan, called Akita .Indeed at one show some blooms of this variety were included in a basket display and one member of the public complained that it was a dahlia show and why were chrysanths allowed!


Even with this array of different types of flower there are still some overall forms where the floret developments are not able to be grouped for one reason or another. They are lumped together as MISCELLANEOUS types. There are numerous types of flowers that are in-between classifications. In the smaller types the distinction between ball and decorative is not always as clear as it should be, while among the much larger blooms, the distinction between decorative and semi cactus is similarly unclear.


The ray florets of some varieties, mainly cactus types may be split at the tips. This is known as laciniation or fimbriation. It gives rise to a very attractive overall form like a powder puff. These types are very popular in all parts of the world except the UK, where there were many up to the middle of the century, but now only few including the yellow Promise and the red Apache. Cyril Higgo of South Africa developed a good breeding line of fimbriated varieties, and these have provided a firm foundation for the further development of the types throughout the world. Fortunately there are people in the UK trying to resurrect these types, and in 1993 the Classified Directory included Marlene Joy, a beautiful white variety with the fimbriated tips in dark pink. This is hopefully the first of many new ones that will appear on the scene.

flower sizes

The overall sizes of the flower vary enormously. The smallest flowers sometimes barely an inch across are LILLIPUT dahlias (these are also known as TOPMIX dahlias in many countries and as MIGNON in Europe). Popular varieties of this type of flower include Sweetheart, Samantha, and Peachette. The flower formation is usually single but some double types do exist. The major size variations occur in the decorative, cactus and semi-cactus types and size names have been generated to help describe the blooms of these types. Miniature flowers are up to 4" in diameter, Small from 4" to 6" , Medium from 6" to 8", Large from 8" to 10", while any greater than 10" are known as Giant flowered. It is interesting that pure cactus types are numerous in size ranges up to 6 inches , scarce up to 8inches and almost non existent in larger sizes, while the reverse is the case with Semi-Cactus types. Water lily types exist up to medium size, but the vast majority are small flowered. Ball flowered dahlias are miniature or small with very few varieties approaching 6 inches in diameter, while Pompons are specials at up to 2" diameter.

variation in colours

Not only is there variation in shape and size, but in colour too. No flower species with the possible exceptions of pansy and polyanthus have flowers with all three prime colours in pure form, ie red , yellow and blue. For many years, indeed centuries, plant breeders have sought the Black Tulip, the Blue Rose, th e Yellow Sweet Pea and the Blue Dahlia. The clue to the lack of blue colour in the Dahlia results from the building bricks of the species types. They provided light pink and yellow; dark pink and white; and shades of red and orange. Mixtures of these floral pigments will give many colours but the pure blue pigmentation is absent, hence anything tending to blue is a variation in one of the other colours, normally dark pink. The pigments provide self coloured flowers, and mixtures of colours. The mixed types are usually blends of two colours, but sometimes instead of the colours blending, there is a distinct break between the colours of the florets. These are called bi-colours, and among them are Match (white with purple tips), Edinburgh (purple with white tips) and Jessica and Aloha (both yellow with red tips). Some varieties such as Betty Bowen have one colour on the front of the floret and another on the reverse. A further variation with two or more colours is the variegated colours, one colour in the background with blends and streaks of a second colour throughout the area of the florets. Sometimes the colour of the flower changes through a mutation known as sporting. This can produce some most peculiar effects. In my garden, I have had a ball with one half white and the other half yellow, another with the top half red and the bottom half yellow, and a sport of Willo's Violet that was dark and light in a checker board effect. The effect of a sport is normally only noticed in colour changes, but it can also affect formation, leaf formation height and a host of other characteristics.

what about the foliage

Its not only the flowers that provide variation and interest in Dahlias. The foliage is another source of difference. Various shades of green exist, along with some shades of bronze such as the foliage of David Howard and Bishop of Llandaff. One notable breeder, George Brookes of Inca fame spent many years trying to produce a dahlia with red foliage but sadly he hasn't finally succeeded. The presence of virus can induce variegated foliage, and while it is conceivable that natural variegation could exist, no dahlia grower would risk retaining such stock, assuming that it carried a dreaded virus. The foliage is sometimes thin and sometimes thick and leathery. The leaves are serrated at the edges, but the degree of serration varies enormously, from an
almost smooth edge to a deeply toothed one. The normal, ovate leaves can be simple (single) or combined in a pinnate form (several leaves off a central leaf stalk) on the same plant depending on the age of the plant when the leaves developed.. The large leaves of some varieties can be compared with smaller leaves in the pompon types and even with feathery leaves in some other variations. Even if there were no flowers, a dahlia bed could be made to look interesting by planting an appropriate selection of varieties with differing types of foliage.

heights of plants

Height variation is significant. One of the species dahlias grows so tall that the Indians use its hollow stems as water pipes, while some of the lilliputs only grow to a height of 6". Most standard varieties grow to between 3ft and 4ft 6inches, while there are many bedders between 12"and 2ft in height. More often than not, the flower size on these plants is balanced to the height and stem size, after all a 15"diameter giant decorative on a thin 12" high plant would be inadequate for any use in the garden or exhibition. Selection by breeders has removed anomolies like this, and only varieties where the blooms are balanced to the plant sizes have survived. The girth of most types is balanced to the overall height, but some bear more side branches than others making them more or less dense bushes. For instance Eileen Denny only has a few side branches and provides a far lighter framework than Grenidor Pastelle. Typically, lilliputs are grown in pots or at the front of a border. Their height and growth formation make them ideal for small gardens and patios, and well grown and cared for it is possible to have plants up to 3 feet in diameter in a good sized pot.

where next - scents?

A friend who is very keen on sweet peas once said that dahlia growers had no sense, or was it no scents? It would be pleasing to say that the dahlia also provides a variation in sweet scents, but this is not the case. I know of a sport of Daleko Gold that had a pleasant scent, which was retained for a second year,but unfortunately the stock was lost in the ravages of a severe winter frost.

The most likely source of an altogether different form of flower is Japan. They are less concerned about the exhibition form of flowers and like to pursue the unusual, whereas breeders in other parts of the world are 'educated' to reject anything that does not conform to the current fashion.

However, the dahlia world has progressed over the centuries, sometimes due to a stroke of fortune in a specific crossing, or the activities of an educated bee or to the foresight of a lucky grower. No doubt this trend will continue and the variations in all aspects of the dahlia will continue to proliferate and provide wider interest to all lovers of the flower.

This article was written for the NDS Annual

Last updated February 02, 2005

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