A multicoloured loveliness

Until now I had not realized that one of the most colourful images from my childhood is, in fact, distinctly Mexican. My father grew dahlias commercially. The immediate environment of our house in Yorkshire was, during summer and autumn, a kind of deep lake of dahlias, row upon row of them. Everything about these plants comes back to me now as vividly as if I were actually walking through them or handling them.

What I didn't know was that the dahlia comes exclusively from Mexico, where it is a cheerful weed known - with more enchantment surely than the plain European adaptation of a botanist's surname (Dr. Dahl) - as ''cocoxochitl.'' Horticulture has radically extended the plant's range and shape, but in essence it is still an exceedingly vigorous, rather juicy-stemmed wildflower.

Dahlias are energetic producers of bloom, their colours specific, and surprising in their purity, in fire scarlet, or clean yellow, darkest purple with white tips, or white with creamy depths; warm pink, soft peach, or a dense velvety maroon. In form they can be almost overwrought, like floppy garden party hats. They can be radiating like stars or sea anemones. They can be trim like pompons. There are dahlias with long, curving petals in a mass like spiders overendowed with legs, and there are giant dahlias with flowers like enormous dishmops. The sheer size of these hefty, unruly heads intrigued my childhood imagination above all. They made me feel like one of the ''Hulsenbeck Children'' in a picture by the early German Romantic painter, Runge, who are towered over by sunflowers tall as trees. I felt equally dwarfed by dahlias, and amazed by their growing: how could the three-inch cuttings planted in the greenhouse only a few months before have now reached such proportions? Was there ever an individual flower so vast, so heavy, and so overcrowded with petals? I was as proud of the ''giants'' as if I had created them.

Such bigness was, in fact, encouraged by a nursery technique called ''disbudding.'' We all spent hours at it. I believe I could disbud a dahlia plant with my eyes shut: the tenderness of the small side shoots as they are taken off by thumb and forefinger is integral to my affection for the plant. Disbudded, the dahlia puts more effort into forming the main flower on its straight stem, making it larger and stronger.

Once fully opened out of the neat round buds, the finest of these flowers were cut, either for market, or for display at some impending flower show. They were kept overnight in large galvanized buckets in a dark old shed, a great concentration of brightness and unplanned colour, haphazardly glorious in the shadows.

No poet to my knowledge ever sang evocative praise to the dahlia's scent, which is not really surprising, as it doesn't have one. But its greenery does have a quite definite smell, evident when it is cut or broken, faintly acrid, I suppose, and for me instantly spanning years with its associations.

Nor have many painters made art out of the dahlia. Delacroix painted the flower, but the openhearted sensitivity of Christopher Wood's 1930 oil painting of ''Dahlias in a White Pot'' comes as close to the feel of the Mexican weed as any I can find.

Wood had a short career. He was English, but in many ways wished he could escape from the restraints on his imagination which he believed his nationality imposed. He was adult, but wished as painter that he could reexperience the fresh and artless vision of childhood. There is a simple straightforwardness about his paintings which is perfect for painting flowers. He was a friend of Ben and Winifred Nicholson, and his flower paintings indeed share characteristics with theirs: petals painted in bold strokes, never overworked; simple gatherings of flowers popped into a vase or jar with little apparent effort at ''arrangement'' but with a love that lets them behave almost as if they are still growing; and as background to the acutely sensed colours of the blooms, a subtle grey and whiteness, attuned to make those colours sing.

Wood went (as he felt a child would) straight to those things in a subject that seemed instantly most important. For an appreciation of the forms and colours of dahlias (here there are no ''giants'' though, only the simple heads of smaller varieties), his sophisticated innocence was ideal. He was a natural painter, and this potful of autumn flowers was represented by his brush with an uncomplicated ease which the dahlia itself epitomizes.