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Colour range within genus

Beautiful blue flowers most readily spring to mind when Meconopsis are mentioned. There are indeed many blue Meconopsis, although there are other lovely colours, such as the startling red of M. punicea, the clear yellow of M. integrifolia, the pure white of M. superba and the rich deep maroon of the newly discovered and exciting M. tibetica. Amongst the blue species are monocarpic M. prattii and M. aculeata, but more important horticulturally are the big perennial blue poppies, both species and garden hybrids.

The blue colour of the flowers of the big perennial blue poppies is rather variable. This variability never fails to interest Meconopsis enthusiasts and is much discussed. Some plants are relatively stable in colour. But for many others, this is not so. As a result, being precise about stating the exact colour for the different cultivars and species is often not straightforward. This conclusion has been reached after a number of years of detailed observations and discussion. Part of the reason for the difficulty in stating the colour categorically is that the flowers frequently show a continuum of variability. This occurs in the spectral range from pure blues to violets to purples. Close inspection reveals that colour variability is due to the petal tissues containing complex mixtures of pigments, and that the relative amounts of the different pigments may differ greatly.

The causes of this instability in colour are obscure, but must obviously be due to inheritance or to environmental conditions, or a mixture of both. Evidence for a genetic basis for colour variability includes, for example, the records on M. grandis in the wild by many plant collectors over the years. On their herbarium sheets, a striking range of colours, namely pure blues, mauvy-blues, purples and even maroon, are cited. For instance, on the herbarium sheet for the specimen of M. grandis GS600 collected by George Sherriff there is pencilled the note "Young flowers deep purple lilac. Fully open flowers blue tinged purple".

Variation in colour in M. grandis. The first three pictures are of flowers from three plants photographed in 2004 on the Arunachal Pradesh/Bhutan border, very near where George Sherriff collected his GS600 seed in 1934. The far right picture is of M grandis grown from seed collected in NE Nepal in 2000.

On the other hand, evidence for an environmental cause for colour variation has been frequently observed. For example, in a given year, or in a particular garden, or even a particular part of a given garden and different dates within the flowering season of the same garden, the flowers of a clonal cultivar such as M. 'Jimmy Bayne' or M. 'Huntfield', may be a pure deep blue with very little admixture of purple, or may be decidedly purple. So far it has not been possible to find hard and fast correlations between environmental factors and the colours observed - although speculation abounds.

It is known that plant colours through the range red to blue are produced by a class of pigments called anthocyanins, of which around 300 are known. These pigment compounds are sensitive to a many factors such as pH (acidity or alkalinity), light and heat. For example, an average anthocyanin is red in acid, violet in neutral and blue in alkaline solution. But careful observations have made it clear to the present author (E.S.) that colour variations are not simply due to the overall soil pH. However, it does appear probable that micro changes in the pH within the cells of the tissues of the flower petals are responsible for the differences in colours displayed. Even if this is accepted as a plausible theory, there are many unanswered associated questions, e.g. why do some clones (e.g. M. 'Jimmy Bayne') show more variability in colour than others (e.g. M. 'Slieve Donard'). This whole area needs detailed scientific investigations in order to come to an understanding of flower colour in the big perennial blue poppies.

It might be helpful for such an investigation to be aware of the speculations of Meconopsis enthusiasts about the causes of colour variations, based on their observations of such variations in the big perennial blue poppies. These include the effects of:

  • Geographical location and average climatic conditions of the area they garden in.
  • The type of soil in the garden, in particular its pH value.
  • Soil and air temperatures on the flower buds during early development while still below the soil (particularly below freezing temperatures), while the flower stem is lengthening and also air temperature, in particular, at the time of bud opening. Soil water content and air humidity might also have an effect.

Several examples of colour variation are shown in the pictures below.

Colour variation in the George Sherriff Group (GSGp) clones. The flower on the left above is a blue M. 'Ascreavie'. The middle picture shows from the left, two purple M. 'Ascreavie', a blue M. 'Jimmy Bayne'and a blue M. 'Huntfield'. The third picture (right) shows a purple M. 'Jimmy Bayne'.

M. 'Barney's Blue' (above,far left) is a George Sherriff Group clone which consistently passes through a range of colours from opening deep pink/purple, lightening to a paler shade before becoming blue. The remaining three pictures in the row are of three clones of M. baileyi each of which maintains its own individual colour, pale blue, deep blue and the rather indescribable rich plum of M. baileyi 'Hensol Violet'.

In M. 'Mervyn Kessell' (left) the buds invariably open deep purple and gradually change to blue over the next few days. In M. 'Slieve Donard' (Infertile Blue Group) (right) the flowers are almost always consistently sky-blue, although they may be a little darker shade of blue at opening.