I love alliums and am considering adding some purple ones to my garden. There are several purple varieties that are near-identical, except for the hue. I’ve noticed that some alliums are more lilac/lavender in colour whereas others are more of a plum purple. When I’ve asked people who grow the lavender/lilac coloured ones that I like, they do not know the name of the cultivar. I’ve tried searching online without definitive information. I believe the lighter purple alliums are “Purple Sensation”, however, I have seem some photos of this cultivar that make it look dark purple or plum coloured.
1) Would you please provide colour descriptions for the tall purple spherical alliums (e.g. Purple Sensation, Globemaster, etc.)?
2) Does anything environmental (e.g. soil pH, shade/sun) affect the colour of a purple allium?
There is an astonishing variety of allium colours, from deep purple, nearly black, through all the lavender, lilac, mauve, and violet parts of the spectrum, to shades of rose and white. Purple Sensation is often described in bulb catalogues as “lilac-purple” while Globemaster is referred to as “purple”, the implication being that Purple Sensation is the paler colour. Since you have already searched the Canadian bulb suppliers online, it might be helpful to speak directly with some of these suppliers who may be able to give you a more definitive answer. It is often quite difficult to tell from a photograph the exact colour of a bloom. From a practical point of view, it may make sense to look at the current offerings from bulb suppliers and make your choice from what is available, especially as new cultivars appear frequently.
The Pacific Bulb Society’s website contains a comprehensive listing of alliums, but stops short of providing the kind of detailed colour description that you are looking for: https://pacificbulbsociety.org/pbswiki/index.php/Allium.
Most flowering plants – with the exception of hydrangeas – do not experience an altered appearance when soil pH is changed. They have an inherent color, genetically programmed, unrelated to the soil’s acidity. Alliums in general are not terribly picky – except about drainage, which is critical because their large bulbs are susceptible to rotting in wet conditions.
This article provides a good general description of alliums in the garden: https://www.finegardening.com/alliums-all-season-long#ixzz4jprxrGTn