Blue favourites spark white varieties

November 27th, 2015 | Plant Talk with Graham Rice | 0 Comments

Cobaea scandens 'Alba' - calamintsWriting about the ‘Marvelette’ calamints last week, it struck me that there are quite a few plants whose flowers are normally blue but from which, as with calamints, attractive white flowered forms have been developed.

That vigorous and long flowering annual climber the cup-and-saucer vine, Cobaea scandens, is a splendid plant for covering a sunny fence reaching up to 3m high or wide. The 50cm blue-purple flowers continue opening well into the autumn.

But there’s also an even more lovely white-flowered form, ‘Alba’ (left). Rarely seen, the flowers are actually a slightly minty white and held away from the foliage on long stems so they show themselves off brightly. (I know it says on the Mr F page that they turn purple – but they don’t, that’s the point!) Sow the seed indoors in February or March for the best results. ‘Lime Sorbet’, the white flowered double form of the wild blue columbine, also comes with a hint of green.

Lobelia is another classic blue-flowered summer flower with some very pretty white flowered varieties (below). These summer annuals for containers and edging flower for months – as long as they never dry out – ‘White Lady’  (below) is the neat bushy one for edging, ‘White Fountain’ is the trailing one for baskets.

Just one thing about these white lobelias. About one in one hundred plants will produce blue flowers instead of white – just pull them out.

Nigellas are also basically blue, but there’s a white form in the ‘Persian Jewels’ mixture and ‘African Bride’ is basically the white form of the blue-flowered Nigella papilosa (aka ‘Midnight’). It’s the same with cornflowers: wild cornflowers are blue, but there’s a white in the ‘Tall Mixed’ and ‘Polka Dot’ mixtures.

Finally the British native meadow sage, Salvia pratensis. This is a hardy perennial increasingly seen on roadside verges now that they are mown less often. The stout upright spikes of bright blue flowers are very impressive.

‘Swan Lake’ is a new white-flowered version that flowers from June to August, later if dead-headed. It will flower in its first year from a March or April sowing, although the first flowers will be a little later in its first season. It also features more stems and more flowers per stem than the usual blue form and is much appreciated by bees. Lobelia 'White Lady'- calamints
There’s more on blue nigellas, and white, in an earlier post here on the Plant Talk blog.

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Is one of our best known gardening writers. A graduate of the Royal Botanic Gardens, Kew, Graham was previously Gardening Correspondent of The Observer.
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