The single white alba rose is recorded as a sport on ‘Alba Semi-plena’. It is illustrated as such in Hortus Eystettensis (1613), with both single and double flowers shown on the same branch. ‘Alba Semi-plena’ forms plentiful hips, and presumably would produce single-flowered seedlings; as far as I know no-one has sown seed of ‘Alba Semi-plena’ and recorded the resulting plants. The single white rose shown here, with the bluish leaves of an alba rose, and white flowers with petals which do not overlap, may be one such seedling. It is also similar to some white dog roses with bluish hairy leaves, such as R. sherardii and R. mollis. Zone 3, surviving -25°C, and probably less.

The parentage of Rosa x alba is still in doubt. Hurst considered that it was a cross between a dog rose and a damask, and the general habit of the larger types is consistent with this theory. Graham & Primavesi (1993) give the parentage as R. arvensis x R. gallica. Both these parentages could result in the chromosome number 2n=42; the latter parentage would make the plant a fertile allotetraploid, which should come true from seed. A general survey of the DNA of cultivated roses shows the albas well separated from other groups. More definite information will be posted as it comes to our notice.

Photographed at the garden of Richard Rix Kent UK.