Vinca difformis

We also push the boat out with Vinca difformis varieties, which are often wrongly listed as Z9, but we have never lost any here. On very cold mornings (-8 or so) the foliage goes flaccid but recovers as soon as the temperature rises. Most of the forms (except Sardoa) grow to about 40 cm in the open, but much more against a wall or with something to scramble up. There only seems to be one white form, which we grow as ‘Snowmound’ (syn ‘Alba’, ‘Greystone Form’), the type is ice-blue and ‘Jenny Pym’ is almost a pure pink (slightly bluish in some light and when you try to photograph it with film). ‘Sardoa’ is the deepest blue, particularly as the flowers open and is more vigorous with a sparser habit. All flower almost all the year round, peaking in the autumn. If they a have a fault it is that they can be invasive – at least on heavy soil. Very underused and underrated.