Plumbago, or Cape Leadwort (Plumbago auriculata). It has to be one of my favourite flowers and there was never any doubt that it would pop up as one of my "Gardener's Bloom Day Flowers of the Month" some time this year. But it nearly didn't make it. Last year plumbago was in full bloom in June here. This year, with the cold wet spring we had it was late. June came and went, but there was no sign. And then in July I started noticing it blooming on other people's balconies.
There's a lot of contradictory information about the plant on the web. You'll read it thrives in the heat and the sun. Or that it should be protected from too much direct sunlight. That it can't take temperatures under 7°C. And that it will survive frosts. That it does well in poor soil. That it likes a rich compost. The list goes on.
In my experience it's a tough little plant that will grow under a range of conditions. I don't think there's any doubt that it likes the sun (it's native to South Africa after all). But I find that its also fairly hardy. I cover mine in winter but most of my neighbours don't and it seems to survive, despite the fact that temperatures may be well below zero at times.
I don't give mine any special treatment and, apart from the lack of blooms this year, have never had problems. It's grown in ordinary soil, and fed and watered much the same as any other plant. As the water here is very hard, plants which are really particular about acidic soil just don't make it under normal watering conditions, but I've never had problems on that front.
Another reason I may not be getting many blooms this year is because I didn't prune this spring. Plumbago blooms off the new wood, and can be cut back fairly enthusiastically to encourage new growth and keep it in check. In a garden it can reach three or four feet high, so in a container it needs a bit of restraint.
It's also one of the few plants I have which doesn't seem to suffer from red spider mite - or anything else for that matter. It's poisonous, and for those of you who have the problem, deer will avoid it. (That does come from the net - we don't get many on the balcony.) It does attract butterflies, though as I've never had caterpillar damage i presume it's just for the flowers.
For me, the powder blue colour of my plant is the "classic" plumbago colour, though I've seen some darker blue varieties which were also very striking. Personally, I'm less keen on white.
One last thing - if you're growing it for the first time, don't panic if nothing seems to be happening in spring. It's deciduous and the new leaves come through very late. When everything else is bursting into life it's still there, brown and dead looking. But it isn't. Stick with it.