Snow in Summer
Easy to grow. A ground covering plant, but not invasive (well, not in my garden). The prettiest white flowers on clean silver foliage, with the tiniest leaves. This is Cerastium Tomentosum (Snow in Summer).
Snow in Summer is as delightful as its extremely creative pet name suggests. But it's oh so easily pulled out when one is vigorously weeding at the wrong time of year. Oops! Careful!
I'm usually very wary of ground covers, having had a few creeping disasters. Looking up Cerastium Tomentosum in some local nursery websites, I found the following adjectives : 'very hardy', 'vigorous' and 'easy to grow', which might start alarm bells ringing. But this perennial has never behaved badly in my garden.
Here's Wikipedia's paragraph on Cerastium Tomentosum : 'Cerastium tomentosum is an herbaceous flowering plant and a member of the family Caryophyllaceae. It is generally distinguished from other species of its genus by 'tomentose' or felty foliage. It is a low, spreading perennial native to alpine regions of Europe.'