Grace Ward Lithodora, a prostrate groundcover
Lithodora diffusa (formerly Lithospermum diffusum)) is a hardy evergreen creeping groundcover originating in southern Europe & requiring only a little attention. It can hug the ground very closely or mound upward to six inches or rarely as high as a foot. Though there are a handful of cultivars, only 'Grace Ward' is widely distributed.
It spreads as a dark green mat that produces its first few bright azure blue flowers as early as March, but is really going to town blooming in May & June, continuing to bloom at intervals & less overtly up to Autumn's first frost. In our mild Puget Sound weather, it will even produce the occasional bloom, one or two bright blue spots at a time, in any month of the winter.
It likes a little acidity in the soil, but isn't fussy. It likes lots of sun but will tolerate shade. It is very cold-hardy but prefers temperate weather & won't often thrive in American South or Southwest climates. It does not want much moistness & can even survive in droughty conditions under conifers, though blooms will be fewer without sun. It is ideal for rockery ledges, which is where we've planted ours.
Each plant will quickly spread to two feet, & in the longer run could conceivably spread to six feet, though so easily pruned to size there's no risk of it becoming aggressive. When it stops blooming, for the most part in early autumn, that's the time to trim it every other year or so, to keep it from getting too spindly & to encourage regrowth at the center.
Its one fault is that it does get scruffy especially near the center, putting out new growth only around the rim & not always freshening itself at the heart. Its faults are exacerbated by getting too much moisture. The gorgeousness of the blue flowers cannot always make up for the percentage of the plant that leafs poorly & turns black.
I previously had to plant a small "plug" of a new start of lithodora near the center of this one to correct that very problem. It looked much better for quite a long time. The "plug" method obviously crowds the original plant & can't be done repeatedly, so when another part of the spreading lithodora got homely & dead-looking, I decided to remove most of it & hard-prune the rest. The wide area I previously permitted it to cover is now filledby 'Red Fox' Spiked Speedwell (Veronica spicata) with just a bit of lithodora permitted to wend its way about the rockery ledge, peeping out from under the speedwell & Spanish Lavender (Lavandula stoechas). I've found the lithodora a much more satisfactory plant when used as a minor creeper around the bases of perennials.