One of the faults that plagues rosemaries is their default desaturated grey-blue flowers. This can look fabulous when working with a very restrained dry-plant palette, but can just look plain dowdy in a more colourful garden setting.
Enter Rosemary ‘Blue Lagoon’. Its flowers, that continue for months throughout winter into spring, are brilliantly blue. It attracts bees and both nectar- and insect-eating birds. It thrives with absolutely no water, as long as drainage is good. It smells delicious every time you brush past it, and you can sprinkle the leaves on roast potatoes or a leg of lamb.
It’s sold as a ground cover, or as semi-prostrate. I’d love it more if it was truly prostrate. Unfortunately the most prostrate of all forms of rosemary, that drape extravagantly over walls like strings of heavy beads, are all depressingly grey-blue in flower. And I’d probably love it more if it was truly, emphatically upright, like Salvia rosmarinus ‘Tuscan Blue’ (whose flowers, as good as they are, look seriously diluted compared to ‘Blue Lagoon’). As it happens, it’s slightly annoyingly in between. Rosemary ‘Blue Lagoon’ is low and spreading in form, and relatively ground hugging, but it can eventually mound itself up, in its centre, to a rather hollow 1m. The best flowering is always on the younger growth around the edges.
It’s truly fabulous spilling over a retaining wall (from which it also benefits from the drainage that that setting always provides), or down the sides of stairs, but you really need room for it. I planted one either side of a smallish set of sleeper stairs at my place, and one of those plants now covers an area 3m long and 2m wide. I’d actually written that it covers 2 sq metres, then thought I’d better go and verify. It actually covers 6 sq metres! The only way to keep it smaller is to prune it very hard indeed, and preferably every year, just as the flowers start to fade. A plant allowed to grow unchecked is much less tolerant of an occasional very hard pruning than one hard-pruned regularly, largely due to the age of the wood that you’re cutting back into, and expecting to reshoot.
Having said that, I hacked one of my plants back to stumps a couple of years ago, (in order to re-find the stairs!) and a great deal of it never reshot. A single branch or two did reshoot, and have subsequently taken the place of the original.
I’ve mentioned drainage a couple of times, but need to do so again. The natural terrain of these plants is very open, very poor (nutritionally), and perfectly drained stoney soil. The more you can replicate these conditions, the longer your rosemarys will last. In well fed and well watered conditions, they’ll grow fast and fat, then die young, of the plant equivalent of obesity.
But keep then well-drained and at least slightly underfed, pruning hard every spring, and you’ll get many years of taste-, smell- and sight-pleasure from them. And the birds and bees will love you too.