PLANT OF THE WEEK #73: Rosemary 'Blue Lagoon' (Salvia rosmarinus 'Blue Lagoon')

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.  

Lily flowered tulips against Rosemary ‘Blue Lagoon’

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. 

Plant on the left not cut back for years (it’s more than double the size of what you can see here). Plant on the right hacked right back to stumps, with not a green leaf showing, a couple of years back

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.

I’d love Rosemary ‘Blue Lagoon’ a little more if it was capable of this. The above is an unnamed form of emphatically prostrate rosemary at The Paul Getty Centre in LA, overhung with wonderfully skeletal specimens of our own coastal tea tree. We really need someone to breed the colour of ‘Blue Lagoon’ into a plant of this fabulous form.


  1. I have “Mozart”, which is also an intense blue. I love it in winter with bright orange Calendulas that self-seed around it.

    1. I must grow one myself, to compare. I’ve just planted many of them in a friend’s garden, and they appeared to me (without other forms for comparison) to be closer to ‘Tuscan Blue’. But I remember clearly the first time I saw T Blue, and thought it the most intense colour. Now I’ve grown it for years, and never have that same conviction

  2. Of all plants in our Mediterranean climate garden, Rosemary ‘Blue Lagoon’ holds the highest utility status and therefore probably our most repeat-planted staple.

    Originally given to me as cuttings from a gardening friend 25 years ago, ‘Blue Lagoon’ was integral to providing new garden structure in a paddock as a very long 500mm high hedge, now mostly all removed except for a few hangers-on. As you say, good drainage is important to the plant’s success – our greatest losses of this plant occurred in the wettest seasons. Tough love with low irrigation and poor sandy soil is why some have lasted so long.

    Not sure if the tough love results in a higher aromatic oil concentration in it’s foliage, but I’ve rendered a Potato Pizza almost inedible with ‘Blue Lagoon’ and vowed to only use ‘Tuscan Blue’ for cooking n future!

    ‘Blue Lagoon’, in my experience, has been the easiest of all the Rosemaries to strike and will lay rootlets into mulch over damper months, providing a new crop of plants to share.

    Frequently attempting to channel Nicole de Vésian, ‘Blue Lagoon’ is clipped into tight roundish and cloud shapes to accentuate each plant own identity in our garden. It quickly fill gaps and looks especially good alongside a contrasty foliage planting such as Agapanthus straps, wispy silver Artemisia or bold rosettes of Aeonium.

    In recent years, ‘pants’ plantings of ‘Blue Lagoon’ around the base of young Olives has minimised so much Rabbit ringbark damage we’ve had in the past.
    I’ve even had a measure of success in achieving a drapey effect with ‘Blue Lagoon’ over stone walls; it requires some serious OCD clipping 2-3 times a year to maintain a more veil-type swathe … worth the effort though if you’re a bit of an Edward Scissorhands anyway.

    Such an indispensable plant for our garden.

    1. I love this, Jenni – all the pros and cons (and as we know, all plants have both, despite what hyperbolic nursery labels, mag articles, or the occasional discernment-light Plant of the Week might say).

      I understand that the tough love does result in higher aromatic oil concentration, but I guess that leads to the question of why your ‘Tuscan Blue’ isn’t likewise super-flavoured. Having said that I once met a guy who grew more than thirty different rosemaries commercially for oil extraction, and was able to explain to me how much variation there is. I wish I’d had a chance to see them all in bloom. There must be some fabulous forms out there that should be in gardens.

      So interested that you clip it. I would have thought that all new growth was just too lax to make that worthwhile.

      And that ‘pants’ planting idea is a cracker! Do you think the rosemary repels the rabbits, or distracts them by giving them something better to eat, or just keeps them physically at bay?

    2. Why on earth would I never have asked myself this really obvious question re why tough love applied to both ‘Tuscan Blue’ and ‘Blue Lagoon’ resulted in a singular type of bad pizza experience?

      Did some rabbit-holing and it appears the R. officinalis var. albiflorus (French type) and R. officinalis var. Gorizia (Italian type) have an ‘enormous variation of volatile components’. Apparently one type of foliage is more needle-like and the other flatter. I wouldn’t think ‘Blue Lagoon’ is really that needle-like but ‘Tuscan Blue certainly has larger and flatter leaves.

      Re clipping: new growth in our climate is only lax if grown in part shade, it’s a ripper clipper. The ‘pants’ planting achieves all of what you suggest, depending on season. Rabbits here would rather dig up and eat the roots of Rosemary than the plant’s foliage in March/April when there’s little else on offer.

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