Friday 28 September 2012

Plant of the week

Wonderful black and blue!  

Salvia guaranitica ‘Black and Blue’

Intense blue flowers from September to October 
This is a vigorous herbaceous perennial that is 4ft high in my garden. It is robust and requires no staking. Years ago, a kind friend chopped out a small division for me in July. (Gardeners do not refuse pieces of plant, even if out of season) I now have many fine plants propagated by division in April/May.

Many perennial salvias are tender Mediterranean plants that must have superb drainage. Not this one, my best plants are in wet situations (but not quite boggy). Unusual too, it makes strong tubers, as large as dahlias. Although the plant is sometimes regarded as tender, my strong plants came through the two winters of 2010 without turning a hair. If this is not your own experience, the tubers can be lifted in November, potted and overwintered moist, in a cold greenhouse. Many of us found, to our cost, this was not the best strategy with tender plants in 2010. The cold was so intense and so prolonged that the roots of potted plants were deeply frozen. My tender plants such as agapanthus survived better in the ground.

I have just read that ‘Black and Blue’ can be propagated by cuttings - and seed too. Idiot me, of course most salvias are easy from cuttings! Too late now to try soft tip cuttings, yesterday I rushed out to take a dozen strong, ripened, basal shoots. I inserted them deeply in a single ‘long pot’ in my cold greenhouse. I have no idea whether they will grow!

Salvia guarantica in my gravel garden

 Update November 1st 2014

Four of the aforementioned cuttings rooted. Two did not survive the winter in my unheated greenhouse. This is no surprise as an herbaceous plant that dies down to its winter dormancy soon after rooting has insufficient stored food reserves. The same principle applies to deciduous shrubs rooted late in the growing season when leaf-fall depletes reserves of carbohydrate and they fail to overwinter.

The two salvias that had survived from cutttings made only moderate growth and stayed in their pot for the whole of the next year. They remained in the greenhouse over the following winter before planting out.
The plant from my greenhouse flowered for three months
It would seem to be an advantage to overwinter this salvia in a greenhouse in the north of England as they then flower earlier outside. The plant that had survived from my original cutting and got an early start from the greenhouse flowered from August until November.

In contrast my regular plants in the garden emerge to make new spring growth remarkably late. It's important not to forget they are there! I had almost given them up when they failed to appear until late July!

This plant has been outside for several years and has now been in flower for two months

This one did not appear above ground until the 1st September. Now on the first of November it has very little time to flower. Next year I will move it to a sunnier position. Or perhaps I will lift its tubers that look like those of a dahlia and next spring get lots of new plants from my greenhouse.

I could not resist taking a picture of this monster


  1. Thanks for pointing me in the direction of this post Roger. It's given me food for thought and am just going to have to keep my fingers crossed that they survive. I had not given a thought to the fact that they will die down to the ground. To me, it looks more like a shrub rather than a perennial. This is where my inexperience really kicks in! Being a relatively new introduction, there is contradicting information out there available for Amistad. My cuttings will need to be kept on the kitchen windowsill as I don't have a greenhouse. Again, thanks for this. I've found it extremely useful.

  2. What a coincidence, me alighting on and commenting on your post about Salvia Amistad seconds after I updated this one!
    I can't remember exactly when my cuttings died to the ground in my unheated greenhouse - where the cold probably hastened the event - I guess about December. Yours in the heated house might fair better. The good news was that two from an ordinal dozen cuttings made it!


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