Salvia ‘Mystic Spires Blue’ – A Question of Hardiness

The basics.

Height – 24″-36″.  Spread – 24″ -36″.  Light – full sun.  Bloom color – blue.  Bloom time – June through early fall.  Foliage – rich, leafy, darkish green with blue flower stalks; herbaceous.  Hardiness – zones 7-10.  Growth rate – medium to fast.  Pollinators – bees, butterflies, hummingbirds.

Notes from the field.

As you now know, the Salvia Mystic Spires Blue is not hardy in zones colder than 7.  Use the info here to grow it as an annual in colder zones, or to keep it happy for years to come in zones 7-10.  This hybrid cultivar is a robust grower, but it gets along well with nearby plants.  From the time it began sprouting from its basal stems (approximately mid April in the years before its cold-induced demise), to mid June, my plant put on at least 12″-18″ of growth, and had begun blooming fairly profusely.  And it continued to grow and bloom into late September.  It required virtually no special care at all during the spring, summer, and early fall.

Suggestions for planting Salvia Mystic Spires Blue.

If you get a potted plant from a nursery, plant it as soon as you get it.  If you’re going to grow it as an annual, it makes little sense to try to grow the Salvia Mystic Spires Blue from seed.  In zones 6 or colder, get yourself a healthy, potted specimen (typically available in mid spring in zones 5/6) and get it in the ground as soon as you bring it home, so you can start enjoying its beauty right away.  In warmer zones, you can plant a potted specimen, or you can grow these plants from seed by either direct sowing, or starting them indoors, hardening them off, then planting the viable seedlings.  I’ve read all sorts of different direct sowing recommendations for all sorts of salvias.  Many of those recommendations are contradictory.  I’d suggest following the directions on the seed packet (if that’s the way you end up coming by your seeds).  If you’re planning to start your seeds indoors, a good rule of thumb is to do it 2-3 months before your area’s final frost is expected.

Soil.  My Salvia Mystic Spires Blue grew very well in a slightly acidic (pH of around 6.7 or 6.8), well-drained soil.  My research tells me that these plants can tolerate soil pH levels a few ticks north or south of 7.0.  So neutral, slightly acidic, or slightly alkaline is good.  Mine did great in its slightly-acidic milieu.  The critical soil requirement is good drainage.  These plants will die if their roots stew in soggy, wet, poorly-drained soil.

Water.  These guys don’t need tons of watering to be happy.  Obviously, while they’re establishing, they’ll need more regular watering (one or two semi-heavy soakings per week – if their soil is well-drained like it’s supposed to be – should be enough while they become established).  Once they’re established, however, they’re remarkably drought-tolerant.

Pruning and/or deadheading.  During the blooming season, I cut dead/spent flower stalks down and kept my plant blooming throughout late spring, summer, and early fall.  The plant gets just a little bit sloppy later in the summer and the leaf stems want to flop just a bit.  Although I never cut my Mystic Spires Blue’s leaf stems back at all during the summer, this plant can definitely be pruned back to its basal foliage in order to keep it neater and more compact.  As far as late fall and late winter pruning go, I’ll quote my article of this past March.  This is the methodology I use for all of my salvias:

“Salvias are an herbaceous perennial that love a late winter pruning here in the Midwest.  It’s usually a good idea to leave the dead stems intact (or largely intact – about 12″ of stem) through the fall and coldest months of winter.  This is because salvia stems … are hollow, and pruning a particular plant too close to the ground in the fall could result in freezing moisture within its stems’ hollow centers damaging the plant’s root crown when winter hits its most extreme temperatures.  In late winter, after the danger of extreme, sustained cold has passed, go ahead and prune your salvias down to within a few inches of the root crown.”

Companion planting.  Remember, this plant can get 2′-3′ tall and wide, and it can flop.  Nevertheless, it gets along surprisingly well with nearby plants.  My Salvia Mystic Spires Blue grew beautifully in relatively close proximity to shasta daisies, another salvia cultivar, and iberis.  And as I’ve said, I never had to cut it back in deference to nearby plants.  Although I personally only grew one Mystic Spires Blue, I often imagined what a drift of several of them might look like.  Those blue flowers are amazing, and I believe that a whole mess of them inking up the landscape would be a sight to behold.