Salvia patens is undoubtedly one of the very best blue flowering plants. A native to the temperate and subtropical zones of Mexico, when you consider their late summer/early autumn flowering period there is little else that can compete with the richness of its colour. So good is it that both the species and its cultivar 'Cambridge blue' have gained the Royal Horticultural Society's Award of Garden Merit.
Unfortunately, Salvia patens is frost tender and can only be grown outside in the very warmest regions of northern Europe. This means that it can be a difficult plant to source. However the seed from this gorgeous species is relatively easy to obtain, and as far as I am concerned well worth cultivating.
You will need to provide heat in order to help initiate germination so place the pots or trays into a heated propagator at approximately 18 degrees Celsius.
Do not exclude light as this helps germination, and keep the surface of the compost moist but not waterlogged. The newly germinated seedling should emerge from 14 to 30 days.
Prick out the seedlings once they are large enough to handle and pot on into individual 3 inch pots.
Gradually acclimatise to outdoor conditions for 10-15 days before planting out after all risk of frost had gone. If you are planting in groups, space 18 inches apart.
In the colder areas of northern Europe Salvia patens can only be considered as a half hardy annual, but in the warmer, southern regions it can be grown as a short lived perennial so long as they are planted in sheltered conditions.
It require a warm, sunny position, and to be on the safe side, plant out Salvia patens at the end of May, in ordinary, well-drained garden soil.
Pinch out the growing tips of young plants, once they reach 2-3 inches high, as this will encourage branching.
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