Salvia × sylvestris 'Crystal Blue' — The Sky-Blue Salvia That Stopped Us in Our Tracks
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There are moments when a plant simply stops you in your tracks. Salvia × sylvestris 'Crystal Blue' is one of those plants — a chance seedling discovered in a nursery field in Michigan, USA, with a flower colour unlike anything else in the genus. Pale, clear sky-blue: not the deep violet-blue of most perennial salvias, but something altogether lighter, fresher, and more unexpected. It had already proven hugely popular in North America before making its UK debut, and it was not hard to see why.
Why It's Special
'Crystal Blue' is part of the Color Spires Series, bred by Jerry VanderKolk and introduced by Walters Gardens and Proven Winners in 2014. It is an early bloomer for a salvia, beginning in late spring and continuing into early summer — and unlike many perennial salvias, it will give a second flush of flower in September if cut back after the first flowering. A long season, a rare colour, and easy to grow: it ticks every box.
- Flower colour: Pale sky-blue — unique in the genus
- Flowering time: July, with a second flush in September if cut back
- Height × Spread: 45cm × 50cm
- Soil: Any reasonable soil with good drainage
- Aspect: Full sun or part shade
- Hardiness: H7 — fully hardy in the UK and across the severest European continental climates
- Awards: RHS Award of Garden Merit (AGM); Runner-up, RHS Chelsea Plant of the Year 2017
A Hardy's Introduction
Hardy's Cottage Garden Plants launched 'Crystal Blue' at the RHS Chelsea Flower Show in 2017 on behalf of the Michigan nursery that first grew it — bringing a plant that had already captivated North American gardeners to a UK audience for the first time. Its Chelsea debut confirmed what growers across the Atlantic already knew: this is a plant of real distinction. The runner-up placing for Plant of the Year at Chelsea 2017 was well deserved.
In the Garden
The pale blue of 'Crystal Blue' is a gift to the border. It sits beautifully alongside whites, silvers, and soft pinks, and provides a cool counterpoint to the warmer tones of late summer planting. Small light blue flowers line upright stems in a classic salvia spike, and the plant holds itself well without staking.
It is a magnet for bees and butterflies throughout its flowering season, making it an excellent choice for pollinator-friendly planting schemes. Whether used in drifts in a mixed border, as part of a prairie-style planting, or massed along a sunny path, 'Crystal Blue' earns its place with ease.
Growing Tips
'Crystal Blue' is straightforward to grow and rewards a little attention with a generous second flush of flower. Cut the stems back as soon as they begin to fade — typically after the main July flowering — and the plant will rebloom in September, extending the season well into autumn.
- Soil: Any reasonable garden soil with good drainage; tolerates some drought once established
- Aspect: Full sun for best flowering; tolerates part shade
- Cutting back: Cut back fading stems promptly to encourage a second flush in September
- Moisture: Regular moisture promotes the best bloom, but the plant is drought-tolerant once established
- Pollinators: Highly attractive to bees and butterflies throughout the season
Frequently Asked Questions
What makes Salvia 'Crystal Blue' different from other perennial salvias?
Its flower colour. Most perennial salvias are deep blue or purple — 'Crystal Blue' is a genuine pale sky-blue, a colour that is rare in the genus and immediately distinctive in the border. It also blooms earlier than many other varieties.
Is Salvia 'Crystal Blue' fully hardy in the UK?
Yes — 'Crystal Blue' is a fully hardy herbaceous perennial, well suited to UK conditions. It is rated H7 on the RHS hardiness scale — hardy in the severest European continental climates (below -20°C) — making it reliably hardy throughout the UK and in exposed positions.
How do I get a second flush of flowers?
Cut the stems back as soon as they start to fade after the main July flowering. This encourages fresh growth and a second flush of bloom in September.
Is Salvia 'Crystal Blue' good for pollinators?
Excellent — it is highly attractive to bees and butterflies throughout its flowering season, making it a valuable addition to any pollinator-friendly garden.
Where was 'Crystal Blue' discovered?
It originated as a chance seedling in a nursery field in Michigan, USA. It was bred by Jerry VanderKolk, introduced by Walters Gardens and Proven Winners in 2014, and launched in the UK by Hardy's Cottage Garden Plants at the RHS Chelsea Flower Show in 2017.
Does Salvia 'Crystal Blue' have any awards?
Yes — it holds the RHS Award of Garden Merit (AGM) and was runner-up for Plant of the Year at the RHS Chelsea Flower Show 2017.