Brunnera macrophylla ‘Jack Frost’: A jewel for the shade garden

In the realm of shade-loving perennials, few plants capture the imagination quite like Brunnera macrophylla ‘Jack Frost’.

With its striking silver foliage veined with green and delicate blue flowers, this award-winning cultivar has become a favourite among gardeners seeking to brighten shadowy corners of their landscapes.

‘Jack Frost’ offers months of visual interest with minimal maintenance, making it an excellent choice for both novice and experienced gardeners alike.

Featured Image: Brunnera macrophylla ‘Jack Frost’ by Krzysztof Ziarnek, Kenraiz is licensed under CC BY-SA 4.0

The Exciting ‘Jack Frost’

Brunnera macrophylla, commonly known as Siberian bugloss or false forget-me-not, is a woodland perennial native to Eastern Europe and Western Asia. The cultivar ‘Jack Frost’, introduced in the early 2000s, quickly rose to prominence, earning the prestigious Perennial Plant of the Year award in 2012 from the Perennial Plant Association.

What sets ‘Jack Frost’ apart from the standard species is its remarkable foliage. The heart-shaped leaves feature a stunning silver overlay with intricate green veining, creating a frosted, metallic appearance that seemingly glows in shaded areas.

This silver patterning is due to a unique genetic characteristic that reduces chlorophyll between the leaf veins, allowing the silvery colour to dominate.

In spring, the plant produces sprays of tiny, bright blue flowers that closely resemble forget-me-nots, hovering above the foliage on slender stems (see image further below). This delightful combination of silvery leaves and sea-blue flowers creates a magical effect in the garden from April through June.

Growing Conditions: What ‘Jack Frost’ Needs to Thrive

Light Requirements

Despite its light appearance, ‘Jack Frost’ is not fond of intense sunlight. It performs best in partial to full shade, making it ideal for woodland gardens, north-facing borders, or areas beneath deciduous trees.

Morning sun with afternoon shade provides an optimal balance for this plant, as too much direct sunlight can scorch the delicate foliage, causing the silver colouration to fade.

Soil Preferences

Brunnera ‘Jack Frost’ prefers rich, consistently moist, well-draining soil with high organic content. A soil pH that is slightly acidic to neutral (6.0-7.0) is ideal. Before planting, amend garden soil with compost or well-rotted leaf mold to improve both drainage and moisture retention.

Water Needs

Regular watering is essential, especially during establishment and dry periods. ‘Jack Frost’ appreciates consistent moisture but can’t take waterlogged conditions, which can lead to root rot. A 2-3 inch layer of organic mulch helps maintain soil moisture and suppresses weeds, which can compete with the relatively shallow-rooted Brunnera.

Temperature and Hardiness

This perennial is quite hardy, thriving in USDA zones 3-8. It withstands cold winters admirably but may struggle in areas with hot, humid summers. In warmer regions (zones 7-8), providing deeper shade and consistent moisture becomes especially important to help the plant cope with higher temperatures.

Planting and Care Tips

Planting Time and Method

Early spring or early fall/autumn are ideal times to plant Brunnera ‘Jack Frost’. Space plants 12-18 inches (30-45cm) apart to allow for their eventual spread. When planting, position the crown at the same level as it was in its pot, taking care not to bury it too deeply.

Fertilization

‘Jack Frost’ is not a heavy feeder. A light application of balanced, slow-release fertiliser in early spring is typically sufficient. Alternatively, top-dress with compost annually to provide nutrients while improving soil structure.

Division and Maintenance

Divide established plants every 3-4 years to maintain vigour and prevent overcrowding. The best time for division is early spring, just as new growth emerges. Gently separate the clumps, ensuring each division has both roots and shoots, and replant immediately.

Remove spent flower stems after blooming to maintain a tidy appearance. In late winter, trim away any tattered or damaged foliage before new growth emerges. During particularly hot summers, the foliage may decline; trimming back affected leaves encourages fresh growth as temperatures cool.

Pest and Disease Management

Brunnera ‘Jack Frost’ is relatively trouble-free, but it can occasionally suffer from slug and snail damage. Regular monitoring and appropriate control measures, such as diatomaceous earth barriers or hand-picking, help manage these pests.

Crown rot can occur in poorly draining soils or excessively wet conditions. Ensure proper spacing between plants to improve air circulation and avoid overhead watering, particularly in humid climates.

Companion Planting: Creating Harmonious Combinations

The silvery foliage of ‘Jack Frost’ creates a luminous effect in shaded areas, making it an excellent companion for plants with contrasting colours and textures. Consider these harmonious pairings:

• Ferns: The delicate fronds of Japanese painted ferns (Athyrium niponicum ‘Pictum’) or autumn ferns (Dryopteris erythrosora) complement the broad leaves of Brunnera.
• Hostas: Varieties with blue-green or deep green foliage provide an excellent contrast to the silvery ‘Jack Frost’.
• Bleeding Hearts: Dicentra spectabilis blooms concurrently with Brunnera, creating a charming spring display.
• Heucheras: Purple-leaved varieties like ‘Palace Purple’ or ‘Obsidian’ create dramatic contrasts against the silver Brunnera foliage.
• Spring Bulbs: Combine with early blooming bulbs like snowdrops, crocuses, or daffodils for extended seasonal interest.

Design Applications in the Garden

Jack Frost’ Brunnera serves multiple purposes in garden design:

• Brightening Shade: The silver foliage illuminates dark corners of the garden, creating focal points in otherwise somber areas.
• Woodland Gardens: Its natural habitat makes it perfect for naturalistic woodland settings.
• Border Edges: The compact habit (12-15 inches tall and 18-24 inches wide) makes it suitable for the front or middle of shaded borders.
• Container Planting: ‘Jack Frost’ performs well in containers, particularly in shadier patios or porches.
• Ground Cover: When planted en masse, it creates a stunning silver carpet beneath trees or shrubs.

Seasonal Interest

While ‘Jack Frost’ is primarily known for its spring display, it offers garden interest throughout much of the growing season:

• Early Spring: Fresh silver foliage emerges, creating immediate impact.
• Mid-Spring to Early Summer: Blue flowers appear, attracting early pollinators.
• Summer: The foliage continues to provide a cooling visual effect, even as flowers fade.
• Fall: Though it begins to decline with the approach of dormancy, the silvery leaves often persist until frost.

Final Thoughts

Brunnera macrophylla ‘Jack Frost’ represents a great balance of beauty and practicality. Its stunning appearance, adaptability to challenging shaded conditions, and relatively low maintenance requirements make it a valuable addition to any garden.

For those seeking to bring light and texture to their shadowy garden spaces, this silver-leaved perennial offers a terrific solution. With proper care, Brunnera ‘Jack Frost’ will return year after year, its heart-shaped leaves and forget-me-not flowers becoming old friends in the ever-evolving story of your garden.