Brunnera ‘Silver Heart’ vs ‘Jack Frost’ – How Do These Popular Varieties Compare?

Brunnera also known as Siberian bugloss, has become a popular shade loving perennial in many gardens. Two of the most widely grown Brunnera varieties are ‘Silver Heart’ and ‘Jack Frost’. While quite similar these two varieties have some key differences that gardeners should understand when making their selection. In this article, we will compare and contrast Brunnera ‘Silver Heart’ and ‘Jack Frost’ to help you choose the best variety for your landscape.

Background on Brunnera Varieties

Native to the Caucus region Brunnera is valued for its clusters of small blue flowers in spring and its large, heart-shaped leaves that remain attractive all season. The plant thrives in shade and spreads slowly to form a lush groundcover.

There are over a dozen unique Brunnera cultivars available, featuring leaf colors like silver, green, and variegated The two most popular varieties are Brunnera macrophylla ‘Jack Frost’ and ‘Silver Heart’ Let’s explore how these two compare.

Growth Habit and Size

Both ‘Jack Frost’ and ‘Silver Heart’ grow in a clump form, with a mounded habit and heart-shaped leaves on long stems. However, there are some differences in their size and growth habits:

• ‘Jack Frost’ grows 12-15 inches tall and spreads 15-18 inches wide. It has a compact, mound-shaped habit.

• ‘Silver Heart’ is slightly larger, reaching 15-20 inches tall and 18-24 inches wide. It features a more open, vase-shaped growth habit.

So ‘Silver Heart’ ultimately grows a little bit taller and wider than ‘Jack Frost’. Both spread slowly via rhizomatous roots to form thick clumps.

Foliage Appearance

The most noticeable difference between these two Brunnera varieties is the leaf color and patterning:

• ‘Jack Frost’ has silver leaves with pronounced green veining. The bold contrast between the silver and green has a dramatic frosted or crackled effect.

• ‘Silver Heart’ also has silver leaves but the green veining is more subtle. The overall look of the foliage is more solid silver rather than frosted.

In both varieties, the leaves have a hairy, textured appearance. ‘Jack Frost’ leaves tend to be more deeply cut and pointed while ‘Silver Heart’ leaves are broader with rounded tips. The foliage remains attractive throughout the season with the silver color acting as a great foliage “neutral”.

Flowers

Both ‘Silver Heart’ and ‘Jack Frost’ produce small clusters of baby blue flowers in spring, typically during April or May. The flowers have five petals and rise above the foliage on thin stems.

There is little difference between the blooms of these two Brunnera varieties – they both feature abundant dainty blue blossoms that nicely complement the silver foliage. Some gardeners remove the flower stems after blooming to prevent self-seeding.

Growing Conditions

As with most Brunnera varieties, both ‘Silver Heart’ and ‘Jack Frost’ require similar growing conditions:

• Light: Partial to full shade is ideal, with some tolerance for morning sun. Afternoon sun will scorch the leaves.

• Soil: Moist, humus-rich soil with good drainage. Avoid dry, sandy sites.

• Zone: Hardy in zones 3-8. Often winter hardy even in zone 2.

• Water: Keep soil moist but not saturated. Reduce watering once established.

Neither variety is picky about soil pH, though acidic to neutral is preferred. While drought tolerant once established, both need adequate moisture when first planted. Mulching helps maintain soil moisture and temperature.

Landscape Uses

The frosted silver leaves of ‘Jack Frost’ make it a popular choice to brighten shaded garden beds, borders, woodland gardens, and container plantings. It combines well with ferns, hostas, astilbes, and other shade lovers.

‘Silver Heart’ also works nicely in shade gardens, borders, and patio containers. Its more subtle silver leaves complement other plants without drawing too much attention to itself. It mixes well in large combination planters.

Both varieties work great as groundcovers and edging plants. They spread slowly to form attractive masses and help suppress weeds. Their low mounded habit also makes them effective in smaller-scale applications like rock gardens.

Care and Maintenance

Brunnera requires minimal care once established:

• Water during droughts the first year. After established, it is quite drought tolerant.

• Remove spent flower stems to control self-seeding. Cut back leggy growth in late spring.

• Cut plants back to the ground in late fall prior to winter.

• Divide congested clumps every 2-3 years in early spring.

• Watch for slugs and snails, powdery mildew, and crown rot. Excellent pest and disease resistance overall.

• Apply fertilizer, compost, or mulch in spring to boost growth. Avoid high nitrogen products.

Both ‘Silver Heart’ and ‘Jack Frost’ have minimal maintenance needs once settled in. They are not prone to serious pest or disease issues. Divide when the clumps get overcrowded to maintain vigor.

Key Differences Summary

While quite similar, here are some key differences between Brunnera ‘Silver Heart’ and ‘Jack Frost’ at a glance:

• ‘Silver Heart’ has more subtle silver leaves and a slightly larger, more open habit.

• ‘Jack Frost’ features bold frosted silver leaves and a compact mounded form.

• ‘Silver Heart’ foliage is primarily solid silver vs the veined look of ‘Jack Frost’.

• Both have small blue spring flowers and require similar growing conditions.

• ‘Silver Heart’ works well in combinations where foliage contrast is not desired.

• ‘Jack Frost’ makes a more dramatic statement and complements bolder plantings.

Other Notable Brunnera Varieties

While ‘Silver Heart’ and ‘Jack Frost’ are the most popular choices, here are a few other excellent Brunnera varieties to consider:

• ‘Looking Glass’ – Completely silver metallic looking leaves. More heat tolerant.

• ‘Sea Heart’ – Silver leaves with dark green veining. Leaves are heart-shaped.

• ‘Alexander’s Great’ – Large green leaves with silver accents. Grows up to 30 inches tall.

• ‘Mr. Morse’ – Variegated green and creamy white leaves with yellow flowers in spring.

• ‘Emerald Mist’ – Green leaves that emerge bright red in spring. Compact at 12″ tall.

There are also dwarf Brunnera varieties like ‘Baby Tutu’ and ‘Little Joe’ that only reach 6 inches tall – perfect for trough gardens and containers.

With many wonderful varieties to choose from, Brunnera can add striking foliar effects to shaded plantings. Be sure to select the variety that best suits your specific needs and design goals. Proper planting and care will reward you with years of beauty.