Brunnera macrophylla 'Jack Frost' (Jack Frost Siberian bugloss) care

Light

Picture the indirect light an east-facing window gives mid-morning — that's the brightness brunnera macrophylla 'jack frost' grows fastest in. Partial to full shade. The silvered leaves can take some morning sun in cool climates, but hot afternoon sun scorches the foliage and browns the leaf edges. Deeper shade keeps the frosting crisp. You'll know it's right when new leaves come out the same size and colour as the established ones. Smaller, paler new leaves = move closer to the window.

Watering

Aim for when the top 2-3 cm of soil is dry, roughly every 5-7 days for brunnera macrophylla 'jack frost', but treat that as a starting point rather than a rule. A south-facing summer windowsill will dry the pot twice as fast as a north-facing winter room. Lift the pot; if it feels noticeably lighter than it did wet, water it. Keep soil consistently moist, especially in its first season and during dry spells. Established plants tolerate brief dryness but wilt and crisp at the edges if too dry. Mulch to retain moisture.

Soil and pot

Brunnera macrophylla 'Jack Frost' grows best in moist, well-drained, humus-rich soil. Fertile, organically rich soil that stays moist but drains freely. Tolerant of a range of pH. Amend with compost or leaf mould; avoid bone-dry or compacted soil, which causes leaf scorch. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Brunnera macrophylla 'Jack Frost' sits happiest at around Ambient outdoor humidity and -1 to 24°C active growth (hardy to about -40°C dormant) (30 to 75°F active growth (hardy to about -40°F dormant)). A hardy outdoor perennial with no special humidity needs. Cool, moist woodland conditions suit it best; soil moisture is more important than air humidity. If you keep the room above year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed brunnera macrophylla 'jack frost' sparingly. Minimal feeder. A spring top-dressing of compost or a single application of balanced slow-release fertiliser is plenty. Over-feeding is unnecessary and offers no benefit to this tough groundcover. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on brunnera macrophylla 'jack frost' in the Growli community. Each is annotated with the most common cause so you know where to start.

• Leaf scorch — Too much sun or dry soil browns and crisps leaf margins. Move to deeper shade and keep soil moist; cut back damaged leaves to force fresh growth.
• Loss of silver frosting — In deep shade or poor light the metallic effect can dull. Bright, indirect woodland light keeps the frosting at its best without scorching.
• Slug and snail grazing — Young leaves in damp shade attract slugs and snails. Use barriers or wildlife-safe controls.
• Crown rot in wet soil — Waterlogged winter soil can rot the crown. Plant in humus-rich, free-draining ground.

Propagation

Divide clumps in early spring or autumn. Note that variegated 'Jack Frost' is a cultivar best propagated by division or root cuttings, not seed — seedlings revert to plain green. Replant divisions into moist, enriched soil. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Brunnera macrophylla 'Jack Frost' is mildly toxic to pets. Brunnera macrophylla is not individually listed in the ASPCA Toxic/Non-Toxic Plants database, so its status is not confirmed. As a member of the borage family (Boraginaceae) it can contain low levels of pyrrolizidine alkaloids. Treat with caution and verify with a vet if a pet ingests it; do not assume it is pet-safe. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Brunnera macrophylla 'Jack Frost' deep-dive guides

Every aspect of brunnera macrophylla 'jack frost' care, each with its own calibrated guide:

• Brunnera macrophylla 'Jack Frost' watering schedule
• Brunnera macrophylla 'Jack Frost' light requirements
• Best soil mix for brunnera macrophylla 'jack frost'
• Brunnera macrophylla 'Jack Frost' fertilizing guide
• When to repot brunnera macrophylla 'jack frost'
• How to propagate brunnera macrophylla 'jack frost'
• Brunnera macrophylla 'Jack Frost' growth rate & size
• Brunnera macrophylla 'Jack Frost' cold hardiness
• Brunnera macrophylla 'Jack Frost' temperature & humidity
• Is brunnera macrophylla 'jack frost' toxic to cats & dogs?
• Is brunnera macrophylla 'jack frost' toxic to cats?
• Is brunnera macrophylla 'jack frost' toxic to dogs?
• Getting brunnera macrophylla 'jack frost' to bloom

Featured in these plant shortlists

Brunnera macrophylla 'Jack Frost' qualifies for 4 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

• Best low-light houseplants — Houseplants that need no direct sun and cope with a north-facing room or a spot well back from a window.
• Best plants for a north-facing window — Houseplants for a north-facing window: bright, even, indirect light and no scorching direct sun. Each pick verified against its documented light needs.
• Best flowering houseplants — Indoor plants grown for their blooms — selected from the flowering species in Growli’s plant-care library.
• Best houseplants for a cool room — Houseplants that tolerate cool conditions down to about 10°C — for an unheated spare room, hallway, porch or a home kept cool.
• Browse all 29 plant shortlists — pet-safe, low-light, drought-tolerant and more

Related guides

Brunnera macrophylla 'Jack Frost' is also commonly called Jack Frost Siberian bugloss or Jack Frost brunnera.

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