Liquorice Blue Korean Mint (Korean Hyssop) care

Light

Aim for at least 4-6 hours of direct sun on the leaves. Needs at least 6 hours of direct sun daily for best flowering and oil production. In hot climates, light afternoon shade is tolerated but reduces bloom density. Leggy growth and poor fragrance result from insufficient light. If your only bright window faces south, that's perfect for liquorice blue korean mint — same window any aroid would fry on.

Watering

Watering liquorice blue korean mint: every 5–7 days; reduce in winter. The number that matters isn't the day of the week — it's how dry the top 2-3 cm of the pot feels. A finger in the soil tells you more than a watering app. After every watering, tip the saucer. Water deeply when the top 5 cm of soil feels dry. Established plants are drought-tolerant; overwatering or wet feet causes root rot. Avoid waterlogging, especially in heavy clay soils.

Soil and pot

Liquorice Blue Korean Mint grows best in well-drained loam or sandy loam, ph 6.0–7.5. Prefers lean to moderately fertile, free-draining soil. Overly rich or waterlogged soil promotes lush but floppy growth and reduces aromatic oil content. Amend clay soils with grit or coarse sand. 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

Liquorice Blue Korean Mint sits happiest at around 30–60% humidity and −15°C to 35°C (5°F to 95°F). Tolerates typical outdoor humidity without issue. Good air circulation is more important than humidity level — stagnant, humid conditions encourage powdery mildew on foliage. If you keep the room above −15°C to 35°C 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 liquorice blue korean mint sparingly. Apply a balanced, low-nitrogen fertiliser (e.g., 5-10-10) once in early spring. Excess nitrogen encourages leafy growth at the expense of flowers. In poor soils, a second light feed in early summer is acceptable. 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 liquorice blue korean mint in the Growli community. Each is annotated with the most common cause so you know where to start.

• Powdery mildew — Common in humid, poorly ventilated spots. Improve air circulation, avoid overhead watering, and remove affected stems. Resistant cultivars like 'Liquorice Blue' are less susceptible but not immune.
• Root rot from overwatering — Plants wilt and decline if roots sit in wet soil. Ensure sharp drainage and allow the top layer of soil to dry between waterings. Most fatal in heavy clay or compacted soil.
• Flopping / legginess — Results from too much shade or overfeeding with nitrogen. Cut back by one-third after the first flush of flowers to encourage compact regrowth and a second bloom.

Propagation

Sow seed indoors 6–8 weeks before last frost (surface-sow, needs light to germinate at 18–21°C). Divide established clumps in spring. Stem cuttings taken in early summer root readily in moist perlite. 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

Liquorice Blue Korean Mint is pet-safe. Agastache rugosa is not listed as toxic by the ASPCA. The genus belongs to Lamiaceae (mint family), which has no reported systemic toxic principles in pets. Culinary use by humans is established. Exercise normal caution with large ingestions. 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.

Liquorice Blue Korean Mint deep-dive guides

Every aspect of liquorice blue korean mint care, each with its own calibrated guide:

• Common liquorice blue korean mint problems & fixes
• Liquorice Blue Korean Mint watering schedule
• Liquorice Blue Korean Mint light requirements
• Best soil mix for liquorice blue korean mint
• Liquorice Blue Korean Mint fertilizing guide
• When to repot liquorice blue korean mint
• How to propagate liquorice blue korean mint
• How to prune liquorice blue korean mint
• What's eating my liquorice blue korean mint?
• Liquorice Blue Korean Mint growth rate & size
• Liquorice Blue Korean Mint cold hardiness
• Liquorice Blue Korean Mint temperature & humidity
• Is liquorice blue korean mint toxic to cats & dogs?
• Is liquorice blue korean mint toxic to cats?
• Is liquorice blue korean mint toxic to dogs?
• All 17 Agastache varieties

Featured in these plant shortlists

Liquorice Blue Korean Mint qualifies for 2 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

• Best pet-safe low-maintenance plants — Non-toxic to cats and dogs and forgiving of forgotten watering — the easiest safe choices for a busy pet household.
• Best fragrant houseplants — Indoor plants with scented flowers or aromatic foliage — greenery you can smell, selected from our care library.
• Browse all 29 plant shortlists — pet-safe, low-light, drought-tolerant and more

Related guides

Liquorice Blue Korean Mint is also known as Liquorice Blue Korean Mint, Korean Hyssop, Blue Licorice Mint, and Wrinkled Giant Hyssop.

• Hart's Pennyroyal care — light, water and common problems
• Gattefosse's Mint care — light, water and common problems
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• All 8452 plant care guides in the Growli library