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Plant care

Mountain Lemon Thyme (Pyrenean thyme) care

Thymus nervosus

Also called Mountain lemon thyme, Pyrenean thyme.

RHS H5USDA 5-9Pet-safeIndoor 10–15 cm tall

Watering rhythm

Direct sun (at least 4-6 hours)

Low — water sparingly; drought-tolerant once established

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Light

Direct sun (at least 4-6 hours)

Soil

Sharply drained, gritty, alkaline to neutral soil

Humidity

Low to moderate — prefers dry, open conditions

Temp

-20 to 28°C

Pet safety

Pet-safe

Mature size

10–15 cm tall

Care at a glance

Light

Mountain Lemon Thyme needs sun on the leaves, not just bright ambient room light. Needs full sun for at least 6 hours daily; its native mountain habitat is fully exposed south- or south-west-facing scree and short turf. A south or west-facing windowsill in the northern hemisphere is the default; anywhere else, expect the plant to stretch and pale out within a season.

Watering

Water mountain lemon thyme low — water sparingly; drought-tolerant once established. The actual day count varies with pot size, light, and season — the finger test (or lifting the pot to feel its weight) is more reliable than a fixed calendar. Empty any drainage saucer afterwards so the pot isn't sitting in water. Allows the root zone to dry completely between waterings; in the UK, established plants rarely need supplemental irrigation. Winter wet at the crown is the main threat, not cold.

Soil and pot

Mountain Lemon Thyme grows best in sharply drained, gritty, alkaline to neutral soil. Incorporate generous horticultural grit or gravel; a 5 cm grit mulch around the collar of the plant is recommended in high-rainfall sites to keep the crown dry. 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

Mountain Lemon Thyme sits happiest at around Low to moderate — prefers dry, open conditions humidity and -20 to 28°C (-4 to 82°F). In humid or overcast climates, prioritise good air circulation and avoid planting in sheltered corners where moisture accumulates. 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 mountain lemon thyme sparingly. Fertilise minimally — a light dressing of a slow-release, low-nitrogen feed once in early spring keeps growth compact and aromatic; heavy feeding reduces essential-oil concentration and promotes soft growth. 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 mountain lemon thyme in the Growli community. Each is annotated with the most common cause so you know where to start.

  • Winter crown rot — High rainfall combined with poor drainage causes the crown and lower stems to rot over winter. A grit collar around the base and a south-facing aspect are the most effective preventive measures.
  • Woody die-back — Without annual post-flowering trimming the centre becomes bare wood that will not regenerate. Clip back by up to one-third after flowers fade, cutting into green wood only.

Propagation

Take 5–8 cm semi-ripe cuttings from non-flowering lateral shoots in early to mid summer and root in a gritty, free-draining medium. Division of clumps in spring is simple and reliable. Seed can be sown under glass in late winter but viability and germination rates vary. 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

Mountain Lemon Thyme is pet-safe. ASPCA lists Thymus species as non-toxic to dogs, cats, and horses. The whole garden plant carries no toxic principles; concentrated thyme essential oil is a separate product and should not be used on pets. 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.

Mountain Lemon Thyme care — frequently asked questions

What is the common name for Thymus nervosus?

Thymus nervosus is most commonly called Mountain Lemon Thyme, but it is also known as Mountain lemon thyme, Pyrenean thyme. The names refer to the same species, so care instructions for Mountain Lemon Thyme apply identically to anything sold as Pyrenean thyme.

How much light does mountain lemon thyme need?

Mountain Lemon Thyme grows best in direct sun (at least 4-6 hours). Needs full sun for at least 6 hours daily; its native mountain habitat is fully exposed south- or south-west-facing scree and short turf.

How often should I water mountain lemon thyme?

Water mountain lemon thyme low — water sparingly; drought-tolerant once established. Allows the root zone to dry completely between waterings; in the UK, established plants rarely need supplemental irrigation. Winter wet at the crown is the main threat, not cold. The finger-test (or lifting the pot to feel its weight) beats a fixed weekly calendar because pot size, light, and season all change how fast the soil dries.

Is mountain lemon thyme toxic to cats and dogs?

Mountain Lemon Thyme is pet-safe. ASPCA lists Thymus species as non-toxic to dogs, cats, and horses. The whole garden plant carries no toxic principles; concentrated thyme essential oil is a separate product and should not be used on pets.

What USDA hardiness zone does mountain lemon thyme grow in?

Mountain Lemon Thyme is rated for USDA zone 5-9 and RHS hardiness H5. Outside that range, grow it as a container plant that overwinters indoors before the first hard frost.

Mountain Lemon Thyme deep-dive guides

Every aspect of mountain lemon thyme care, each with its own calibrated guide:

Featured in these plant shortlists

Mountain Lemon Thyme qualifies for 2 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

Related guides

Mountain Lemon Thyme is also commonly called Mountain lemon thyme or Pyrenean thyme.