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Plant care

Cosson's Germander (Balearic germander) care

Teucrium cossonii

Also called Cosson's germander, Balearic germander.

RHS H4USDA 7-10Mildly toxic to petsIndoor 5–15 cm tall and 30–60 cm wide.

Watering rhythm

2-3weeks

Sparingly every 2–3 weeks in summer; minimal to none in winter

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Light

Direct sun (at least 4-6 hours)

Soil

Extremely free-draining, poor, calcareous or neutral

Humidity

Low (25–45% RH)

Temp

-8 to 35°C

Pet safety

Mildly toxic to pets

Mature size

5–15 cm tall and 30–60 cm wide.

Care at a glance

Light

Aim for at least 4-6 hours of direct sun on the leaves. Requires maximum sun to flower prolifically and maintain the characteristic silver felting; in shade the plant etiolates and loses its neat prostrate habit. If your only bright window faces south, that's perfect for cosson's germander — same window any aroid would fry on.

Watering

Watering cosson's germander: sparingly every 2–3 weeks in summer; minimal to none 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. Exceptionally drought-tolerant in free-draining soil; the woolly grey foliage reflects heat and reduces water loss. Any standing winter moisture around the crown is fatal.

Soil and pot

Cosson's Germander grows best in extremely free-draining, poor, calcareous or neutral. Best in a gritty scree mix (2 parts coarse grit : 1 part loam : 1 part peat substitute) or wedged into the crevices of a dry stone wall; never plant in clay or moisture-retentive soil. 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

Cosson's Germander sits happiest at around Low (25–45% RH) humidity and -8 to 35°C (18 to 95°F). A coastal Mediterranean endemic accustomed to dry, sun-drenched conditions; prolonged wet, cool weather, particularly in winter, quickly rots the stems and root crown. 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 cosson's germander sparingly. No regular feeding; a single very light application of slow-release fertiliser in spring is the maximum — rich conditions destroy the silver compact habit and encourage disease. 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 cosson's germander in the Growli community. Each is annotated with the most common cause so you know where to start.

  • Root rot in winter wet — The primary cause of losses in UK and PNW gardens; even short periods of waterlogging during cold weather rot the fine roots and crown. Grow in raised scree beds or against a dry, south-facing wall.
  • Stem dieback from frost combined with moisture — Frost alone is usually tolerated, but frost on wet stems causes dieback; protect with a grit mulch around the crown and ensure overhead shelter in particularly cold, wet winters.

Propagation

Semi-ripe cuttings 3–5 cm long taken from non-flowering shoots in summer root easily in gritty, sharply drained compost; overwinter rooted cuttings under glass in cooler climates. 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

Cosson's Germander is mildly toxic to pets. Teucrium cossonii is not recorded on the ASPCA Toxic and Non-Toxic Plant database. The Teucrium genus contains neo-clerodane diterpenoids, a compound class linked to hepatotoxic effects; while documentation for this specific species is limited, it should be treated as mildly toxic to cats and dogs. Gastrointestinal upset may result from ingestion. Keep away from pets and seek veterinary guidance if consumption occurs. 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.

Cosson's Germander care — frequently asked questions

What is the common name for Teucrium cossonii?

Teucrium cossonii is most commonly called Cosson's Germander, but it is also known as Cosson's germander, Balearic germander. The names refer to the same species, so care instructions for Cosson's Germander apply identically to anything sold as Balearic germander.

How much light does cosson's germander need?

Cosson's Germander grows best in direct sun (at least 4-6 hours). Requires maximum sun to flower prolifically and maintain the characteristic silver felting; in shade the plant etiolates and loses its neat prostrate habit.

How often should I water cosson's germander?

Water cosson's germander sparingly every 2–3 weeks in summer; minimal to none in winter. Exceptionally drought-tolerant in free-draining soil; the woolly grey foliage reflects heat and reduces water loss. Any standing winter moisture around the crown is fatal. 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 cosson's germander toxic to cats and dogs?

Cosson's Germander is mildly toxic to pets. Teucrium cossonii is not recorded on the ASPCA Toxic and Non-Toxic Plant database. The Teucrium genus contains neo-clerodane diterpenoids, a compound class linked to hepatotoxic effects; while documentation for this specific species is limited, it should be treated as mildly toxic to cats and dogs. Gastrointestinal upset may result from ingestion. Keep away from pets and seek veterinary guidance if consumption occurs.

What USDA hardiness zone does cosson's germander grow in?

Cosson's Germander is rated for USDA zone 7-10 and RHS hardiness H4. Outside that range, grow it as a container plant that overwinters indoors before the first hard frost.

Cosson's Germander deep-dive guides

Every aspect of cosson's germander care, each with its own calibrated guide:

Featured in these plant shortlists

Cosson's Germander qualifies for 5 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

Related guides

Cosson's Germander is also commonly called Cosson's germander or Balearic germander.