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Plant care

Nettle-leaved Mullein (Chaix's Mullein) care

Verbascum chaixii

Also called Nettle-leaved Mullein, Chaix's Mullein, Chaixii Mullein.

RHS H6USDA 5–9Mildly toxic to petsIndoor Height 90–120 cm (3–4 ft) in flower

Watering rhythm

10-14days

Every 10–14 days during dry spells; seldom needed once established

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Light

Direct sun (at least 4-6 hours)

Soil

Well-drained, low to moderately fertile loam, chalk, or sandy soil

Humidity

35–65% RH

Temp

-20 to 30°C

Pet safety

Mildly toxic to pets

Mature size

Height 90–120 cm (3–4 ft) in flower

Care at a glance

Light

Aim for at least 4-6 hours of direct sun on the leaves. Best in full sun (6+ hours daily). Tolerates very light afternoon shade, especially in hotter climates, but flowering output and stem strength are reduced in shadier spots. If your only bright window faces south, that's perfect for nettle-leaved mullein — same window any aroid would fry on.

Watering

Watering nettle-leaved mullein: every 10–14 days during dry spells; seldom needed once established. 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. Highly drought-tolerant once roots are established. Water regularly in the first season. Soggy or poorly drained soils, especially in winter, are the primary cause of death. Very little supplemental irrigation needed in UK climates.

Soil and pot

Nettle-leaved Mullein grows best in well-drained, low to moderately fertile loam, chalk, or sandy soil. Prefers alkaline to neutral pH (6.5–7.5). Unlike the biennials, V. chaixii tolerates a slightly heavier soil provided drainage is adequate. Avoid waterlogged clay. 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

Nettle-leaved Mullein sits happiest at around 35–65% RH humidity and -20 to 30°C (-4 to 86°F). Tolerates a wide humidity range. Ensure good airflow around the basal rosette, particularly in humid summers, to reduce risk of fungal leaf spots. 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 nettle-leaved mullein sparingly. Minimal. An annual top-dressing of low-nitrogen fertiliser (e.g. bonemeal or 5-10-10) in early spring is adequate. Avoid high nitrogen, which produces soft, floppy growth prone to flopping. 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 nettle-leaved mullein in the Growli community. Each is annotated with the most common cause so you know where to start.

  • Powdery mildew — Can occur in humid, crowded conditions, especially later in summer. Plant in open, sunny spots with good airflow. Generally cosmetic; cut affected foliage back after flowering.
  • Verbascum moth caterpillars (Cucullia verbasci) — Yellow-and-black patterned caterpillars strip foliage and flowers in early summer. Hand-pick to control; plants usually recover and reflower if damage occurs before peak bloom.
  • Crown rot in winter wet — Even the perennial V. chaixii resents prolonged wet at the crown. On heavy soils, incorporate grit at planting or mulch around (not over) the crown with gravel.

Propagation

Division of established clumps in early spring, or root cuttings taken in late autumn/early winter (3–4 cm sections laid horizontally in gritty compost). Also readily raised from seed sown at the soil surface at 15–20°C in spring; will flower in year two. Self-seeds moderately. 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

Nettle-leaved Mullein is mildly toxic to pets. Verbascum chaixii is not individually listed by the ASPCA. Like other mullein species, it contains saponins and may cause mild gastrointestinal upset if ingested in quantity. The hairy foliage can also irritate skin. Not considered severely hazardous but treat with caution around pets and children. 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.

Nettle-leaved Mullein care — frequently asked questions

What is the common name for Verbascum chaixii?

Verbascum chaixii is most commonly called Nettle-leaved Mullein, but it is also known as Nettle-leaved Mullein, Chaix's Mullein, Chaixii Mullein. The names refer to the same species, so care instructions for Nettle-leaved Mullein apply identically to anything sold as Chaix's Mullein.

How much light does nettle-leaved mullein need?

Nettle-leaved Mullein grows best in direct sun (at least 4-6 hours). Best in full sun (6+ hours daily). Tolerates very light afternoon shade, especially in hotter climates, but flowering output and stem strength are reduced in shadier spots.

How often should I water nettle-leaved mullein?

Water nettle-leaved mullein every 10–14 days during dry spells; seldom needed once established. Highly drought-tolerant once roots are established. Water regularly in the first season. Soggy or poorly drained soils, especially in winter, are the primary cause of death. Very little supplemental irrigation needed in UK climates. 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 nettle-leaved mullein toxic to cats and dogs?

Nettle-leaved Mullein is mildly toxic to pets. Verbascum chaixii is not individually listed by the ASPCA. Like other mullein species, it contains saponins and may cause mild gastrointestinal upset if ingested in quantity. The hairy foliage can also irritate skin. Not considered severely hazardous but treat with caution around pets and children.

What USDA hardiness zone does nettle-leaved mullein grow in?

Nettle-leaved Mullein is rated for USDA zone 5–9 and RHS hardiness H6. Outside that range, grow it as a container plant that overwinters indoors before the first hard frost.

Nettle-leaved Mullein deep-dive guides

Every aspect of nettle-leaved mullein care, each with its own calibrated guide:

Featured in these plant shortlists

Nettle-leaved Mullein qualifies for 4 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

Related guides

Nettle-leaved Mullein is also known as Nettle-leaved Mullein, Chaix's Mullein, and Chaixii Mullein.