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Plant care

Hollyhock care

Althaea rosea

Also called Hollyhock, Common Hollyhock, Rose Hollyhock.

RHS H7USDA 3-9Pet-safeIndoor 150–270 cm tall (5–9 ft) and 45–60 cm wide

Watering rhythm

Direct sun (at least 4-6 hours)

Weekly during active growth; reduce in autumn and winter

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Light

Direct sun (at least 4-6 hours)

Soil

Deep, fertile, well-drained loam

Humidity

40–65%

Temp

-34°C to 35°C

Pet safety

Pet-safe

Mature size

150–270 cm tall (5–9 ft) and 45–60 cm wide

Care at a glance

Light

Aim for at least 4-6 hours of direct sun on the leaves. Requires full sun — minimum 6 hours of direct sunlight daily. Insufficient light leads to weak, floppy stems and reduced flowering. A south- or west-facing position against a wall is ideal, providing warmth and shelter. If your only bright window faces south, that's perfect for hollyhock — same window any aroid would fry on.

Watering

Watering hollyhock: weekly during active growth; reduce in autumn and 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 and infrequently at the base, keeping foliage dry to minimise rust fungus. Do not allow to dry out during flowering. Established plants tolerate short dry periods but perform best with consistent moisture.

Soil and pot

Hollyhock grows best in deep, fertile, well-drained loam. Hollyhocks develop a deep taproot and prefer rich, fertile, moisture-retentive but well-drained soil at pH 6.0–8.0. They tolerate alkaline soils well. Amend sandy or thin soils with well-rotted manure or compost before planting. 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

Hollyhock sits happiest at around 40–65% humidity and -34°C to 35°C (-30°F to 95°F). Prefers moderate humidity. High humidity and poor air circulation greatly increase the risk of hollyhock rust (Puccinia malvacearum), the most serious common problem. Space plants 45–60 cm apart for airflow. 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 hollyhock sparingly. Incorporate well-rotted compost or manure at planting. Top-dress with a balanced fertiliser (e.g. 10-10-10) in spring. During bud formation, switch to a potassium-rich feed (e.g. tomato fertiliser) to encourage flowering. Avoid excess nitrogen which produces lush leaves and poor blooms. 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 hollyhock in the Growli community. Each is annotated with the most common cause so you know where to start.

  • Hollyhock rust (Puccinia malvacearum) — The most common problem: orange-brown pustules on leaf undersides and yellow spots above, causing premature defoliation. Improve air circulation, remove infected leaves, and apply sulphur- or copper-based fungicide from early spring. Treat plants as disposable annuals and start fresh from seed each year to reduce inoculum.
  • Slugs and snails — Young seedlings and basal leaves are vulnerable to slug damage, especially in damp springs. Use slug pellets (ferric phosphate), copper tape, or nematode drenches. Raise seedlings under cover and harden off before transplanting.
  • Hollyhock weevil (Apion longirostre) — Larvae develop inside seed pods, destroying seeds before they ripen. Collect and destroy affected pods. For seed saving, hand-pollinate and bag flowers early.

Propagation

Sow seed directly where plants are to grow in early summer (biennials flower the following year). Can also be sown indoors in early spring at 18°C / 65°F. Self-seeds prolifically; allow some seed heads to drop naturally. Single-flowered cultivars come reliably true from seed; double-flowered types are better propagated by basal cuttings in spring. 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

Hollyhock is pet-safe. Althaea rosea (hollyhock) is listed by ASPCA as non-toxic to dogs and cats. The plant contains mucilaginous polysaccharides that are harmless; mild GI upset is possible if large amounts are consumed but it is not considered a toxic plant. 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.

Hollyhock care — frequently asked questions

What is Hollyhock?

Hollyhock (Althaea rosea) is a flowering plant with a tall, upright biennial or short-lived perennial with a single main flowering spike and large, lobed basal leaves growth habit, reaching 150–270 cm tall (5–9 ft) and 45–60 cm wide at maturity. Althaea rosea (syn. Alcea rosea) is a stately biennial or short-lived perennial producing tall spires of large, papery flowers in shades of pink, red, white, yellow, and near-black.

How much light does hollyhock need?

Hollyhock grows best in direct sun (at least 4-6 hours). Requires full sun — minimum 6 hours of direct sunlight daily. Insufficient light leads to weak, floppy stems and reduced flowering. A south- or west-facing position against a wall is ideal, providing warmth and shelter.

How often should I water hollyhock?

Water hollyhock weekly during active growth; reduce in autumn and winter. Water deeply and infrequently at the base, keeping foliage dry to minimise rust fungus. Do not allow to dry out during flowering. Established plants tolerate short dry periods but perform best with consistent moisture. 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 hollyhock toxic to cats and dogs?

Hollyhock is pet-safe. Althaea rosea (hollyhock) is listed by ASPCA as non-toxic to dogs and cats. The plant contains mucilaginous polysaccharides that are harmless; mild GI upset is possible if large amounts are consumed but it is not considered a toxic plant.

What USDA hardiness zone does hollyhock grow in?

Hollyhock is rated for USDA zone 3-9 and RHS hardiness H7. Outside that range, grow it as a container plant that overwinters indoors before the first hard frost.

Hollyhock deep-dive guides

Every aspect of hollyhock care, each with its own calibrated guide:

Featured in these plant shortlists

Hollyhock qualifies for 10 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

Related guides

Hollyhock is also known as Hollyhock, Common Hollyhock, and Rose Hollyhock.