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How to Grow Hollyhock

Alcea rosea

Hardy Any Season Single Harvest

When to Start

Direct sow outdoors as soon as soil reaches 8°C — typically early to mid spring. Hardy enough to tolerate light frosts.

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Growth Stages

Sow seeds
Germination ~14d
Flowering ~365d

Approximate days from start

Care Essentials

  • Feed with a balanced fertiliser in spring as growth begins, then switch to a high-potash feed monthly during the flowering season to prolong blooms.
  • Hollyhocks are short-lived perennials often grown as biennials. Sow in summer for flowers the following year. Self-seeding freely — allow some seed to fall to maintain a colony.

Companion Planting

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Growing Conditions

Min. soil temperature: 8°C+
Germination temperature: 15–21°C

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Spacing & Planting

Plant spacing 45 cm
Row spacing 60 cm
Sow depth 0.5 cm
Mature height 200 cm
Mature spread 45 cm

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Care Guide

Feeding
Feed with a balanced fertiliser in spring as growth begins, then switch to a high-potash feed monthly during the flowering season to prolong blooms.
Watch for
  • Hollyhock rust (Phragmidium malvacearum)
  • Slug and snail damage on young plants
  • Aphids
  • Leaf spot

Pests & Diseases

Pest Aphids

Identification: Clusters of small soft-bodied insects on shoot tips and flower buds, often accompanied by sticky honeydew and sooty mould.

Organic treatment:
  • Blast off with a strong jet of water. Encourage predators by planting nectar-rich companions nearby.
  • Spray with a dilute soft soap or neem oil solution, coating stems and the undersides of leaves.
Chemical treatment:
  • Apply a pyrethrin-based insecticide as a last resort, avoiding open flowers to protect pollinators.
Pest Slugs and Snails

Identification: Ragged holes in young leaves and stems, silvery slime trails visible in the morning, particularly on seedlings and newly transplanted hollyhocks.

Organic treatment:
  • Apply a generous ring of sharp grit, crushed eggshells, or copper tape around the base of each plant.
  • Use wildlife-safe ferric phosphate pellets (e.g. Slug Gone) according to label instructions.
Chemical treatment:
  • Metaldehyde-based slug pellets are now banned in the UK. Use only ferric phosphate or other approved alternatives.
Pest Hollyhock Weevil

Identification: Small elongated beetles feeding on leaves, leaving a characteristic shot-hole pattern; larvae may feed inside seed pods.

Organic treatment:
  • Remove adults by hand in early morning when they are sluggish. Destroy infested seed pods.
Chemical treatment:
  • A contact insecticide containing lambda-cyhalothrin can be applied if populations are high, avoiding flowering periods.
Disease Hollyhock Rust Phragmidium malvacearum

Symptoms: Bright orange or yellow pustules on the undersides of leaves; corresponding pale yellow spots on the upper surface. Severely affected leaves turn brown and drop.

Treatment: Remove and bin all infected leaves immediately. Do not compost. Apply a copper-based fungicide or sulphur dust to remaining foliage after clearing.

Prevention: Ensure good air circulation by not overcrowding plants. Avoid overhead watering. Grow resistant varieties where possible and clear all debris at the end of the season.

Disease Leaf Spot Cercospora althaeina

Symptoms: Circular brown or grey spots with darker margins on leaves, sometimes with a pale centre. Spots may coalesce under heavy infection, causing leaves to yellow and drop.

Treatment: Remove affected leaves and improve air circulation. A copper-based fungicide can reduce spread in severe cases.

Prevention: Water at the base rather than overhead. Avoid planting in damp, shaded spots. Clear fallen leaves promptly at season's end.

Growing Conditions

Min. soil temperature8°C
Germination temperature15–21°C
Base growth temperature5°C
Min. daylength to start10h
Photoperiod sensitivityday neutral

Frequently Asked Questions

How far apart should I plant Hollyhock?
Plant Hollyhock 45cm apart with 60cm between rows.
Is Hollyhock frost hardy?
Hollyhock is classified as Hardy.

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