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Chrysanthemum 'Snowdon' (Snowdon mum) care

Chrysanthemum 'Snowdon'

Also called Snowdon mum, white chrysanthemum, hardy mum.

RHS H5USDA 5-9Toxic to petsIndoor 60-80 cm tall

Watering rhythm

5-7days

When the top 2-3 cm of soil is dry, roughly every 5-7 days during the growing season

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Light

Direct sun (at least 4-6 hours)

Soil

Fertile, well-drained loam with added organic matter

Humidity

40-60%

Temp

4-22°C

Pet safety

Toxic to pets

Mature size

60-80 cm tall

Care at a glance

Light

Chrysanthemum 'Snowdon' needs sun on the leaves, not just bright ambient room light. Full sun is required; at least 6 hours of direct sunlight produces the compact habit and pure white blooms this cultivar is known for. Shade causes lax stems and greening of the white flowers. 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 chrysanthemum 'snowdon' when the top 2-3 cm of soil is dry, roughly every 5-7 days during the growing season. 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. Keep soil evenly moist from spring to flowering. Water at the base to protect the white petals from botrytis. Reduce watering in winter once the plant has died back.

Soil and pot

Chrysanthemum 'Snowdon' grows best in fertile, well-drained loam with added organic matter. Dig in garden compost or well-rotted manure before planting to enrich the soil. Good drainage prevents root and crown rot, which is especially important in the UK's wet winters. 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

Chrysanthemum 'Snowdon' sits happiest at around 40-60% humidity and 4-22°C (39-72°F). Ambient outdoor humidity is generally fine. White flowers are particularly susceptible to brown spotting from botrytis in humid, still conditions — space plants 40-50 cm apart and site in an open, airy position. If you keep the room above 4 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 chrysanthemum 'snowdon' sparingly. Apply a balanced slow-release granular fertiliser in early spring. From July, switch to a high-potassium liquid feed fortnightly to support bud set and strengthen the stems for the large white flowers. 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 chrysanthemum 'snowdon' in the Growli community. Each is annotated with the most common cause so you know where to start.

  • Botrytis on white blooms — Brown spotting on petals in damp conditions; plant in full airflow and avoid wetting flowers when watering.
  • Aphids — Particularly visible against pale stems; knock off with a water jet or treat with insecticidal soap.
  • Powdery mildew — White powder on foliage mid-season; remove worst-affected leaves and increase spacing.
  • Earwigs — Damage petals overnight; place inverted pots filled with straw near plants as traps.
  • Winter crown rot — Caused by wet, poorly drained soil; mulch crowns in autumn and ensure drainage is sharp.

Companion plants

Chrysanthemum 'Snowdon' pairs well with Aster novae-angliae, Helenium autumnale, Pennisetum alopecuroides, and Anemone x hybrida. These are species with similar light and water needs, so you can group them in the same room or on the same shelf and water as a batch.

Propagation

Divide clumps every 2-3 years in spring; replant outer sections in refreshed soil. Softwood basal cuttings taken in spring root in 3-4 weeks in a humid propagation environment. 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

Chrysanthemum 'Snowdon' is toxic to pets. Chrysanthemum species are ASPCA-listed as toxic to dogs, cats, and horses. Contact with or ingestion of any plant part can cause vomiting, diarrhoea, hypersalivation, incoordination, and skin irritation from pyrethrin and sesquiterpene lactone compounds. 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.

Chrysanthemum 'Snowdon' care — frequently asked questions

What is the common name for Chrysanthemum 'Snowdon'?

Chrysanthemum 'Snowdon' is most commonly called Chrysanthemum 'Snowdon', but it is also known as Snowdon mum, white chrysanthemum, hardy mum. The names refer to the same species, so care instructions for Chrysanthemum 'Snowdon' apply identically to anything sold as Snowdon mum.

How much light does chrysanthemum 'snowdon' need?

Chrysanthemum 'Snowdon' grows best in direct sun (at least 4-6 hours). Full sun is required; at least 6 hours of direct sunlight produces the compact habit and pure white blooms this cultivar is known for. Shade causes lax stems and greening of the white flowers.

How often should I water chrysanthemum 'snowdon'?

Water chrysanthemum 'snowdon' when the top 2-3 cm of soil is dry, roughly every 5-7 days during the growing season. Keep soil evenly moist from spring to flowering. Water at the base to protect the white petals from botrytis. Reduce watering in winter once the plant has died back. 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 chrysanthemum 'snowdon' toxic to cats and dogs?

Chrysanthemum 'Snowdon' is toxic to pets. Chrysanthemum species are ASPCA-listed as toxic to dogs, cats, and horses. Contact with or ingestion of any plant part can cause vomiting, diarrhoea, hypersalivation, incoordination, and skin irritation from pyrethrin and sesquiterpene lactone compounds.

What USDA hardiness zone does chrysanthemum 'snowdon' grow in?

Chrysanthemum 'Snowdon' 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.

Chrysanthemum 'Snowdon' deep-dive guides

Every aspect of chrysanthemum 'snowdon' care, each with its own calibrated guide:

Featured in these plant shortlists

Chrysanthemum 'Snowdon' 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

Chrysanthemum 'Snowdon' is also known as Snowdon mum, white chrysanthemum, and hardy mum.