Calendula 'Radio' (Radio pot marigold) care

Light

Aim for at least 4-6 hours of direct sun on the leaves. Full sun for the densest, most colourful blooms. Tolerates light shade and actually flowers longer where summers are very hot, cooler conditions extending the display. If your only bright window faces south, that's perfect for calendula 'radio' — same window any aroid would fry on.

Watering

Watering calendula 'radio': water when the top 2-3 cm of soil is dry, roughly weekly. 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. Keep evenly moist while establishing and flowering; it is fairly drought-tolerant once grown but blooms better with steady moisture. Avoid waterlogging and water at the base.

Soil and pot

Calendula 'Radio' grows best in average, well-drained soil, ph 6.0-7.0. Undemanding; thrives in ordinary garden soil and even poor ground. Good drainage matters more than fertility, and overly rich soil favours leaf over flower. 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

Calendula 'Radio' sits happiest at around Outdoor ambient humidity and 5-25°C (41-77°F). Untroubled by humidity, though damp, crowded plantings invite powdery mildew. Space plants for airflow. No special humidity provision needed. If you keep the room above 5 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 calendula 'radio' sparingly. Light feeder. Compost-enriched soil is usually enough; a monthly low-nitrogen or balanced feed in poor soil supports flowering, but avoid high nitrogen, which favours foliage. 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 calendula 'radio' in the Growli community. Each is annotated with the most common cause so you know where to start.

• Powdery mildew — Grey-white coating in humid, crowded conditions or late season. Space plants, water at the base, and remove affected leaves.
• Aphids — Cluster on buds and shoot tips. Hose off or use insecticidal soap; calendula also attracts aphid predators as a companion plant.
• Stops flowering / sets seed — Seed-setting halts bloom and heat can stall it. Deadhead regularly and the cool-season display lasts far longer.
• Leggy, sparse plants — Caused by shade or rich soil. Grow in full sun and pinch young plants to encourage bushy, floriferous growth.

Propagation

From seed, direct-sown or started indoors; quick and reliable to germinate, often self-seeding. Sow in spring (or autumn in mild areas) and thin to about 30 cm apart. 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

Calendula 'Radio' is pet-safe. The ASPCA lists Pot Marigold (Calendula officinalis) as non-toxic to cats and dogs, with no toxic principle. Note this is distinct from true marigolds (Tagetes), which are mildly toxic. Eating large amounts may still cause mild stomach upset, as with any 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.

Calendula 'Radio' deep-dive guides

Every aspect of calendula 'radio' care, each with its own calibrated guide:

• Calendula 'Radio' watering schedule
• Calendula 'Radio' light requirements
• Best soil mix for calendula 'radio'
• Calendula 'Radio' fertilizing guide
• When to repot calendula 'radio'
• How to propagate calendula 'radio'
• Calendula 'Radio' growth rate & size
• Calendula 'Radio' cold hardiness
• Calendula 'Radio' temperature & humidity
• Is calendula 'radio' toxic to cats & dogs?
• Is calendula 'radio' toxic to cats?
• Is calendula 'radio' toxic to dogs?
• Getting calendula 'radio' to bloom

Featured in these plant shortlists

Calendula 'Radio' qualifies for 11 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

• Best pet-safe houseplants — Houseplants the ASPCA lists as non-toxic to cats and dogs — every one verified against the ASPCA toxic and non-toxic plant list.
• Best drought-tolerant houseplants — Houseplants that prefer to dry out — forgiving of forgotten watering and ideal for travel or busy weeks.
• Best flowering houseplants — Indoor plants grown for their blooms — selected from the flowering species in Growli’s plant-care library.
• Best pet-safe low-maintenance plants — Non-toxic to cats and dogs and forgiving of forgotten watering — the easiest safe choices for a busy pet household.
• Best pet-safe flowering plants — Flowering houseplants the ASPCA lists as non-toxic to cats and dogs — colour and blooms in a pet home, without the worry.
• Best pet-safe plants for bright light — Non-toxic to cats and dogs and happy in a bright, sunny spot — safe plants for your best-lit windowsill.
• Best houseplants for full sun — Houseplants that want direct sun — the species for a hot south or west-facing windowsill where shade-lovers scorch.
• Best houseplants for a cool room — Houseplants that tolerate cool conditions down to about 10°C — for an unheated spare room, hallway, porch or a home kept cool.
• Best fast-growing houseplants — Houseplants documented as fast or vigorous growers — quick to fill a pot, cover a pole or trail down a shelf.
• Best cat-safe plants — Houseplants the ASPCA lists as non-toxic to cats (and dogs) — safe greenery for a home with a curious cat.
• Best dog-safe plants — Houseplants the ASPCA lists as non-toxic to dogs (and cats) — safe greenery for a home with a curious dog.
• Browse all 29 plant shortlists — pet-safe, low-light, drought-tolerant and more

Related guides

Calendula 'Radio' is also commonly called Radio pot marigold or quilled marigold.

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