Ornamental · Asteraceae
Calendula
Calendula officinalis
In full sun on lean soil, pot marigold opens its yellow-to-orange heads from spring to frost.
Full sun
Every 3–7 days
39–75°F · 4–24°C
45–65 days
Overview
Calendula, the pot marigold, is a cool-season annual in the daisy family whose flower heads sit like flat or rounded rosettes of strap-shaped ray petals, glowing bright yellow to deep orange above soft, slightly sticky green leaves. Sow it once and the heads open from spring into fall, after which the plant drops its curved seed and returns the next year. Those ray petals are edible, which is why cooks pull them loose to scatter over salads and tint food a warm gold.
It comes along on very little. Plain, well-drained soil and a place in full sun are enough, and the plant actually sets more of those vivid heads when the feeding stays light. Real summer heat leaves the foliage limp and the flowering thin, yet a hard cutback often pushes a fresh crop of buds and color once fall cools the air.
The plant builds a low, branching mound of pale green, lance-shaped leaves with the flower heads held just above on sturdy stems. A little deadheading and dry foliage to fend off the white dust of mildew are all it takes, and calendula carries its color at the front of a bed with very little fuss.
Care
The short version: full sun, plain well-drained soil, and a light hand with fertilizer. Keep the soil evenly moist at the base, pinch off the spent heads, and the yellow-to-orange flowers keep coming cool-season from spring through fall.
Light
Calendula opens the most heads in full sun, though it will take partial shade where summers turn hot. The more sun strikes the foliage, the more buds it pushes, so the brightest spot draws out the deepest color.
Water
Keep the soil evenly moist with regular watering, over ground that drains so the roots never sit wet. Water at the base rather than over the leaves, since droplets left on those soft green surfaces invite the white film of powdery mildew. Its overall thirst is only medium.
Soil
Average, well-drained soil is all it wants, and it takes clay, loam, sand, or rich ground without complaint. A pH anywhere from 5.5 to 7.0 suits it. Drainage at the roots matters more here than how rich the soil is.
Temperature
This is a cool-weather plant, holding its leaves firm and its color clear from about 39°F to 75°F (4°C to 24°C). In midsummer heat the foliage wilts and the heads thin, then both fill back in as fall cools the air.
Humidity
Ordinary outdoor humidity is no trouble, so there is no number to chase. Air movement matters more than the reading, since crowded, damp plants are the ones that pick up the white mildew bloom.
Feeding
Feed lightly, if at all, through the growing season. Calendula blooms best on lean soil, and a heavy feed swells the leaves while the flower heads thin out.
Pruning
Pinch off the spent heads as the petals fade and brown to keep fresh buds forming and to curb self-seeding. If the plant flags in summer heat, cut it back hard and it often pushes a new crop of color once fall arrives.
Size & spacing
The plant builds a mound about 12 to 24 inches (30 to 61 cm) tall and roughly as wide. Give each one that much room so air moves through the leaves and mildew finds less of a foothold.
When to plant
Calendula is a cool-season annual that throws its best color in the mild weather at either end of summer. Start the seed indoors in late winter or press it into the ground around the last frost, and the heads keep opening from spring until a hard frost finally browns and closes them.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: About 6 to 8 weeks before the last spring frost
- Plant: Direct sow or transplant just before to around the last spring frost; a cool-season annual best in spring and fall
- Harvest: Blooms spring through summer, continuing almost nonstop until first heavy frost in cool climates
Hardiness
USDA hardiness zones: 2–11
Temperature: down to -46°C
Troubleshooting
Calendula is tough, and most of what ails it shows up right on the leaves or the new growth, written plainly in spots, holes, or twisted shapes. Read the symptom early and a quick fix usually settles it. Match what you see below, then act before it spreads.
Yellow-green marbling and crinkled, twisted leaf blades
Leaves blotched in a yellow-green mosaic and pulled into twisted, puckered shapes that water and feeding never smooth out signal cucumber mosaic virus, which aphids carry from one plant to the next. Nothing reverses the damage, so any plant showing the mottling gets dug out and destroyed before it reaches its neighbors. Keeping the aphids down and washing your hands between plants slows how far the virus travels.
Fix:
- Remove and destroy infected plants to limit spread
- Control aphid vectors
- Avoid handling healthy plants after touching infected ones
Ghostly flour-like dust filming the leaf surfaces
A chalky white film dusted across the leaves and stems is powdery mildew, a fungus that settles in where plants crowd together in still, humid air. Open up the spacing so air can drift through, water at the base to keep the leaf surfaces dry, and strip off any leaf gone thickly furred with the coating. Full sun and a little room between plants keep the white bloom from creeping back.
Fix:
- Improve air circulation by thinning and spacing plants
- Water at the base to keep foliage dry
- Remove and discard severely affected leaves
Glistening residue and tiny bodies packed along soft new tips
The tiny soft-bodied specks, green or black, pressed in tight along the newest shoots and the swelling buds are aphids, drawn to the softest, most succulent tissue. A hard jet of water knocks them loose from the stems, and insecticidal soap clears a thick run of them. Holding back on high-nitrogen feeding starves out the soft growth they cluster on, and lady beetles pick off what is left.
Fix:
- Spray plants with a strong stream of water to dislodge aphids
- Apply insecticidal soap if populations are high
- Encourage beneficial insects such as lady beetles
Tattered edges and gouged holes across petals and foliage
Torn, irregular holes punched through the leaves and petals, with a glistening slime trail nearby, mark slugs and snails, which feed after dark and chew through soft young plants first. Step out at dusk with a flashlight and lift them off the foliage by hand, then rake away the damp debris they shelter under by day. Iron-phosphate baits or simple traps thin them out when the ragged chewing keeps spreading.
Fix:
- Hand-pick slugs and snails in the evening
- Remove garden debris that provides shelter
- Use traps or iron-phosphate baits if damage is heavy
Toxicity
The news here is reassuring. The ASPCA lists pot marigold as non-toxic to cats, dogs, and horses, and the soft ray petals are edible for people too. A grazing pet or a curious child mouthing a leaf is in no danger, so it can go anywhere in the garden.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
The ASPCA lists pot marigold as non-toxic to cats, so a mouthful of the soft petals or leaves does no harm.
Dogs None
Dogs are safe with it too. This is the garden pot marigold, not the bedding type, and the ASPCA rates it safe.
Horses Safe
Calendula carries no known toxic compounds, so a horse cropping the leaves and flower heads is unharmed.
Rabbits Safe
Rabbits can browse the tender leaves and ray petals safely, and the flowers are often grown as a safe forage.
Livestock Safe
Cattle, goats, and sheep graze calendula without trouble, with no reports of poisoning.
Birds Safe
Backyard birds can pick at the dried seed heads and loose petals safely.
People Safe
The ray petals are edible, scattered through salads and used as a saffron-style coloring, so people have nothing to watch out for.
Varieties
Calendula opens in a handful of flower forms and color depths worth telling apart before you sow. These are the ones you will see most.
Double-flowered types
These pack a full, rounded head with rank upon rank of overlapping petals in yellow through deep orange, dense where the single form sits open.
Single-flowered types
These open into a flat daisy face, a single rim of strap-like ray petals encircling a low, flat central disk.
Yellow to orange color forms
These flush from clear bright yellow to a deep saturated orange, the edible ray petals tearing free easily for a garnish or natural coloring.
How to propagate
Calendula spreads from its curved, ridged seed and little else, but it does that with almost no help, sprouting fast and reseeding itself for the next year.
SeedEasy
Start indoors about 6 to 8 weeks before the last frost, or direct sow outdoors around the last spring frost · Germinates in about 5 to 15 days; first blooms in roughly 45 to 65 days from seed
Calendula grows readily from its curved, ridged seed, one of the simplest flowers to raise this way. Set the seed about 1/4 to 1/2 inch deep, sowing indoors 6 to 8 weeks before the last frost or straight into the ground around frost. Green seedlings push up in 5 to 15 days, and the first flower heads unfurl within 45 to 65 days. Left standing, the plant scatters its own seed and reseeds for next year, though never thickly enough to crowd out the bed.
Myths
Those golden calendula heads are just bedding marigolds under a different name, and their tissues are mildly toxic to animals.
Pot marigold is Calendula officinalis, a separate genus from the Tagetes bedding marigolds it is so often mistaken for. The ASPCA lists it as non-toxic to dogs and cats, so the toxicity worry attached to that mix-up falls away.
Those glowing orange heads only come on when the plant sits in rich, heavily fertilized ground.
It comes along well on average, well-drained ground and wants very little. Heavy feeding actually works against the flowers, swelling the leaves at the expense of the blooms, so go light on the fertilizer.