How-to Guide
How to Grow Calendula (Pot Marigold)
The short answer
Sow calendula seed directly in spring once soil temperatures reach 60°F, a quarter-inch deep; seedlings emerge in 1-2 weeks, and get thinned to 8-12 inches apart (Utah State University Extension). Transplants can go out after frost danger has passed. Full sun to part shade, well-drained moderately rich soil, pH 6-7.
Calendula is a cool-season bloomer: it prefers temperatures under 85°F, often stops flowering in extreme heat, then roars back in fall — and it survives cold down to 25°F. Deadhead to keep blooms coming and to stop it from self-seeding all over the bed.
When and How to Sow
- 1Wait for 60°F soil — Direct sow in spring once soil temperatures reach 60°F (USU Extension).
- 2Sow shallow — Plant seeds ¼ inch deep; germination takes 1-2 weeks.
- 3Thin hard — Thin seedlings to 8-12 inches apart — crowded calendula gets mildew.
- 4Or transplant — Set out transplants after danger of frost has passed.
Sun, Soil, and Water
Calendula grows in full sun to part shade in well-drained, moderately nutrient-rich soil with a pH of 6-7 (USU Extension). It tolerates low water, but for steady bloom give it 1 to 1.5 inches of water per week in midsummer. Avoid overwatering — it's more drought-proof than rot-proof.
A monthly side-dress with a complete soluble fertilizer keeps plants (8 to 24 inches tall, depending on variety) producing.
The Cool-Season Rhythm
Calendula prefers temperatures below 85°F and often stops blooming in extreme heat, then resumes as fall cools — University of Minnesota Extension flags it as a reliable cool-season annual for exactly this reason. It survives temperatures down to 25°F, so it keeps flowering past the first light frosts that kill tender annuals (USU Extension).
Deadheading and Self-Seeding
Deadheading spent flowers encourages rebloom. It also matters for control: calendula self-seeds readily if not deadheaded and can turn weedy. Decide which you want — a self-renewing patch or a tidy bed — and deadhead accordingly (USU Extension).
✔ The petals are edible, with a slightly salty taste (USU Extension) — scatter them on salads. Use only flowers you know haven't been sprayed.
Common Problems
- Whiteflies and aphids — a hard water spray or insecticidal soap handles them (USU Extension).
- Powdery mildew — give plants good air circulation and avoid overhead watering.
- Summer bloom pause — heat, not disease; wait for fall.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- Utah State University Extension — How to Grow Calendula in Your Garden — Sow at 60°F soil, ¼ inch deep, thin to 8-12 inches; pH 6-7; 1-1.5 inches water/week; deadheading for rebloom; prefers <85°F, survives to 25°F; edible petals; self-seeds if not deadheaded; pest/disease list
- University of Minnesota Extension — Year of the Calendula — Calendula thrives in cool weather, may pause blooming in hot summers, and rebounds with fall color