How to Grow Calendulas USA

At a Glance

Quick Facts

Factor	Value
Drainage	Well-drained; light, poor, free-draining soil tolerated (RHS). USU: moderately nutrient-rich, tolerates a wide range.
Lifecycle	Hardy annual (RHS also lists a biennial habit). Genuinely distinct from the Tagetes marigolds already in this catalogue (French/Aztec marigold, Signet marigold) -- Calendula and Tagetes share the common name "marigold" but are different genera. Flowers from summer through early autumn (RHS).
Edible parts	flowers, leaves

Growth Stages

Stage	BBCH	Notes
Sowing	0	RHS: sow direct in spring (or autumn), 0.5cm deep into finely prepared soil, thinned to 23cm apart; sow at 2-3 week intervals for a continuous display. USU: sow 1/4in deep once soil temperature reaches 60°F, germinates in 1-2 weeks; thin seedlings to 8-12in apart in the row.
Establishment care	3	USU: supply 1-1.5in of water a week in mid-summer for optimal growth, though the plant can survive low-water conditions; side-dress every month with a complete soluble fertilizer for optimal bloom.
Flowering and companion planting	6	Deadhead regularly and pinch out terminal shoots to encourage bushy growth and prolong flowering (RHS; USU); USU gives a concrete number -- plants re-bloom in about 2 weeks after deadheading. USU: often planted around tomatoes and potatoes as a companion, acting as a trap crop that draws aphids, whiteflies and thrips away with its sticky sap. Self-seeds readily year to year (RHS).
Harvest	8	USU: pick the complete flower head at full bloom; dry in 1-5 days in a ventilated area away from sunlight. RHS: flowers good for cutting, petals edible, used both in cooking and by herbalists for skincare; USU adds the leaves are also edible, often added to salads.

Harvest & Storage

When to pick: USU: pick the complete flower head at full bloom; plants re-bloom in about 2 weeks after deadheading. RHS: flowers good for cutting.

Storage

USU: dry flowers in 1-5 days in a ventilated area away from sunlight.

Diseases

Powdery mildew

low

Named by both RHS and USU ("powdery mildew(s)").

Calendula virus diseases (unspecified/unidentified)

low

RHS names "a virus" without further detail -- recorded at unspecified level rather than inventing a named virus.

Pests

Glasshouse whitefly

low

Trialeurodes vaporariorum

Named directly by USU.

Aphids

low

Aphididae (various spp.)

Named by both RHS and USU.

What the research guides add

Calendula is a cool-weather annual, and four institutions give consistent timing for it.

• It can be sown directly just before the last frost (Wisconsin), a few weeks before it (Cornell), or in early spring once the soil has reached 60°F and heavy frost has passed (UNH). For earlier flowers, start seed indoors six to eight weeks before the last frost. (Wisconsin Extension, Cornell, UNH Extension)
• Sow thinly under ¼ inch (6 mm) of soil; thin seedlings to 16 inches (40 cm) apart when 1 to 2 inches tall. UNH gives 10 to 15 days to germinate and 30 to 50 days to maturity. (UNH Extension)
• Cornell calls it exceptionally tolerant of cold weather in autumn, and Wisconsin says it blooms almost continuously until the first heavy frost. (Cornell, Wisconsin Extension)
• Deadhead regularly to keep it blooming; sow again every few weeks for fresh plants through the season (Wisconsin). If it languishes in prolonged summer heat, cut it back to encourage autumn flowers (Missouri Botanical Garden). (Wisconsin Extension, Missouri Botanical Garden)
• It grows in any well-drained soil in full sun, and Missouri Botanical Garden suggests some afternoon shade in hot summer climates. (Wisconsin Extension, Missouri Botanical Garden)
• Plants can self-sow, so leave a few to set seed for flowers next season. (UNH Extension)

Calendula in the USA: climate data

Dates are the median 32°F freeze dates and freeze-free days from NOAA NCEI U.S. Climate Normals 1991–2020; zones come from the USDA 2023 Plant Hardiness Zone Map (ZIP code of each city centre).

Sources for this section

• University of Wisconsin–Madison Division of Extension: Calendula, Calendula officinalis
• Cornell University: Flower Growing Guide: Calendula
• University of New Hampshire Extension: How to grow calendula (Calendula officinalis)
• Missouri Botanical Garden: Calendula officinalis (Plant Finder)

Section researched and checked on 24 October 2026 by the SoilCommander Editorial Team. How we check facts: editorial policy.

Sources

1. Utah State University Extension - How to Grow Calendula in Your Garden

   Site/soil: well-drained, moderately nutrient-rich, pH 6-7, tolerates a wide range, suits most Utah soils. Spacing: thin to 8-12in apart in the row. Sowing: 1/4in deep once soil temperature reaches 60°F, germinates in 1-2 weeks; grown from seed or transplants after frost danger passes. Water: 1-1.5in per week in mid-summer for optimal growth, though it can survive low-water conditions. Fertilizing: side-dress every month with a complete soluble fertilizer for optimal bloom. Harvest: pick the complete flower head at full bloom; plants re-bloom in about 2 weeks after deadheading; flowers dry in 1-5 days in a ventilated area away from sunlight. Companion planting: often planted around tomatoes and potatoes to help deter insect pests, acting as a trap crop that draws aphids, whiteflies and thrips with its sticky sap. Pests: whiteflies and aphids, controlled with a hard stream of water or regular insecticidal soap. Diseases: powdery mildew, managed with good air circulation, controlled irrigation, and removing infested plant parts.

These source is specific to this region. The full list of 2 sources behind this guide (Royal Horticultural Society, Utah State University Extension) is in the references of our UK guide to calendulas; they describe the plant itself, which is the same wherever it grows.