How to Grow Signet Marigolds UK | Regional Planting Calendar

Signet Marigold (Tagetes tenuifolia)

A field of flowering signet marigold plants — “Tagetes tenuifolia 1 (aka)” by André Karwath aka Aka is licensed under CC BY-SA 2.5. Source: Wikimedia Commons

2 sources cited · Verified

The short answer

Plant
Early March to late March
Site
6+ hours of sun, soil pH 6–7.5
Biggest risk
Grey mould

In the UK, signet marigolds go in the ground early March to late March.

Signet marigolds (Tagetes tenuifolia) — Annual, USDA zones 2-11, UK hardiness zone 3 (PFAF).

Timing is the decision that matters most in the UK: sowing early March, and that same window applies across all 4 regions covered here.

Core growing advice on this page is checked against named horticultural sources — see References.

Regional Planting Calendar

Region Sow
Southern England early March to late March
Midlands early March to late March
Northern England early March to late March
Scotland early March to late March
Southern England - detail & sources

PFAF states seed is sown in a greenhouse in March, with seedlings transplanted out after the last expected frost; applied as one UK-wide indoor-sowing window across all four sub-regions.

Midlands - detail & sources

PFAF states seed is sown in a greenhouse in March, with seedlings transplanted out after the last expected frost; applied as one UK-wide indoor-sowing window across all four sub-regions.

Northern England - detail & sources

PFAF states seed is sown in a greenhouse in March, with seedlings transplanted out after the last expected frost; applied as one UK-wide indoor-sowing window across all four sub-regions.

Scotland - detail & sources

PFAF states seed is sown in a greenhouse in March, with seedlings transplanted out after the last expected frost; applied as one UK-wide indoor-sowing window across all four sub-regions.

Quick Facts

A field of flowering signet marigold plants — “Tagetes tenuifolia 1 (aka)” by André Karwath aka Aka is licensed under CC BY-SA 2.5. Source: Wikimedia Commons
“Tagetes tenuifolia 1 (aka)” by André Karwath aka Aka is licensed under CC BY-SA 2.5. Source: Wikimedia Commons.
Factor Value
Soil pH 6 - 7.5
Sunlight 6-8 hours direct sun
Germination temp 18C
Soil texture Light (sandy), medium (loamy) or heavy (clay) (PFAF)
Drainage Well-drained, though tolerant of heavy clay (PFAF)
Lifecycle Annual, USDA zones 2-11, UK hardiness zone 3 (PFAF); RHS describes the genus habit as annuals or perennials with upright growth.
Edible parts flowers

At a Glance

Red and orange bicolor signet marigold flowers — “Tagetes tenuifolia 002” by Amada44 is licensed under CC BY 3.0. Source: Wikimedia Commons
“Tagetes tenuifolia 002” by Amada44 is licensed under CC BY 3.0. Source: Wikimedia Commons.
Tagetes tenuifolia Signet Marigold Grey mould Slugs Snails DISEASES PESTS

Soil & Growing Conditions

A dense mass planting of yellow signet marigold flowers — “Kääpiösamettikukkia (7885385144)” by Dodo from Finland is licensed under CC BY 2.0. Source: Wikimedia Commons
“Kääpiösamettikukkia (7885385144)” by Dodo from Finland is licensed under CC BY 2.0. Source: Wikimedia Commons.

Water: Tolerates both dry and moist soil once established (PFAF)

Soil pH range

6 7.5

Span reflects genuine variation between the cited authorities, not a single agreed figure.

Growth Stages

A young signet marigold plant with one flower — “Signet marigold BFRI” by Tanvir Anjum Adib is licensed under CC BY-SA 4.0. Source: Wikimedia Commons
“Signet marigold BFRI” by Tanvir Anjum Adib is licensed under CC BY-SA 4.0. Source: Wikimedia Commons.
Stage BBCH Notes
Sowing and establishment 0 Sow seed in a greenhouse in March, only just covering the seed; germination typically occurs within about 2 weeks. Transplant seedlings out after the last expected frost (PFAF).
Vegetative growth 3 Compact, upright growth to about 0.8m tall and wide; needs full sun and tolerates both dry and moist soil once established (PFAF). The bruised foliage is strongly aromatic.
Flowering 6 Showy, daisy-like single or double flower-heads through summer and autumn (RHS). Deadhead regularly to prolong flowering and petal production for the kitchen.
Harvest 8 Petals are picked and used fresh, scattered over salads or as a garnish for their citrus-like flavour (RHS; PFAF).

Harvest & Storage

Close-up of a single orange signet marigold flower — “Tagetes tenuifolia 2021-09-07 1356” by Salicyna is licensed under CC BY-SA 4.0. Source: Wikimedia Commons
“Tagetes tenuifolia 2021-09-07 1356” by Salicyna is licensed under CC BY-SA 4.0. Source: Wikimedia Commons.

When to pick: Pick individual petals or whole flower-heads once open; the petals have a pleasant citrus-like flavour and are used sparingly as a flavouring or garnish in salads, sandwiches and wine (PFAF). Deadheading spent flowers both supplies more petals and extends the flowering season (PFAF).

Diseases

Signet marigold stem and leaf detail — “Tagetes tenuifolia 2021-09-07 1360” by Salicyna is licensed under CC BY-SA 4.0. Source: Wikimedia Commons
“Tagetes tenuifolia 2021-09-07 1360” by Salicyna is licensed under CC BY-SA 4.0. Source: Wikimedia Commons.
Fuzzy grey-brown Botrytis mould covering a tomato stem — Rasbak, CC BY-SA 3.0
Rasbak, CC BY-SA 3.0
Grey mould
low

Botrytis cinerea

Soft brown fruit decay; Fuzzy grey-brown mould

PFAF names botrytis (grey mould) as a disease risk this species is prone to.

Pests

A pinnately divided, ferny signet marigold leaf — “Tagetes tenuifolia 2021-09-07 1358” by Salicyna is licensed under CC BY-SA 4.0. Source: Wikimedia Commons
“Tagetes tenuifolia 2021-09-07 1358” by Salicyna is licensed under CC BY-SA 4.0. Source: Wikimedia Commons.
Slugs
low

Gastropoda (slugs, various spp.)

Named directly by PFAF as a pest this species is prone to.

Snails
low

Gastropoda (snails, various spp.)

Named directly by PFAF as a pest this species is prone to.

References

  1. Annual, USDA zones 2-11, UK hardy zone 3. Height/spread 0.8m. Soil: light/medium/heavy, well-drained but tolerates heavy clay, pH mildly acid/neutral/mildly alkaline. Full sun, tolerates dry and moist soil. Propagation: sow March in greenhouse, just cover seed, germinates within 2 weeks, transplant after last frost. Pests: slugs, snails, botrytis. Native to Central/South America (Mexico to Guatemala). Edible: flowers, citrus-like flavour, used sparingly as garnish/flavouring. Root secretions insecticidal against nematodes and some slugs. Produces yellow dye from flowers. Dynamic accumulator plant. Aromatic bruised foliage.

  2. Annuals or perennials, upright growth, strongly aromatic pinnately divided leaves, daisy-like single or double flower-heads in summer and autumn. Family Asteraceae, not native to GB/Ireland. Page carries limited further growing detail (no soil/sun/hardiness/pest data provided).

2 independent sources are cited for this crop. Where they disagree - soil pH is the clearest case - every figure is preserved rather than averaged into false precision.

Frequently Asked Questions

When should I sow signet marigolds in the UK?

In Southern England, from early March. In Scotland, wait until early March. Treat these as a guide rather than a fixed date — the governing rule is to sow only once frost risk has passed and temperatures are reliably warm enough.

When do I sow signet marigolds?

Sow early March to late March, at around 18°C for germination.

What soil pH do signet marigolds need?

A pH of about 6–7.5. That span reflects genuine variation between the authorities we cite rather than a single agreed figure — the References section lists each source's exact range.

What problems affect signet marigolds?

Our data links 1 disease and 2 pests to this crop. See the sections above for each one and how to manage it.

Plan next season before the problems start

Most of the advice on this page comes down to timing and spacing — sowing at the right moment, rotating beds, and giving plants enough airflow. The UK Garden Planner lays your plot out month by month so those decisions are already made before the season starts.

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Last verified 2026-09-03