When to plant marigold in Knoxville, Tennessee
April 11 – April 25
Transplant outdoors · typical Knoxville yearClimate basis: NOAA station Knoxville Exp Stn, TN (USC00404946), 5 mi (8 km) from downtown Knoxville (ZCTA 37902 centroid), elevation 830 ft, on the 1991–2020 climate normals. Transplant marigold outdoors from approximately the dates above, anchored to the median last spring 32°F freeze (April 11). One year in ten still freezes after April 29.
The Knoxville year
- indoors under lights
- in the garden
- frost-free season
- 1-in-10 years still freeze to Apr 29
Every method, with its sources
Start seeds indoors
Feb 14 – Feb 28Sources disagree on indoor timing - UW-Madison says about 8 weeks and UMN about 10 weeks before the after-frost outdoor planting date - and the later, more conservative 8-week start wins, giving 56 to 42 days before last frost. Anchored to the median last spring freeze (Apr 11). University of Wisconsin-Madison Division of Extension · University of Minnesota Extension · Iowa State University Extension and Outreach
Transplant outdoors
Apr 11 – Apr 25UMN, UW-Madison and Iowa State all agree that marigold plants go out once danger of frost has passed, so the set-out window opens at the last-frost date and runs two weeks. Anchored to the median last spring freeze (Apr 11). Iowa State University Extension and Outreach
Direct-sow outdoors
Apr 11 – Apr 25Iowa State University Extension is the only one of the three sources to anchor direct seeding to frost rather than soil temperature ('Sow marigold seeds outdoors when the danger of frost is past'), giving a two-week window from the last-frost date; UW-Madison's and UMN's 65F soil-temperature rules cannot be frost-anchored and were not encoded. Anchored to the median last spring freeze (Apr 11). University of Wisconsin-Madison Division of Extension · University of Minnesota Extension · Iowa State University Extension and Outreach
Variety assumption: Covers Tagetes marigolds (French, African/American and signet types) only; pot marigold / calendula (Calendula officinalis) is a different plant and is not encoded here.
These windows describe typical years (1991–2020 climate normals), not this year's forecast. Freezes happen outside them — especially in frost pockets, valleys, and urban edges. Watch the forecast before committing tender plants.
Crop rule sources (3)
- University of Wisconsin-Madison Division of Extension: Marigolds - Wisconsin Horticulture (accessed 2026-07-25)"Marigolds can be direct seeded into garden soil when soil temperatures are >65°F or seeds can be started indoors ~8 weeks prior to transplanting outdoors after the threat of frost has passed."
- University of Minnesota Extension: Marigolds (accessed 2026-07-25)"Marigold seeds can be started indoors about 10 weeks prior to the anticipated outdoor planting date."
- Iowa State University Extension and Outreach: When can I plant marigolds outdoors? | Yard and Garden (accessed 2026-07-25)"Plant marigold seedlings outdoors after the danger of frost is past."