When to plant snapdragon in Louisville, Kentucky
March 3 – March 17
Transplant outdoors · typical Louisville yearClimate basis: NOAA station Louisville Mcalpine, KY (USC00154955), 3 mi (4 km) from downtown Louisville (ZCTA 40202 centroid), elevation 440 ft, on the 1991–2020 climate normals. Transplant snapdragon outdoors from approximately the dates above, anchored to the median last spring 32°F freeze (March 31). One year in ten still freezes after April 14.
The Louisville year
- indoors under lights
- in the garden
- frost-free season
- 1-in-10 years still freeze to Apr 14
Every method, with its sources
Start seeds indoors
Feb 3 – Feb 17Colorado State's seed-starting table lists snapdragon at 8 weeks before the average frost-free date in the 'Indoors' column, the longest lead time of any source found, so indoor sowing opens 8 weeks before the median last freeze and runs a two-week span. Anchored to the median last spring freeze (Mar 31). Colorado State University Extension
Transplant outdoors
Mar 3 – Mar 17Illinois Extension names snapdragon in its hardy-annual list and states those can usually be planted about four weeks before the frost-free date, so transplanting opens 4 weeks before the median last freeze. Anchored to the median last spring freeze (Mar 31). University of Illinois Extension
Variety assumption: Assumes ordinary bedding and cut-flower strains of Antirrhinum majus grown as an annual; it is a hardy annual that flowers best in cool weather and Colorado State's 8-week indoor lead time reflects its slow start from very fine seed.
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 (2)
- Colorado State University Extension: Growing Annual Plants from Seed (accessed 2026-07-25)"Table 1: Starting times for seeds grown indoors and in cold frames, shown as number of weeks to start seed before average frost-free date."
- University of Illinois Extension: Annuals — Flowers (accessed 2026-08-26)The current page names snapdragon as a hardy annual and says hardy annuals can usually be planted about four weeks before the local frost-free date.