When to plant snapdragon in Pittsburgh, Pennsylvania

March 27 – April 10

Transplant outdoors · typical Pittsburgh year

Climate basis: NOAA station Emsworth L/d Ohio Rvr, PA (USC00362574), 6 mi (10 km) from downtown Pittsburgh (ZCTA 15222 centroid), elevation 717 ft, on the 1991–2020 climate normals. Transplant snapdragon outdoors from approximately the dates above, anchored to the median last spring 32°F freeze (April 24). One year in ten still freezes after May 11.

Last spring freezeApril 241-in-10 after May 11

First fall freezeOctober 271-in-10 before Oct 13

Frost-free season≈ 186 daysmedian at 32°F

Hard freeze, 28°Apr 12 – Nov 5kills even hardy greens

USDA zone7a0 to 5°F winter low — not frost timing

The Pittsburgh year

Start seeds indoorsFeb 27 – Mar 13

Transplant outdoorsMar 27 – Apr 10

indoors under lights
in the garden
frost-free season
1-in-10 years still freeze to May 11

Snapdragon in Pittsburgh · freeze context from Emsworth L/d Ohio Rvr, PA, 1991–2020 normals.

Every method, with its sources

Start seeds indoors

Feb 27 – Mar 13

Colorado 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 (Apr 24). Colorado State University Extension

Transplant outdoors

Mar 27 – Apr 10

Illinois 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 (Apr 24). 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.

This week, not a typical year:

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.

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