When to plant celosia in Philadelphia, Pennsylvania

March 30 – April 13

Transplant outdoors · typical Philadelphia year

Climate basis: NOAA station Phila Franklin Inst, PA (USC00366886), 1 mi (1 km) from downtown Philadelphia (ZCTA 19107 centroid), elevation 60 ft, on the 1991–2020 climate normals. Transplant celosia outdoors from approximately the dates above, anchored to the median last spring 32°F freeze (March 30). One year in ten still freezes after April 12.

Last spring freezeMarch 301-in-10 after Apr 12

First fall freezeNovember 171-in-10 before Nov 4

Frost-free season≈ 232 daysmedian at 32°F

Hard freeze, 28°Mar 17 – Nov 29kills even hardy greens

USDA zone7b5 to 10°F winter low — not frost timing

The Philadelphia year

Start seeds indoorsMar 2 – Mar 16

Transplant outdoorsMar 30 – Apr 13

Direct-sow outdoorsMar 30 – Apr 13

indoors under lights
in the garden
frost-free season
1-in-10 years still freeze to Apr 12

Celosia in Philadelphia · freeze context from Phila Franklin Inst, PA, 1991–2020 normals.

Every method, with its sources

Start seeds indoors

Mar 2 – Mar 16

University of Maryland's celosia production guide states seed is sown 4 weeks before the last frost date, which is the only frost-anchored figure found (Minnesota's 10-weeks guidance is anchored to the outdoor planting date, not to frost, so it cannot be used), giving a two-week sowing span opening 4 weeks before the median last freeze. Anchored to the median last spring freeze (Mar 30). University of Maryland Extension · University of Minnesota Extension · University of Illinois Extension

Transplant outdoors

Mar 30 – Apr 13

University of Maryland says to sow or transplant celosia in the field after the danger of frost has passed, so the window opens at the median last freeze; note Maryland's stricter companion rule of night temperatures consistently above 65 to 70 degrees F is not frost-anchored and cannot be expressed here, so the window's opening day is optimistic in cool-summer areas. Anchored to the median last spring freeze (Mar 30). University of Maryland Extension · University of Minnesota Extension · University of Illinois Extension

Direct-sow outdoors

Mar 30 – Apr 13

The same University of Maryland sentence covers direct sowing — sow or transplant celosia in the field after the danger of frost has passed — so direct sowing opens at the median last freeze, with Illinois independently classing celosia a tender annual. Anchored to the median last spring freeze (Mar 30). University of Maryland Extension · University of Minnesota Extension · University of Illinois Extension

Variety assumption: Assumes Celosia argentea in its crested (cockscomb) and plumed forms; Maryland warns that exposure below 60 degrees F stunts plants and triggers premature flowering, so the frost-anchored window opens earlier than the temperature at which celosia actually thrives.

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 (3)

University of Maryland Extension: Production of Celosia as a Cut Flower (accessed 2026-07-25)
"Sow Celosia 4 weeks before the last frost date."
University of Minnesota Extension: Celosia (accessed 2026-07-25)
"Celosia seeds can be started indoors about 10 weeks prior to the anticipated outdoor planting date."
University of Illinois Extension: Celosia — Flowers (accessed 2026-07-25)
"Tender Annual"

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