When to plant Swiss chard in Oklahoma

In spring, from Feb 15 – May 15 in Ardmore to Apr 1 – June 15 in Guymon.

In fall, June 1 – Sept 10.

USDA's earliest safe spring and latest safe fall planting dates, matched to each place's average frost dates.

Swiss chard planting dates by place in Oklahoma
PlaceSpringFall
AdaMar 1 – May 25June 1 – Sept 10
AltusMar 15 – June 15June 1 – Sept 10
ArdmoreFeb 15 – May 15June 1 – Sept 15
BartlesvilleMar 15 – June 15June 1 – Aug 1
BethanyMar 1 – May 25June 1 – Sept 10
BixbyMar 1 – May 25June 1 – Sept 10
Broken ArrowMar 1 – May 25June 1 – Sept 10
ChickashaMar 1 – May 25June 1 – Sept 10
ChoctawMar 1 – May 25June 1 – Sept 15
ClaremoreMar 15 – June 15June 1 – Sept 10
CowetaMar 1 – May 25June 1 – Sept 10
Del CityMar 1 – May 25June 1 – Sept 15
DuncanFeb 20 – May 15June 1 – Sept 15
DurantMar 1 – May 25June 1 – Sept 15
EdmondMar 15 – June 15June 1 – Sept 10
El RenoMar 15 – June 15June 1 – Sept 10
Elk CityMar 15 – June 15June 1 – Sept 10
EnidMar 15 – June 15June 1 – Sept 10
GlenpoolMar 1 – May 25June 1 – Sept 10
GuthrieMar 1 – May 25June 1 – Sept 10
GuymonApr 1 – June 15June 1 – Aug 1
JenksMar 1 – May 25June 1 – Sept 10
LawtonMar 1 – May 25June 1 – Sept 15
McAlesterMar 1 – May 25June 1 – Sept 10
MiamiMar 15 – June 15June 1 – Sept 10
Midwest CityMar 1 – May 25June 1 – Sept 15
MooreMar 1 – May 25June 1 – Sept 15
MuskogeeMar 15 – June 15June 1 – Sept 10
MustangMar 1 – May 25June 1 – Sept 10
NewcastleMar 1 – May 25June 1 – Sept 15
NormanMar 1 – May 25June 1 – Sept 10
Oklahoma CityMar 1 – May 25June 1 – Sept 10
OkmulgeeMar 15 – June 15June 1 – Sept 10
OwassoMar 1 – May 25June 1 – Sept 10
Ponca CityMar 15 – June 15June 1 – Sept 10
Sand SpringsMar 1 – May 25June 1 – Sept 10
SapulpaMar 1 – May 25June 1 – Sept 10
ShawneeMar 1 – May 25June 1 – Sept 15
StillwaterMar 15 – June 15June 1 – Sept 10
TahlequahMar 1 – May 25June 1 – Sept 10
TulsaMar 1 – May 25June 1 – Sept 10
Warr AcresMar 1 – May 25June 1 – Sept 10
WeatherfordMar 1 – May 25June 1 – Sept 10
WoodwardMar 15 – June 15June 1 – Sept 10
YukonMar 1 – May 25June 1 – Sept 10

Planting dates: USDA Home and Garden Bulletin No. 9 (1967), tables 4 and 5. Frost dates: NOAA U.S. Climate Normals 1991–2020. The full USDA table for swiss chard.