Casper, WY Planting Dates — Moon Phase Garden

The four dates that matter

Date	When	What it means
Last spring frost (50%)	May 26	Half of all years see a freeze after this date. It is an average, not a guarantee.
Last spring frost (10%)	Jun 10	Only one year in ten freezes after this. Use it for anything you cannot afford to replant.
First fall frost (50%)	Sep 22	Half of all years freeze before this date. Fall crops are counted back from here.
First fall frost (10%)	Sep 5	An early-freeze year. If a crop must finish, aim to harvest before this.

USDA zone 5a 119 frost-free days Elevation 5338 ft Station Casper Natrona Co Ap

Spring & summer planting in Casper

Dates are calculated from this location's own last-frost date, not from a generic zone chart. “Best moon days” are the days inside each window that fall in the crop's traditional phase — the same rule the app uses.

Crop	Start seed indoors	Plant outdoors	Best moon days	Days to harvest
Strawberry (crowns) transplant	—	Mar 27 – May 5	Apr 1, May 1 Full Moon	perennial — first real harvest next season
Garlic cloves/sets Better planted in fall — see below	—	Apr 9 – May 10	May 2–7 Waning Gibbous	240–300
Asparagus (crowns) transplant	—	Apr 14 – May 19	Apr 23 First Quarter	perennial — first real harvest 2–3 years
Chives either	Mar 31	Apr 14 – May 19	Apr 18–22, May 17 Waxing Crescent	75–90
Onion (from sets/transplants) cloves/sets	—	Apr 14 – May 19	May 2–7 Waning Gibbous	90–120
Peas (English/snap) direct sow	—	Apr 14 – May 19	Apr 23 First Quarter	55–75
Spinach direct sow	—	Apr 14 – May 19	Apr 18–22, May 17 Waxing Crescent	35–50
Cabbage transplant	Mar 24	Apr 21 – May 19	Apr 21–22, May 17–19 Waxing Crescent	65–90
Collards either	Apr 14	Apr 21 – Jun 9	Apr 21–22, May 17–20 Waxing Crescent	55–85
Kale either	Apr 14	Apr 21 – May 26	Apr 21–22, May 17–20 Waxing Crescent	50–65
Lettuce (leaf) either	Apr 21	Apr 21 – Jun 16	Apr 21–22, May 17–20 Waxing Crescent	40–55
Potato cloves/sets	—	Apr 21 – May 26	May 1 Full Moon	70–120
Radish direct sow	—	Apr 21 – Jun 16	May 2–7 Waning Gibbous	22–35
Turnip direct sow	—	Apr 21 – Jun 2	May 2–7 Waning Gibbous	40–60
Broccoli transplant	Mar 24	Apr 26 – May 26	May 17–22 Waxing Crescent	55–80
Brussels Sprouts transplant	Mar 24	Apr 26 – May 26	May 17–22 Waxing Crescent	90–110
Leek transplant	Mar 17	Apr 26 – May 26	May 2–7 Waning Gibbous	100–120
Lettuce (head) transplant	Apr 7	Apr 26 – May 26	May 17–22 Waxing Crescent	60–85
Parsley either	Mar 24	Apr 26 – Jun 2	May 17–22 Waxing Crescent	70–90
Parsnip direct sow	—	Apr 26 – Jun 2	May 1, May 31 Full Moon	100–150
Shallot cloves/sets Better planted in fall — see below	—	Apr 26 – May 26	May 2–7 Waning Gibbous	90–120
Beet direct sow	—	Apr 28 – Jun 16	May 1, May 31 Full Moon	50–65
Kohlrabi either	Apr 14	Apr 28 – Jun 2	May 17–22 Waxing Crescent	45–60
Carrot direct sow	—	May 5 – Jun 16	May 31 Full Moon	65–85
Cauliflower transplant	Mar 24	May 5 – May 26	May 17–22 Waxing Crescent	55–80
Cilantro direct sow	—	May 5 – Jun 16	May 17–22 Waxing Crescent	45–70
Swiss Chard direct sow	—	May 5 – Jun 25	May 17–22 Waxing Crescent	50–60
Dill direct sow	—	May 12 – Jun 25	May 17–22 Waxing Crescent	40–60
Cucumber either	May 5	May 26 – Jun 25	Jun 21 First Quarter	50–70
Green Beans (bush) direct sow	—	May 26 – Jul 10	Jun 21 First Quarter	50–65
Oregano transplant	Mar 31	May 26 – Jun 16	— First Quarter	cut as needed
Sage transplant	Mar 31	May 26 – Jun 16	— First Quarter	cut as needed
Sweet Corn direct sow	—	May 26 – Jul 10	Jun 21 First Quarter	60–100
Thyme transplant	Mar 31	May 26 – Jun 16	— First Quarter	cut as needed
Zucchini / Summer Squash either	May 5	May 26 – Jun 25	Jun 21 First Quarter	45–60
Basil either	Apr 14	Jun 2 – Jun 25	Jun 15–20 Waxing Crescent	30–60
Dry Beans direct sow	—	Jun 2 – Jun 30	Jun 21 First Quarter	85–100
Pole Beans direct sow	—	Jun 2 – Jul 5	Jun 21 First Quarter	60–75
Pumpkin direct sow	May 5	Jun 2 – Jun 30	Jun 21 First Quarter	90–120
Rosemary transplant	May 26	Jun 2 – Jun 25	Jun 21 First Quarter	cut as needed
Tomatillo transplant	Apr 14	Jun 2 – Jun 25	Jun 21 First Quarter	60–75
Tomato transplant	Apr 14	Jun 2 – Jun 25	Jun 21 First Quarter	60–85
Winter Squash direct sow	May 5	Jun 2 – Jun 30	Jun 21 First Quarter	85–110
Cantaloupe / Muskmelon either	May 5	Jun 9 – Jun 30	Jun 21 First Quarter	75–90
Eggplant transplant	Mar 31	Jun 9 – Jun 30	Jun 21 First Quarter	60–90
Okra direct sow	Apr 28	Jun 9 – Jul 5	Jun 21 First Quarter	50–70
Pepper transplant	Mar 31	Jun 9 – Jun 30	Jun 21 First Quarter	60–90
Sweet Potato slips	—	Jun 9 – Jul 5	Jun 30–Jul 5 Waning Gibbous	90–150
Watermelon either	May 5	Jun 9 – Jun 30	Jun 21 First Quarter	70–90

Fall planting in Casper

Fall dates count backward from the first frost, and they add time back for the “fall factor” — days are shortening and cooling, so a crop grows slower than the seed packet promises. Sowing late is the single most common way a fall garden fails.

Crop	Sow or set out	Best moon days	Days to harvest	Hardiness
Cabbage	Jun 9 – Jun 21	Jun 15–20	65–90	hardy
Broccoli	Jun 14 – Jul 1	Jun 15–20	55–80	hardy
Cauliflower	Jun 14 – Jul 1	Jun 15–20	55–80	semi-hardy
Lettuce (head)	Jun 14 – Jun 26	Jun 15–20	60–85	semi-hardy
Peas (English/snap)	Jun 14 – Jul 1	Jun 21	55–75	hardy
Beet	Jun 19 – Jul 6	Jun 29	50–65	semi-hardy
Kale	Jun 19 – Jul 6	Jun 19–20	50–65	hardy
Kohlrabi	Jun 24 – Jul 11	—	45–60	hardy
Cilantro	Jun 29 – Jul 11	—	45–70	semi-hardy
Lettuce (leaf)	Jun 29 – Jul 16	Jul 15–16	40–55	semi-hardy
Turnip	Jun 29 – Jul 16	Jun 30–Jul 5	40–60	hardy
Spinach	Jul 4 – Jul 21	Jul 15–20	35–50	hardy
Dill	Jul 9 – Jul 16	Jul 15–16	40–60	semi-hardy
Radish	Jul 9 – Aug 3	Jul 30–Aug 3	22–35	hardy
Garlic	Aug 23 – Oct 13	Aug 28–Sep 2	240–300	hardy
Shallot	Sep 6 – Oct 7	Sep 27–Oct 2	90–120	hardy

Bottom line: the 50% frost date is a coin flip, not a green light. If you would be sick about losing a flat of tomatoes, plant to the Jun 10 date instead and keep a row cover handy either way.

Where these numbers come from

The frost dates on this page are observed station normals, not estimates: they come from Casper Natrona Co Ap (GHCN USW00024089), one of 6,808 U.S. stations in NOAA's 1991–2020 Climate Normals. The hardiness zone is from the 2023 USDA Plant Hardiness Zone Map. Crop timing is expressed as offsets from your frost dates, drawn from university Extension planting guides.

How precise is any of this?

Extension recommendations for the same crop routinely disagree by two to four weeks, and occasionally more, so these offsets should be presented as windows and starting points rather than deadlines. Three things drive the spread. (1) Regional risk tolerance: for warm-season crops, Colorado State and Utah State put tomatoes, peppers and melons out about 14 days after the last frost, while University of Missouri's calendar works out to roughly 25-35 days after the last frost and University of Maryland's window runs from the frost date itself out to 45 days past it. That is a real 6-week spread for the single most popular garden crop, and it exists because a short-season mountain state is optimizing against a short season while a humid continental state is optimizing against cold, wet spring soil. (2) Soil temperature versus calendar date: most Extension services now say the honest trigger is soil temperature at 4 inches, not the frost date, and the frost-relative number is a convenience translation. A cold, wet spring can push the real date two or three weeks past the calendar recommendation. (3) Days-to-maturity is variety-specific and is measured differently for direct-seeded versus transplanted crops - seed catalogs count from transplant date for tomatoes, peppers, eggplant and cole crops, but from sowing for roots and greens - so a 'days to maturity' range of 60-85 for tomato is genuinely 60-85 depending on which packet you bought. Additionally, the average last frost is a 50% probability, meaning half of all years have a frost after that date; Extension services commonly advise waiting 1-2 weeks past it for anything frost-tender, or being prepared to cover. Treat every number here as plus or minus about 10-14 days.

On the station itself: a weather station is one point. Cities hold their heat, valleys pool cold air, and a garden on a north slope can run two weeks behind one a mile away. Treat this page as your starting point and let your own garden correct it — that is exactly what the journal in the app is for.

Nearby locations

Gillette, WY zone 5a Cheyenne, WY zone 5b Scottsbluff, NE zone 5a Fort Collins, CO zone 5b Rapid City, SD zone 5a Greeley, CO zone 5b

Want this on your phone, in your garden? Moon Phase Garden keeps your frost dates, your planting windows and tonight's moon phase in one place, works offline, and lets you override these dates with what your own garden actually does. Free and ad-free.

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