Wyoming · zones 4a–5a
When to plant tomatoes in Wyoming.
Sow or transplant between Jun 4 to Jun 22 in a typical year, keyed to Wyoming's median last frost around May 28. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Tomatoes dates for a typical Wyoming season.
1 · Start indoors
Apr 23 to May 11
About 6 weeks before set-out. Warm spot, real light.
2 · Set out
Jun 4 to Jun 22
Keyed to the ~May 28 last frost. Sow 0.25" deep, 24" apart.
Harvest
~73 days later
~12 lb per plant over ~8 weeks.
Wyoming spans more than one climate: Zone 5 is the most common zone, but the state runs 4a to 5a. That's why the planner works from your ZIP code's frost dates, not your zone: mountain and coastal gardens in the same state can be three weeks apart.
In Wyoming: watch for
The pests that find tomatoes here.
The short season here, about 112 frost-free days, keeps tomato, slicing in front of tomato hornworm only briefly. One early row cover usually carries a planting through the worst of it.
Big green caterpillars strip leaves and leave black droppings.
Organic fix: Handpick at dusk; spray Bt on the young ones.
Clusters on new growth, sticky leaves, curling tips.
Organic fix: Blast with water, then insecticidal soap or neem.
Dark spots with concentric rings, starting on the lowest, oldest leaves.
Organic fix: Remove affected leaves, mulch to stop soil splash, space for airflow.
Greasy, water-soaked blotches in cool, wet spells. No rings, and not bottom-up.
Organic fix: Pull infected plants fast, keep leaves dry, use neem as a preventive.
Septoria leaf spot
Many small tan spots with dark brown edges, low leaves first, no rings inside.
Organic fix: Strip the lowest leaves, mulch against soil splash, stake for airflow.
Your season math: Wyoming gives tomatoes about 112 frost-free days, and it needs roughly 73 days to a first harvest. It's a one-planting crop, so time that single sowing well.
Planting tomatoes in Wyoming: questions
When should I plant tomatoes in Wyoming?+
In a typical Wyoming year, sow tomatoes or set out transplants between Jun 4 to Jun 22, keyed to the state's median last frost around May 28. Your exact dates shift with your ZIP code and microclimate.
When do I start tomatoes seeds indoors in Wyoming?+
Start seeds inside about 6 weeks before set-out: roughly Apr 23 to May 11 for a typical Wyoming season.
What USDA zone is Wyoming?+
Wyoming spans zones 4a–5a, mostly zone 5. But frost dates, not zones, set planting time. The free planner uses your ZIP code's actual frost dates.
How many tomatoes plants do I need?+
Depends who you're feeding. The crop page has exact counts per household size, or the free planner does the math for your family in about 60 seconds.