Butte, Montana Garden Guide: Planting Dates, Frost Dates & Growing Season

Growing Season Snapshot

Butte’s elevation keeps it firmly in the category of bright-sun, short-margin gardening. Days can look encouraging, but the city usually rewards crops that are comfortable with a tighter practical season rather than ones that need long, stable warmth to finish well.

Typical last spring frost June 13

Typical first fall frost September 5

Typical frost-free days 84

GDD left on May 15 (base 50) 1057

These season boundaries are climate normals, not a forecast. A 50% frost date means a 32°F frost arrives by that date in about half of years — and later in about half. Treat these dates as planning anchors, not guarantees.

Butte Planting Calendar

A practical guide to when planting usually works in Butte. These windows are based on climate normals (not a forecast) and line up with the 50% last spring frost and typical early-season heat.

Crop	Planting Window	Method	Best Variety	Local Fit
Cool-season / early window Cold-tolerant crops that usually handle cooler spring conditions better.
Peas	May 16 – May 30	direct sow	Little Marvel	Excellent fit
Spinach	May 16 – May 30	direct sow	Space	Excellent fit
Kale	May 20 – June 9	direct sow / transplant	Winterbor	Excellent fit
Beets	May 23 – June 6	direct sow	Detroit Dark Red	Excellent fit
Carrots	May 23 – June 6	direct sow	Bolero	Excellent fit
Lettuce	May 23 – June 6	direct sow / transplant	Buttercrunch	Excellent fit
Strawberries	May 23 – June 6	plant crowns / transplants	Seascape	Excellent fit
Onions	May 23 – June 6	sets / transplants	Copra	Good fit
Swiss Chard	May 24 – June 13	direct sow / transplant	Bright Lights	Excellent fit
Cabbage	May 30 – June 13	transplant	Stonehead	Excellent fit
Broccoli	May 30 – June 13	transplant	Packman	Strong fit
Cauliflower	May 30 – June 13	transplant	Snow Crown	Strong fit
Potatoes	May 30 – June 13	plant seed potatoes	Kennebec	Strong fit
Main warm-season window Crops that usually do best once frost risk fades and the season starts opening up more fully.
Beans	June 13 – June 27	direct sow	Provider	Borderline
Sweet Corn	June 18 – June 28	direct sow	Yukon Chief	Borderline
Basil	June 22 – July 2	direct sow / transplant	Genovese	Good fit
Cucumbers	June 22 – July 2	direct sow / transplant	Marketmore 76	Good fit
Zucchini	June 22 – July 2	direct sow / transplant	Black Beauty	Good fit
Melons	June 22 – July 2	direct sow / transplant	Minnesota Midget	Risky fit
Pumpkin	June 22 – July 2	direct sow / transplant	Small Sugar	Risky fit
Tomatoes	June 22 – July 2	transplant	Stupice	Risky fit
Watermelons	June 22 – July 2	direct sow / transplant	Sugar Baby	Risky fit
Winter Squash	June 22 – July 2	direct sow / transplant	Delicata	Risky fit
Peppers	June 29 – July 9	transplant	King of the North	Risky fit

How to use this: aim for the earlier part of each window for the most reliable results. Later planting can still work, but it usually depends more on variety maturity, warmer microclimates, and simple protection like row cover or low tunnels.

Common Timing Mistakes

These patterns show up again and again in Butte — especially in typical years.

Starting warm-season crops too late — even small delays can mean they never finish.
Choosing long-season varieties that need more heat than a typical year provides.
Relying on calendar dates instead of crop maturity and typical frost timing.

Missed Your Planting Window? What Can You Still Grow?

This table shows what can still mature from several later-season planting dates in Butte. It compares the growing degree days still typically available after each checkpoint with the heat each crop usually needs to finish, then applies a 15% safety margin to separate crops that usually still fit from ones that are more borderline.

Usually fits Borderline Too tight

Crop	Heat Units	May 15	Jun 1	Jul 1	Aug 1
Spinach	450 (base 40)	✅	✅	✅	✅
Lettuce	500 (base 40)	✅	✅	✅	✅
Strawberry	600 (base 40)	✅	✅	✅	✅
Pea	600 (base 40)	✅	✅	✅	✅
Beet	650 (base 40)	✅	✅	✅	✅
Basil	700 (base 50)	✅	✅	✅	❌
Kale	700 (base 40)	✅	✅	✅	✅
Zucchini	750 (base 50)	✅	✅	⚠️	❌
Carrot	750 (base 40)	✅	✅	✅	✅
Swiss chard	750 (base 40)	✅	✅	✅	✅
Cucumber	800 (base 50)	✅	✅	⚠️	❌
Broccoli	900 (base 40)	✅	✅	✅	✅
Bean	900 (base 50)	⚠️	⚠️	❌	❌
Cabbage	1000 (base 40)	✅	✅	✅	⚠️
Cauliflower	1000 (base 40)	✅	✅	✅	⚠️
Sweet corn	1100 (base 50)	❌	❌	❌	❌
Potato	1100 (base 45)	✅	✅	✅	❌
Melon	1200 (base 50)	❌	❌	❌	❌
Tomato	1200 (base 50)	❌	❌	❌	❌
Pepper	1300 (base 50)	❌	❌	❌	❌
Onion	1300 (base 45)	✅	✅	⚠️	❌
Winter squash	1300 (base 50)	❌	❌	❌	❌
Pumpkin	1300 (base 50)	❌	❌	❌	❌
Watermelon	1350 (base 50)	❌	❌	❌	❌

Climate normals GDD planning

Compare your season’s typical heat accumulation against crop requirements before first fall frost.

Heat matters more than calendar days Use this when crop maturity depends on warmth, not just frost-free days. Especially useful for warm-season crops and short-season locations.

Best for borderline crops Especially useful for warm-season crops and short-season locations.

Check Crop Maturity and Timing in Butte

Enter a ZIP / Postal Code in Butte and your planting date to see whether different crops can typically mature before first fall frost.

ZIP / Postal

Crops

Select one or more crops.

Select Outdoor sow / Transplant date

How the Growing Season Works in Butte

Butte is a short-season growing environment. The season closes quickly enough that variety maturity, planting timing, and early establishment usually matter more than small differences in calendar timing.

Warm-season crops: usually perform best when they are established promptly after the last spring frost.
Variety maturity matters: shorter-season cultivars are often the safer choice than longer-season bets.
Protection can help: row cover, transplants, and sheltered spots often improve consistency in a short season.

Remaining Season Heat in Butte (Base 50 GDD)

Growing Degree Days (Base 50°F) measure heat accumulation. “Remaining GDD” shows how much usable heat is typically still available from a given date onward in a normal season.

Planting date	Base	Typical GDD still available
May 15	50	1057
June 1	50	1048
July 1	50	882
August 1	50	461

Use these values to judge whether a crop or variety still has enough heat left after planting. This is especially helpful for later sowings, shorter-maturity choices, and deciding whether a second round is realistic.

How Gardeners Adapt

Experienced gardeners in Butte usually adjust their timing and crop choices to match how the season actually behaves, not just the calendar.

Starting warm-season crops indoors to gain extra time early in the season.
Choosing short-season or faster-maturing varieties whenever possible.
Using row cover or low tunnels to smooth out temperature swings early and late in the season.
Succession planting fast crops to keep beds productive through summer.
Watching local conditions closely and adjusting timing year by year.

Butte Garden Planning Chart

A practical “typical year” for planning. Use it as a baseline, then adjust for microclimates and variety maturity.

Stage	What it usually means
Early season	Start cold-tolerant crops, prep beds, and pay more attention to soil warmth and night temperatures than to the calendar alone.
Main planting	Around June 13, the main planting push usually begins as frost risk fades. Warm-season crops generally perform best when they get established promptly.
Peak growth	This is when water, fertility, spacing, and pest pressure have the biggest effect on final yield.
Late-summer decisions	Second plantings can work, but success usually depends on maturity, microclimate, and how warm late summer stays.
Finish window	Plan to have frost-sensitive crops mostly wrapped up by September 5. Cooling nights often slow crops before the first real frost arrives.

Typical season length: 84 frost-free days between the median spring and fall frost dates.

Crop Guides for Butte

Published crop-specific planting guides for Butte, ordered from best fit to highest risk.

Excellent fit

Beets

Beets are usually one of the easier crops to grow here.

When to Plant Beets in Butte

Cabbage

Butte usually gives cabbage enough season that maturity is rarely the hard part.

When to Plant Cabbage in Butte

Carrots

Carrots perform easily here in a typical year.

When to Plant Carrots in Butte

Kale

This crop usually has enough season here that maturity is rarely the hard part.

When to Plant Kale in Butte

Lettuce

Very early to mid-season varieties usually fit comfortably here.

When to Plant Lettuce in Butte

Peas

Peas are usually one of the easier crops to grow here.

When to Plant Peas in Butte

Spinach

Butte usually gives spinach enough season that maturity is rarely the hard part.

When to Plant Spinach in Butte

Strawberries

Strawberries perform easily here in a typical year.

When to Plant Strawberries in Butte

Swiss Chard

This crop usually has enough season here that maturity is rarely the hard part.

When to Plant Swiss Chard in Butte

Strong fit

Broccoli

Broccoli is usually a dependable crop choice here.

When to Plant Broccoli in Butte

Cauliflower

Butte usually gives cauliflower enough season for reliable maturity.

When to Plant Cauliflower in Butte

Potatoes

Potatoes perform well here when planted on time.

When to Plant Potatoes in Butte

Good fit

Basil

Basil is usually a practical crop here with good timing.

When to Plant Basil in Butte

Cucumbers

Cucumbers generally works well here when gardeners stay on schedule.

When to Plant Cucumbers in Butte

Onions

Butte usually gives onions enough season, but not much room for sloppy timing.

When to Plant Onions in Butte

Zucchini

This crop fits here, though slower choices still carry more risk.

When to Plant Zucchini in Butte

Borderline

Beans

Beans can work here, but timing and variety choice matter a lot.

When to Plant Beans in Butte

Sweet Corn

Butte can support sweet corn, though the margin is not generous.

When to Plant Sweet Corn in Butte

Risky fit

Melons

Melons are harder to finish well here and usually needs the fastest approach.

When to Plant Melons in Butte

Peppers

Butte usually gives peppers a narrow margin for maturity.

When to Plant Peppers in Butte

Pumpkin

This is a higher-risk crop here unless the site and timing are especially favorable.

When to Plant Pumpkin in Butte

Tomatoes

Growers usually do best with quick varieties and the warmest spots they have.

When to Plant Tomatoes in Butte

Watermelons

Very early varieties usually have the best chance here.

When to Plant Watermelons in Butte

Winter Squash

Winter squash is harder to finish well here and usually needs the fastest approach.

When to Plant Winter Squash in Butte

Looking for broader guidance? See planting timing across Montana

Butte, Montana Garden Guide: Planting Dates, Frost Dates and Growing Season