Practical planning tools for short growing seasons.
Climate-based broccoli planting guide for Montrose, Colorado
When to Plant Broccoli in Montrose
Broccoli is usually straightforward to fit into the season in Montrose. Gardeners typically get more value from steady growth and timing than from worrying about whether the crop will finish.
Typical Planting Window
Excellent fit in this climate
Use the planting dates below for broccoli in Montrose.
Start indoors
April 1
Typical planting windowMay 6 – May 20
MethodTransplant
Typical days to maturity60–75
Broccoli is usually started indoors around April 1 and planted outdoors during the normal local window of May 6 to May 20.
Most varieties need about 60–75 days to reach maturity once they are in the garden.
Broccoli is usually easy to fit into the season in Montrose, and the real payoff is having enough room to size the crop properly and harvest at the stage you actually want.
The climate usually makes this crop possible without strain, but the difference between an average result and a strong one still comes from steady growth and harvesting at the right stage.
Best local strategy:
Take advantage of the margin by managing for even sizing and a clean finish, not by getting casual about timing.
Can Broccoli Mature in Montrose?
Growing degree days measure how much useful warmth typically accumulates during the season. For broccoli, this helps estimate whether local heat accumulation is usually enough for the crop to reach maturity on time.
Available GDD (base 40)2777
Typical crop GDD target900
Heat margin+1877
From the usual planting window, Montrose typically provides about 2777 growing degree days for broccoli. With a typical crop target of 900, that leaves a heat margin of +1877. That large heat margin means the crop usually has no trouble reaching maturity here. In practice, planting timing mostly affects how comfortably the crop sizes up and when harvest is ready, not whether the crop can finish.
When Is It Too Late to Plant?
If planting later than usual, this table shows how much growing degree day heat is still available from each point in the season. For broccoli, it is most useful for judging how much freedom you still have to plant for quality, finish, and harvest goals as the season moves along.
Checkpoint
Remaining GDD
Heat margin
Fit vs typical target
Apr 15
3008
+2108
Comfortable
May 1
2980
+2080
Comfortable
May 15
2886
+1986
Comfortable
Jun 1
2681
+1781
Comfortable
Jun 15
2440
+1540
Comfortable
Jul 1
2090
+1190
Comfortable
How Different Broccoli Varieties Affect Results
The season in Montrose usually supports most broccoli varieties comfortably, which means the more useful decision is what kind of crop you want rather than simply how fast it finishes.
Varieties that often fit well here include:
De Cicco
— an early broccoli often chosen where gardeners want flexibility and quicker harvest
Packman
— a dependable standard with good short-season practicality
Green Magic
— a strong early hybrid that often handles the main spring window well
Belstar
— productive and reliable where the season gives a reasonable cool-weather runway
Marathon
— more exposed if spring is delayed or summer heat arrives early
Best Broccoli Varieties for Montrose
Broccoli variety choice in Montrose is mostly about head reliability, side-shoot production, stress tolerance, and how cleanly the crop fits the cool part of the season.
May 20
local season starts
October 1
frost pressure returns
Less heat used2777 GDD available
Hover or tap the dots to see which recommended varieties use that much local heat.
For Montrose, start with Packman and Green Magic for broccoli when you want dependable early broccoli heads or strong early hybrid broccoli.
Choose De Cicco when you want flexible early broccoli and side shoots.
Look at Marathon and Belstar when you specifically want later broccoli plantings or reliable main-season broccoli.
Compare each variety’s heat need and maturity timing against the local frost-free window before choosing what to grow.
Recommended starting point
PackmanEarly
850 GDD needed2777 available before frost
May 20October 1
Comfortable fit
Why this fit?
Local season fit:
Packman leaves about 1927 GDD cushion against the normal Montrose crop heat estimate.
Best for: dependable early heads.
A practical early broccoli with good short-season usefulness.
Tradeoff: Practical more than specialty.
Green MagicEarly
850 GDD needed2777 available before frost
May 20October 1
Comfortable fit
Why this fit?
Local season fit:
Green Magic leaves about 1927 GDD cushion against the normal Montrose crop heat estimate.
Best for: strong early hybrids.
A strong early hybrid that often handles the main spring broccoli window well.
Tradeoff: Still needs cool growing conditions to finish well.
Fastest / most cushion
De CiccoVery early
750 GDD needed2777 available before frost
May 20October 1
Comfortable fit
Why this fit?
Local season fit:
De Cicco leaves about 2027 GDD cushion against the normal Montrose crop heat estimate.
Best for: flexible early broccoli.
An early broccoli that is useful when gardeners want flexibility, side shoots, and a quicker harvest path.
Tradeoff: Heads may be less uniform than hybrid types.
Also realistic
MarathonLate
1050 GDD needed2777 available before frost
May 20October 1
Comfortable fit
Why this fit?
Local season fit:
Marathon leaves about 1727 GDD cushion against the normal Montrose crop heat estimate.
Best for: later broccoli plantings.
A slower broccoli that is more exposed if spring is delayed or summer heat arrives early.
Tradeoff: More exposed if spring is delayed or summer heat arrives early.
BelstarMid-season
950 GDD needed2777 available before frost
May 20October 1
Comfortable fit
Why this fit?
Local season fit:
Belstar leaves about 1827 GDD cushion against the normal Montrose crop heat estimate.
Best for: reliable main-season broccoli.
A productive broccoli that works well where the season gives a reasonable cool-weather runway.
Tradeoff: Needs more cool-season runway than early broccoli.
GDD comparisons are a planning shortcut, not a guarantee. Soil, watering, sowing depth, pests, transplant quality, and harvest goals still affect the final result.
Variety class
Typical days to maturity
Typical GDD need
Local fit
Very early
55–60
750
Good fit
Early
60–68
850
Good fit
Mid-season
68–78
950
Good fit
Late
78–90
1050
Good fit
Main risk: When this crop disappoints here, the problem is usually practical rather than climatic. Timing, steady growth, and harvest stage matter more than season length.
How Frost Affects Planting Dates for Broccoli in Montrose
Montrose usually has about 134 frost-free days, with a typical last spring frost around May 20 and a typical first fall frost around October 1.
Typical last spring frostMay 20
Typical first fall frostOctober 1
Typical frost-free days134
Minimum safe temperature28°F /
-2
°C
Broccoli is generally
lightly frost tolerant
and temperatures below about 28°F (
-2
°C) can slow growth or damage plants.
Broccoli is usually tolerant enough of cool conditions that light frost is not the main concern. The more useful question is how early planting affects establishment and overall crop quality.
When this crop disappoints in Montrose, the issue is usually management rather than climate fit. Timing, consistency, and harvest decisions matter more than season length.
In Montrose, the local season usually gives broccoli plenty of breathing room when planting happens around May 13. For a better local margin, gardeners usually do best in south-facing walls, sheltered gardens, raised beds, and sunnier urban lots. Cooler spots like low spots, exposed sites, and shadier yards often make timing tighter. For broccoli, the best local sites often help the crop get moving earlier and make timing a little more forgiving.
Set up broccoli for steady growth and pest protection
The better results usually come from steady growth, pest protection, and avoiding early setbacks.
Transplant support
Strong young plants help avoid slow starts and uneven sizing.
