Last year, I made the mistake of sleeping on September. I’d been so focused on summer stone fruit and tomato Pilgrimage that I almost missed what might be Colorado’s most generous week — that narrow window when the markets overflow with summer’s last burst and fall’s first arrivals, all stacked side by side on the same folding tables. I showed up to the Union Station Farmers Market on a random Saturday in late September and found peaches, peppers, dry-farmed tomatoes, and the first butternut squash of the season sitting together like old friends. That cooler, I went home with more than I could possibly eat. And I’ve been planning my September visits ever since.
Here’s the honest truth about Colorado produce seasons: they’re short, they’re strange, and they’re deeply affected by our unpredictable altitude and weather patterns. But September is the exception. It’s the month when everything hits at once — when the risk of early frost has mostly passed but the crispness of true fall hasn’t yet arrived. If you’re serious about eating locally in Colorado, September is your month. Here’s why, and exactly how to take advantage of it.
What Makes September Different
Summer in Colorado is almost too easy. The markets are packed, the peaches are abundant, and everyone tells you to eat local. But September has a different character. The crowds thin out after Labor Day, which means the farmers who showed up every Saturday in July are suddenly showing up with the best stuff — because they’re not rushed, and they actually have time to talk about their season.
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At its core, September is a transition month in Colorado’s high-altitude growing zones. We’re working with a shorter season than most of the country — Denver sits at 5,280 feet, and many of our best farms are even higher. That means our peak harvest window compresses differently than it does in California or the Midwest. When the first cool nights arrive in September (usually sometime mid-month), it triggers a kind of accelerated maturity in crops like winter squash, peppers, and late tomatoes. The plants sense the shift and pour everything into final fruit production.
The result is a two-to-three week period where multiple growing seasons converge. This is the secret season.
The Holy Trinity of Late Summer
If you take nothing else from this article, remember these three crops that hit their absolute peak in Colorado during September:
Tomatoes — This is counterintuitive because we associate tomatoes with summer. But in Colorado’s high-altitude environment, September often delivers better tomato quality than August. The cooler nights concentrate sugars, and the plants are less stressed than during July’s intense heat waves. Look for dry-farmed varieties at the Union Station market or the Cherry Creek Fresh Market on Wednesday afternoons. Cherry tomatoes, especially the Sungolds and Black Cherries, are particularly outstanding right now.
Peppers — This is Colorado’s hidden gem. New Mexico chile season technically starts in August, but the best roasting happens in mid-to-late September when the heat units have fully accumulated. The Santa Fe-style green chiles from farms like those in the Rio Grande watershed areas and Pueblo growers reach their peak complexity in September. If you’ve never had a freshly roasted Colorado green chile, you’re missing one of the region’s defining food experiences.
Winter Squash — The first butternut and acorn squash arrive in late September, typically a week or two ahead of what most people expect. This is when I stock up. A good farm stand in Boulder or along the Pea Boulevard corridor will have varieties you won’t find at any grocery store — delicata from Red Wagon Farm, spaghetti squash from Miller’s Farm in Erie, and occasionally more unusual varieties like Long Island Cheese or Carnival squash.
Where to Actually Shop
Let me cut through the romance of farmers markets and give you some practical geography. The Saturday Union Station market is the obvious choice and it’s genuinely excellent, but it’s also crowded and parking is a nightmare. If you’re trying to maximize value and reduce stress, consider the Wednesday Cherry Creek Fresh Market or the Saturday Boulder Farmers Market on 13th Street, which runs through mid-October.
For the truly dedicated, the smaller farm stands scattered along the northern Front Range offer a different experience. places like the Cornell Farms stand near Westminster or the Oxford Farms operation in Lafayette operate on their own schedules but reward the effort. I drove out to the Boulder Valley Ranch area last September and found heirloom apples at a family operation that I don’t think has a website. That’s the kind of discovery September makes possible.
One underutilized resource: the Colorado Department of Agriculture’s Colorado Proud program maintains a searchable database of local farms and producers. It’s not glamorous, but it works.
What to Skip This Month
I want to be honest with you, because I think honest is more useful than enthusiastic. There are things September is not, and knowing the difference matters.
Skip the impulse buying at chain grocery store “local” sections. September produce displays at places like King Soopers and Safeway often use “Colorado Grown” signage loosely. The apples might be from the Western Slope, but the tomatoes were likely shipped from Mexico and simply relabeled. When you see a display claiming local provenance at a major chain, ask someone. Most employees don’t actually know the supply chain details, which tells you something.
Skip the “late season” asparagus and strawberries. Some farms artificially extend these seasons with greenhouse production. It’s technically local, but the flavor and price-to-quality ratio is terrible. Asparagus and strawberry season in Colorado is June through early July. Respect that cycle.
Skip overripe heirloom tomatoes if you’re not planning to eat them within 24 hours. September heirlooms are often bred for character over shelf stability. That gorgeous Cherokee Purple you’re eyeing at the stand? It’s probably at peak today and will be mealy by Tuesday. Buy for immediate use, not for the week ahead.
A Practical Shopping Strategy
Here’s what I actually do in September. I go early — by 8 AM on Saturday at Union Station — and I make one lap before buying anything. I identify what looks exceptional that week, then I buy only what I can use within three days. I bring multiple bags (cloth, ideally), a cooler in my car, and cash (some vendors still prefer it, and small farms appreciate avoiding card processing fees).
I also bring a list but I let the market override it. If something is staggeringly good that week — those Sungolds, that first butternut — I buy too much and I deal with the abundance by making sauce, roasting, or sharing. September abundance is meant to be captured and preserved. That brings me to the most important part.
Preserving September
You cannot talk about September in Colorado without talking about preservation. The reason September matters isn’t just that the produce is good this month — it’s that it’s good right now, and that window closes. A first frost in late September can devastate tender crops overnight. I learned this the hard way in 2024 when an early October freeze ended my tomato season two weeks before I was ready.
So when you find something exceptional, buy extra. Roasted green chiles freeze beautifully and will taste like summer in January. Overripe tomatoes become sauce or can be frozen whole. Peppers can be roasted and frozen in vacuum-sealed bags. The Growing Gardens program in Boulder offers canning classes throughout September — they’re worth attending if you’ve never preserved before.
The Bottom Line
Colorado’s secret season isn’t really a secret once you understand the timing. September is when our local food system delivers its most diverse, highest-quality, most affordable produce of the entire year — and when the weather is perfect for getting out to experience it. The markets are less crowded than August, the farmers are more relaxed, and the product speaks for itself.
My advice: don’t let another September pass without experiencing it properly. Pick a Saturday, arrive early, bring good bags, and buy more tomatoes than you think you need. You’ll figure out what to do with the rest. You always do, in September.