I had a customer email me last February with a photo. Snow piled up outside, grey skies, dead everything — and she's holding a bowl of salad she just picked from her greenhouse. Lettuce, spinach, some arugula. Nothing fancy. But it was February in Ohio and she grew it herself.

That's the thing about year-round growing. It's not complicated or magical. It's just understanding what grows when, and letting your greenhouse do what it's designed to do.

First, let's kill some myths

You're not going to grow tomatoes in January. I mean, you could, but you'd spend more on heating than those tomatoes are worth. When people talk about "year-round growing," they don't mean growing summer crops in winter. They mean always having something growing, something to harvest, every month of the year.

January might be lettuce and kale. July is tomatoes and peppers. October could be both — late tomatoes still hanging on while your winter greens get established. The greenhouse doesn't eliminate seasons. It stretches them, overlaps them, and fills the gaps.

What I actually harvest each month

I'll share what works for me in zone 6. Adjust earlier or later depending on where you live.

January and February are the slow months. Not much is growing fast, but I'm still picking. Spinach planted back in September is still producing leaves. Same with kale — it actually tastes sweeter after frost. I've got mâche (corn salad) that handles cold better than anything else I've grown. And herbs. Parsley doesn't care about cold. Neither does chives once it's established.

March is when things wake up. Days are getting longer and the greenhouse warms up faster. I start tomato and pepper seeds inside the house under lights, but the greenhouse is already producing. Lettuce planted in late winter is ready. I direct-seed more greens because they'll grow faster now.

April and May, I'm transplanting. Tomato seedlings go into the greenhouse while my neighbors are still waiting for their last frost date. The soil is warm, the days are long, and those plants take off. I'm also harvesting the last of the winter greens before they bolt in the warming temperatures.

June through August is abundance. More tomatoes than we can eat. Cucumbers reproducing like rabbits. Peppers finally hitting their stride. The challenge isn't growing — it's keeping up with the harvest and keeping the greenhouse from overheating.

September, I'm doing two things at once. Still harvesting summer crops, but also planting for winter. Lettuce seeds go in. Spinach. Asian greens like bok choy and tatsoi. These need time to establish before the days get really short.

October and November, the summer crops finally give up. But by now the winter crops are ready to take over. And because they're in the greenhouse instead of outside, they keep growing instead of getting killed by frost.

December brings us full circle. Growth slows down a lot — short days mean less photosynthesis — but I'm still picking. Fresh greens for Thanksgiving, for Christmas, for random Tuesday dinners when it's dark at 5pm and everything outside is frozen.

That's year-round growing. It's not one continuous crop. It's a relay race where you're always handing off to the next thing.

The temperature thing isn't that complicated

People overthink this.

Summer: open the vents. Seriously, that's most of it. Greenhouses get hot — over 100°F on a sunny day if you're not careful. Our greenhouses have roof vents and I open them pretty much every morning from May through September. On really hot days, I open the doors too. Moving air keeps plants happy.

If you're not home during the day, get automatic vent openers. They're like $30, they don't need electricity, and they save your plants from cooking. A wax cylinder expands when it gets hot and pushes the vent open. Simple and it works.

Winter: the greenhouse does most of the work. Twin-wall polycarbonate holds heat way better than you'd expect. On a sunny January day, even when it's 25°F outside, my greenhouse hits 50-60°F inside. The panels hold onto that warmth for hours after sunset.

For the coldest nights, I have a small electric heater with a thermostat set to 35°F. It kicks on maybe a few hours on the worst nights. My electric bill goes up maybe $20-30 in the coldest months. Not nothing, but not crazy either.

Some people use water for thermal mass instead. Fill some black containers with water, put them against the north wall. They absorb heat during the day and release it slowly at night. Works well if you'd rather not deal with electricity.

Cold-hardy crops can handle a lot. Lettuce survives down to about 28°F. Spinach and kale can take even lower — I've seen kale bounce back from temperatures in the low 20s. You're not trying to keep your greenhouse tropical. You're just trying to keep it above the point where cell walls freeze and burst.

What grows best in cold weather

Not everything likes winter. Tomatoes, peppers, cucumbers, beans — they want warmth. Below 50°F they sulk. Below 40°F they start dying. Don't bother with them in winter unless you're willing to heat seriously.

But plenty of crops actually prefer cool weather. They bolt and turn bitter in summer heat, but they're perfectly happy in a 40°F greenhouse.

Lettuce is the obvious one. It germinates in cool soil, grows steadily in cool air, and stays sweet instead of turning bitter. Butterhead, romaine, leaf lettuce — they all work.

Spinach is even tougher than lettuce. It handles colder temperatures and actually tastes better after a light frost. Something about the cold converts starches to sugars.

Kale is nearly indestructible. I've seen it survive single-digit temperatures under row cover inside the greenhouse. And like spinach, frost makes it sweeter.

Asian greens are underrated for winter growing. Bok choy, tatsoi, mizuna, mustard greens — they grow fast, handle cold well, and add variety when you're getting tired of lettuce and spinach.

Mâche (corn salad) is my secret weapon for the coldest months. It's slow-growing but handles cold better than almost anything. When everything else struggles in December and January, mâche keeps producing.

Herbs worth trying: parsley (incredibly cold-hardy), chives (goes dormant but survives), cilantro (actually prefers cool weather — it bolts immediately in summer), and mint (will survive almost anything).

The part nobody talks about: light

Temperature gets all the attention, but light matters just as much. Maybe more.

In December, you might have 9 hours of daylight. In June, you have 15. That's a huge difference for plants that need light to photosynthesize and grow.

This is why winter growth is slow even when temperatures are fine. A lettuce that takes 45 days to mature in April might take 70 days in December. Not because it's cold, but because there's less light.

There's not much you can do about this without adding grow lights, which most home gardeners don't want to deal with. The practical approach is to adjust your expectations. Winter is for slow, steady harvest — not summer-level abundance. Plant more than you think you need because each plant produces less.

One trick: time your planting so crops are nearly mature before the shortest days hit. If you plant spinach in late September, it's mostly grown by early December. Then you're just harvesting through winter, not asking it to do heavy growing in low light.

Zone matters more than anything

Everything I've said needs adjusting based on where you live.

If you're in zone 8 or higher — places like the Pacific Northwest, parts of the South, coastal California — winter is easy mode. You might not even need heat. Your problem is summer, not winter. You'll be managing excessive heat more than cold.

Zones 6-7 cover a lot of people. Cold winters but not brutal. This is where greenhouse growing really shines. A few months of supplemental heat, smart crop selection, and you're harvesting year-round without massive effort.

Zones 4-5 mean real winter. You can absolutely grow year-round, but you'll need more heat or you'll focus mainly on the shoulder seasons — extending fall and starting spring early. Winter production is possible but takes more attention.

Zone 3 and below, you're in serious cold. The greenhouse is still valuable — it might take your effective growing season from 3 months to 6 or 7. But true winter growing requires real heating infrastructure or acceptance that some months you're just keeping the greenhouse from collapsing under snow.

The greenhouse you choose matters

I'll be direct here because it matters for year-round growing specifically.

Cheap greenhouses with thin plastic covering are almost useless in winter. Single-layer plastic has zero insulation value. All that heat you collect during the day disappears within an hour of sunset. You'll spend a fortune on heating or just give up on winter growing entirely.

The twin-wall polycarbonate on our greenhouses makes a real difference. Two layers of material with an air gap between them — that's actual insulation. I've measured 30°F differences between inside and outside on sunny winter days, and the panels hold heat for hours after dark.

Frame strength matters too. Snow loads get heavy. Wind in winter can be brutal. If you're planning to use your greenhouse 12 months a year, make sure it's built to survive 12 months a year.

→ Our Premium Polycarbonate Greenhouse handles 65 mph wind and 3 feet of snow. The arch roof sheds snow naturally: https://gardeningculture.com/products/polycarbonate-greenhouse-kit

→ The Heavy-Duty Greenhouse Kit has the same tough specs in a traditional peaked-roof style: https://gardeningculture.com/products/heavy-duty-greenhouse-kit

Starting out

If this is your first year, don't try to master everything at once.

Start simple: use the greenhouse to start seeds early in spring. Keep your summer crops going as long as possible in fall. Plant one or two cold-hardy things in late summer and see what happens in winter.

Pay attention to your specific greenhouse. How warm does it get on sunny days? How quickly does it cool off at night? What temperature does it bottom out at on the coldest nights? Every greenhouse is a little different based on size, location, and what's around it.

After a year, you'll know your greenhouse. You'll know when to plant, what works, what doesn't. Year two gets easier. By year three, you'll be the person sending photos of January salads to jealous friends.

Going deeper

→ New to greenhouses? Start with our beginner guide: https://gardeningculture.com/blogs/growing-guides/greenhouse-for-beginners

→ Want to know how to pick the right greenhouse? Read the buying guide: https://gardeningculture.com/blogs/growing-guides/greenhouse-buying-guide

→ Quick questions? Check the FAQ: https://gardeningculture.com/pages/faq

→ Specific questions about year-round growing? Email hello@gardeningculture.com — I talk about this stuff all the time.

→ Ready to start? Browse our greenhouses: https://gardeningculture.com/collections/polycarbonate-greenhouses