Year-Round Greenhouse Growing: What to Plant in Every Season
The biggest misconception about greenhouses is that they're only for summer. They're not. A greenhouse extends your growing season in both directions — and with the right approach, you can harvest something fresh every single month of the year.
Here's exactly what to grow and when.
Spring (March–May)
Spring is when the greenhouse earns its value most obviously. While outdoor gardeners are still watching frost forecasts, you're already harvesting.
Best crops for spring: lettuce, spinach, radishes, peas, parsley, and chives. These cool-season crops actually prefer temperatures between 45–65°F — exactly what a greenhouse provides in early spring.
Start lettuce and spinach in mid-March. You'll have harvestable leaves by mid-April, a full month before it's safe to plant outdoors in most of the US.
Late spring and summer (May–August)
Once your greenhouse consistently stays above 60°F at night, it's time for warm-season crops. Tomatoes, peppers, cucumbers, and basil are the summer stars.
Plant tomato seedlings in late May. By mid-July you'll be harvesting — and wondering why you ever bought grocery store tomatoes. The flavor difference is dramatic.
Summer greenhouse management is mostly about keeping things cool enough. Open vents aggressively. Consider shade cloth on very hot days. The plants will tell you when they're stressed — wilting in the afternoon heat is normal, but if they're not recovering by morning, they need more airflow.
Fall (September–October)
Fall is many greenhouse gardeners' favorite season. The intense summer heat is gone, light is still decent, and cool-season crops are at their best.
In late August, while your tomatoes and cucumbers are still producing, plant a second round of lettuce, spinach, kale, and radishes. They'll be ready to harvest in September and October — and the flavor is noticeably sweeter than spring crops.
Winter (November–February)
An unheated greenhouse tracks outdoor temperatures closely, typically running 5–10°F warmer on sunny days. This is enough for hardy crops like kale, mâche, and spinach in mild-winter climates.
In cold climates (Zone 5 and below), a small electric space heater — even running just overnight — keeps temperatures above freezing and extends your growing season significantly.
Microgreens are the secret weapon of winter greenhouse gardening. They grow fast, need minimal space, and provide genuine nutritional density when outdoor produce is at its worst.
The math
For a Zone 6 gardener, an outdoor season runs roughly mid-May to early October — about 4.5 months. Add a greenhouse and your cool-season growing extends from mid-March to mid-November. That's 8 months instead of 4.5. You've nearly doubled your season without a single heater.
Ready to extend your growing season? Browse our greenhouses here.