Home / Guides / Regional Calendars, Climate & Data
Regional Calendars, Climate & DataRegional Crop Suitability Calendar
A crop suitability calendar asks one question first: does this crop fit your climate at all. Only then does it ask when to plant.
Key points
- Suitability depends on season length, heat, winter cold and water.
- Hardiness zones apply to winter survival of perennials, not planting dates.
- Compare days to maturity or degree day needs with local records and risk dates.
- Trial small before committing acreage.
What does crop suitability mean?
A crop is suitable when your climate gives it enough time, enough heat, tolerable cold, and enough water at the right times. If one factor falls short, you need either a different variety, season extension, irrigation, or a different crop.
Suitability is not the same as possibility. Many crops can be coaxed through a season in marginal conditions, but the cost in covers, labor and risk may not pay.
A useful test is to ask what you would have to add to make the crop work: covers, irrigation, a shorter variety, a hoop house. If the list is long and each item costs real money, the crop is probably not suited to your site even if it can technically be grown.
Which four climate factors should you check?
First, season length between the last spring freeze and the first fall freeze at the threshold your crop tolerates. Second, heat accumulation, often expressed as growing degree days. Third, winter minimum temperature for perennials, which is what the USDA Plant Hardiness Zone Map describes. Fourth, water: rainfall timing and irrigation access.
Remember that hardiness zones do not give frost dates or planting dates, so use them only for winter survival of perennial crops.
Write each factor as a yes, no or marginal for every crop on your list. Crops with several marginal marks need a plan for covers, irrigation or variety choice, and crops with a no are better left for another site.
- Season length at the right threshold
- Heat accumulation
- Winter minimum for perennials
- Water supply and timing
How do you compare a crop to your climate?
Find the crop's days to maturity or growing degree day requirement in an extension variety guide, then compare it with your local record. For example, if a variety needs more heat than your site typically provides before your fall risk date, an earlier variety or a different crop is the safer choice.
Look at the extremes too. Heat can cut yield during bloom for some crops, and cold nights can slow warm-season crops even above freezing.
Be honest about market and labor, too. A crop that fits the climate but needs picking in the same weeks as your busiest crop may not fit your operation.
How do regions differ in what they suit?
Cool coastal areas often favor root crops, brassicas, lettuce, potatoes and beans, according to Oregon State Extension, while heat-loving crops need shorter-season varieties and warming aids. Southern regions with long seasons may have room for a second planting, and University of Georgia Extension publishes guidance on planting a second vegetable crop in the same season. Northern regions are limited by season length and favor earlier varieties and cold-hardy crops.
These are broad patterns. Your valley, hillside and soil can sit outside them.
Local extension variety trials are the best evidence for your region, so read their results for the crops you are considering.
How do you build the calendar?
Create a grid with crops down the side and months across the top. For each crop, mark the months when soil and air temperature fit its needs, using your local frost probabilities and soil temperature checks. Shade the months that depend on protection or irrigation differently from those that do not.
Add a column for market timing, because a crop that fits the climate may still miss the window when buyers want it.
Variety choice often matters more than crop choice. Within one crop, extension trials commonly show large differences in days to maturity, cold tolerance and disease resistance, so look for results from your own state.
How do you test suitability before committing?
Trial a small block for a season or two. Record planting dates, stand, stress events, harvest timing and sales. Compare with extension trial results for your area and ask local growers what has failed, not just what has worked.
A small trial costs little. A failed field of an unsuited crop costs a lot.
What records help you refine suitability over time?
Keep a short sheet for every crop you try: planting date, variety, days to harvest, stress events, marketable yield and what you would change. Add the weather notes that explain the outcome, such as a late freeze or a hot spell during bloom.
After three or four seasons you will have a suitability record that is specific to your farm. Share it with your extension office, which can compare it with trial data and with what other growers nearby are seeing.
Sources and further reading
Last reviewed: November 2026. Educational information, ranges only. Confirm timing with your county extension office.