Guides

Plain explanations of frost dates and hardiness zones, and what to do with them in the garden. Each guide names the sources it rests on, mostly university extension services and the National Weather Service, and says when it was last checked.

• What your last frost date really means
  A last frost date is a probability, not a deadline. How NOAA works out the dates, why the date most charts print is a coin toss, and which date to plant by.
• Hardiness zones, and what changed on the 2023 map
  What a USDA hardiness zone measures, how it differs from a frost date, what changed when the map was redrawn in 2023, and what to do if your zone moved.
• How to protect plants from a late frost
  What to do when frost is forecast after you've planted: which covers work, how much protection each gives, the watering myth, and what to pick before a fall frost.
• Starting seeds indoors: when and how
  How to time seed starting from your last frost date, crop by crop, and how to grow sturdy seedlings: light, warmth, water, potting up and hardening off.
• What to plant, month by month
  A year in the vegetable garden, counted from your frost dates: what to start indoors, sow and plant out in each stretch of the year, with a real month-by-month example.
• Fall planting: garlic, bulbs and cool-weather crops
  How to time a fall vegetable crop from your first frost date, when to plant garlic, and when spring bulbs like tulips and daffodils go in, north and south.
• Why your frost date can differ from a town 10 miles away
  Weather stations a few miles apart can have last frost dates weeks apart. Real examples from NOAA's data, and the reasons: elevation, cold air pooling, cities and water.
• How long is your growing season?
  Your growing season is the frost-free stretch between your last spring frost and first fall frost. How long it runs across the U.S., how to check a crop will fit, and how to stretch it.

Where to start

If you have never used a frost date before, start with what a last frost date really means. It explains the three dates on every page here, and why the one most charts print is a coin toss rather than a safe planting day. Then look up your own ZIP code on the home page.

If you are planning a whole season, the guides on starting seeds indoors and what to plant month by month walk through the year in order. If a cold night is forecast tonight, go straight to protecting plants from frost.

The guides are general. Your county's extension office knows your soil, your pests and your microclimate, and most offer free advice by phone or email. Our pages tell you which dates to plan around; they can tell you what grows best between them.