Moving somewhere to garden? What to check first

Most gardeners look up one number before they move: the hardiness zone. It matters, but it’s only a winter number. It tells you how cold the coldest night of an average year gets. It says nothing about summer heat, rain or the soil you’ll actually dig. Here is the order to check them in.

Step 1: The zone, and what it leaves out

A USDA hardiness zone is based on the average coldest winter temperature. Each zone covers 10 degrees Fahrenheit, split into a and b halves of 5 degrees. The current map came out in November 2023, built from 1991 to 2020 weather data. About half the country moved into the next warmer half zone.

USDA itself is careful about what the map can’t show. Summer heat, rain, soil and wind all affect whether a plant survives. So do small local spots: a warm wall facing south, a frost pocket at the bottom of a hill.

The hardiness layer starts with every zone switched on. Narrow it to the range your plants need. Our planting zones page explains the map in more detail.

Step 2: Summer heat

Plenty of plants that survive a mild winter fail in a long, hot summer. The American Horticultural Society made a heat zone map for exactly that in 1997. It counts the days above 86 degrees Fahrenheit in a typical year, in 12 zones. It hasn’t been updated since, so treat it as a rough guide.

Step 3: Frost dates and rain

Your growing season runs from the last spring frost to the first fall frost. NOAA publishes average dates from the same 1991 to 2020 records. It warns that any single year can be far off the average, so plant with some margin.

Rain decides how much watering you’ll do. The rainy days layer shows how many days a year get measurable rain, county by county. Like hardiness, it starts wide open, so set the range you want.

Step 4: The soil under the lawn

This is the one gardeners skip. Older neighborhoods can have lead in the soil, from old paint and from decades of traffic. The EPA recommends testing soil before you grow food in it. County health departments and university extension labs do the tests.

The EPA’s current guidance by result is simple. Below about 200 parts per million, good habits are enough: gloves, and washing hands and produce. Between 200 and 400, grow food in raised beds filled with clean soil. Above 400, don’t use the existing soil for food at all.

The soil contamination layer leaves out areas near known contaminated sites, like Superfund sites, leaking fuel tanks, brownfields and plants that report toxic releases. It can’t test your yard, but it shows where a test matters most.

Step 5: Space and sun

No map shows which way a backyard faces or how much shade the neighbor’s oak throws. Visit at midday, and again late in the afternoon. A vegetable garden wants six or more hours of sun.

Then ask a local nursery what actually thrives in town. They’ll know the local frost pockets and pests that no map shows.

Your starting map

This map opens with hardiness, rainy days and soil contamination switched on. Narrow the hardiness and rain ranges to what you want to grow.