City Gardening Guides

Why a city page beats a state page

A state’s climate summary is an average across everything inside its borders, and for a gardener that average is often the least useful number available. 24 metro areas are covered here, and the reason each one gets its own page is that large cities routinely sit in a different hardiness zone, or carry different frost dates, from the rural areas that dominate the state figure.

Three effects do most of the work. The urban heat island is the largest: a dense city holds heat in pavement and buildings, which raises winter minimums and pushes the first fall frost later, so a downtown garden can be a meaningful fraction of a zone warmer than a field forty miles out. Elevation pulls the other way and is the dominant variable in the Mountain West, where a metro sitting in a valley floor is warmer than the foothills around it and every thousand feet of climb shortens the season. Water and coastline moderate both directions — a large lake or an ocean delays spring warming and delays autumn cooling, which lengthens the frost-free window while making late-spring cold snaps less predictable.

What each city guide contains

Every city page works from the same structure: the USDA hardiness zone range for the metro, the typical last spring frost and first fall freeze, the resulting frost-free window, and a printable planting calendar with the crops that fit that window. Where a metro spans more than one zone — which is common for cities built across a river valley or up a hillside — the page shows the range rather than a single figure, because a single number would be wrong for a large share of readers inside the same city.

The dates are “typical” figures derived from long-term climate normals, not a forecast, and that distinction is the most important thing to carry into the page. A typical last frost date is a midpoint: roughly half of years see a later one. That is why the planting calendar is written against the frost window rather than a single day, and why the safe approach in a year with a cold spring is to treat the calendar as a sequence to shift later rather than as a schedule to follow exactly. Check a ten-day forecast before you transplant anything tender.

City page, or ZIP lookup?

Use a city page when you want the context — what grows well in this metro, how its season compares with the state, and a printable plan to work from. Use the ZIP lookup when you want your own numbers: it converts a specific ZIP into a zone and frost-date pair, which is more precise than any metro-level figure because a ZIP is a much smaller area. The two are complementary, and the city pages link to the ZIP tool for exactly that reason.

If your city is not listed, the ZIP lookup will still give you accurate zone and frost dates, and the state guides cover the broader regional picture including the grass types and pest pressure that apply across the state. Every city page also links to those, so nothing here is a dead end.