Planting Calendar by ZIP / Zone

How to use the planting calendar

A planting calendar answers one simple question: what should I be sowing, starting or transplanting right now? The answer depends almost entirely on two things — your USDA hardiness zone and the month. Your zone tells you roughly when your last spring frost and first autumn frost fall, and those two dates frame your whole growing season. Everything in this tool is built from those zone averages, so the lists it shows are planning windows, not promises for a specific garden on a specific day.

Start by entering your ZIP code and choosing your state. The ZIP code is a rough locator, not a zone detector: USDA zones follow climate, elevation and local geography, and a single ZIP code can straddle a zone boundary — a sheltered valley garden and an exposed hilltop a mile apart can sit in different zones. That is why the tool asks you to pick your zone from your state's range instead of pretending the ZIP code alone is enough. If you are not sure of your zone, the USDA Plant Hardiness Zone Map lets you look it up by address, and your local cooperative extension service can confirm it — both are free, and both are more reliable than any calculator.

What the four lists mean

Start seeds indoors lists the crops whose indoor sowing window falls in the month you picked. Tender crops such as tomatoes and peppers are usually started six to eight weeks before the average last frost; hardy crops such as lettuce and peas need only four to six weeks. Starting indoors buys you a longer season, but seedlings started too early grow leggy on a windowsill and transplant poorly, so the window matters more than the head start.

Sow outdoors is for direct sowing into the soil. Hardy crops can go out four to six weeks before the last frost — peas, spinach and radishes actually prefer cool soil. Tender crops wait until the last frost has passed and the soil has warmed. Sowing a tender crop into cold, wet soil is the most common beginner mistake: the seed rots instead of sprouting, and a second sowing two weeks later usually overtakes the first.

Transplant seedlings out is the move-out date for plants you started indoors. Harden them off first — a week of gradually longer spells outside, brought in at night — or the shock of sun, wind and cold nights can set them back by weeks.Ready to harvest is an estimate from days to maturity, counted from the usual sowing window. Taste and size are better guides than the calendar: a tomato is ready when it is fully coloured and slightly soft, not when a date arrives.

Why frost dates are ranges, not dates

Every frost date in this tool is an average, and averages hide a lot. A “last frost April 1–15” means that over many years, the last spring frost in that zone has typically fallen somewhere in that range — in any given year it can come earlier or later, sometimes by two weeks or more. Gardeners who plant tender crops on the average date lose plants about half the time; waiting a week or two past the average, and watching the forecast, is the practical way to use it. Keep row cover or an old sheet handy for the first few weeks after transplanting — a single cold night can undo a month of indoor growing. The same logic applies in autumn: the first frost range tells you when to expect the season to end, so count backwards from it when you sow autumn crops such as kale and spinach.

Practical tips

Work in small, regular sowings rather than one big one. A row of lettuce sown every two weeks gives you salad all season; a single sowing gives you a glut, then nothing. Keep a notebook of what you sowed and when — after one season you will have a calendar tuned to your actual garden, which beats any zone average. Water seeds gently and keep the soil damp until germination; a dry crust is enough to kill a whole row. And remember that this calendar covers the crops in our database — flowers and less common vegetables follow the same rules (hardy versus tender, weeks before or after last frost), so you can apply the same logic with the seed packet as your guide.

Related tools: try the Garden Planner for a month-by-month planting list, the Frost Date Calculator for your zone's frost ranges and season length, and the Seed-Starting Calculator to work out exact indoor sowing dates. For the bigger picture, browse the planting calendar hub and your state gardening guide.