Garden planner

Frost dates — pick a nearby city for its average last spring and first fall freeze (NOAA’s 1991–2020 normals for the station named), as the typical (median) date or the safer one (a 10 % chance of a later spring or earlier fall freeze), and the season’s year. Or type your own dates. A fall date before the spring one is read as the next year, so southern-hemisphere seasons work.

Sowing calendar — add crops. For each, the windows to start seeds indoors, transplant, sow outdoors (some crops have an early and a late sowing), sow or plant again for fall, and the approximate harvest, drawn on a year chart with your frost dates (Calendar full screen for a bigger view) and listed in a table. Windows are counted in weeks from your frost dates after Cornell Cooperative Extension’s planting guide; fall sowings count back from the first fall frost by the days to maturity plus two weeks, as that guide advises. Successions: sow again every so many days (set per crop) — cool-season crops pause six weeks after the last frost and resume for fall; warm crops continue while they can still mature before the frost. Add to my calendar downloads the lot as an .ics file.

Beds — square-foot beds of any size (1 ft or 30 cm squares, north at the top). Pick a crop from the palette and tap or drag over squares. Each bed counts the plants (the usual square-foot counts: 1 tomato, 4 lettuces, 9 beets, 16 carrots a square; vines over several squares) and lists hints for neighbouring squares, for a family grown there last year (rotation), and for tall crops shading shorter ones.

Companions — every hint, sorted by evidence: evidence (research or plain plant pathology), mixed (works sometimes, or only under conditions) and folklore (traditional, without good evidence — harmless to try).

Print the plan opens a clean page with the frost dates, the calendar table and the beds. Your plan is saved in this browser; Export and Import move it as JSON.

Sources: Cornell Cooperative Extension of Rockland County, Vegetable Planting Guide (Hort 52, 2011) — sowing windows and days to maturity; NOAA NCEI, U.S. Climate Normals 1991–2020 — freeze-date probabilities; Mel Bartholomew, All New Square Foot Gardening — plants per square (a rule of thumb); S. Uvah and T. H. Coaker (1984) on onions and carrot fly; University of California research on sweet alyssum and lettuce aphids.

Related: sun and moon (day length and the sun’s path over your garden), energy usage analyser, heat loss.

Frost dates and the season travel in a readable link; a shared link also carries the crop list and beds. Add the tab after #: frost, calendar, beds or companions.