About Garden Plot

Garden Plot is a set of free garden planning tools for US gardeners: a square-foot garden planner, planting calendars and frost dates for every ZIP code, and guides to 55 vegetables, herbs and flowers. There is no account, no trial and no paywall, and your plans stay in your browser.

Where the numbers come from

• Frost dates: NOAA National Centers for Environmental Information, U.S. Climate Normals 1991–2020. For each ZIP code we use the nearest of 7,305 weather stations with freeze statistics, measured from the ZIP code’s center. Dates can differ in hilly, coastal or urban spots, so we show the station and its distance.
• Spring warm-up: from the same normals, the date each station’s average daily temperature reaches 50, 55, 60 and 65°F. Warm-season crops such as tomatoes, beans and squash wait for it as well as for the last frost.
• Hardiness zones: 2023 USDA Plant Hardiness Zone Map, USDA Agricultural Research Service and PRISM Climate Group, Oregon State University. ZIP code lookups are approximate and this is not the official USDA map; see planthardiness.ars.usda.gov.
• Planting windows and spacing: land-grant university extension planting guides, chiefly Vegetable Planting Guide (GardenNotes #720) (Colorado State University Extension). Square-foot densities follow the standard square-foot gardening method.

How we grade companion planting

Much companion planting advice is folklore repeated from chart to chart. We grade every pairing as research-backed, mixed evidence, practical reason or tradition only, and say why. Our main references:

• Gardening with Companion Plants (EM128E), Linda Chalker-Scott, Washington State University Extension, 2023
• Marigolds (Tagetes spp.) for Nematode Management (ENY-056), Krueger, Dover, McSorley & Wang, University of Florida IFAS Extension
• Trap Cropping, Washington State University Extension Master Gardener Program
• Brassica flea beetles, UMass Amherst Vegetable Program
• Trap cropping: a review of the state of the art, Sarkar et al., 2018 (open-access review)
• Food Yields and Nutrient Analyses of the Three Sisters, Jane Mt. Pleasant, Ethnobiology Letters 7(1), 2016
• Vegetable Planting Guide (GardenNotes #720), Colorado State University Extension