Disclaimer

Plant counts are estimates

The seed spacing calculator gives you a planning estimate based on Mel Bartholomew's All New Square Foot Gardening densities, Johnny's Selected Seeds row spacing data, and the Old Farmer's Almanac reference material. It is not a guarantee. Actual plant count and yield vary with:

• Your climate zone and microclimate (a south-facing wall vs an open field)
• Soil health: organic matter, drainage, pH, microbiome
• The specific variety you chose (a determinate Roma tomato needs far less room than an indeterminate Brandywine)
• Weather, a late freeze or early heatwave can erase a whole planting
• Seed freshness, viability drops about 10-20% per year in storage
• Pollinator populations in your yard (huge factor for squash, cucumbers, and corn)

Use the calculator's numbers as a starting point. Adjust down 10-20% for your first season in a new bed; adjust up once you know how your soil and climate behave.

Not a substitute for local expertise

Your local cooperative extension office publishes planting calendars, soil test recommendations, pest advisories, and variety trials specific to your region. Use them. No general-purpose calculator (including this one) knows that your county had a verticillium outbreak last summer, or that the Japanese beetle hatch is running 10 days early, or that your soil pH is stuck at 5.4 and nothing's going to grow well until you lime.

Variety specifics matter

"Tomato" is a species. "Cherokee Purple" is a cultivar. The calculator uses species-level densities. Determinate varieties (Roma, Celebrity, Mountain Fresh) tolerate tighter spacing. Indeterminate varieties (Brandywine, Black Krim, Cherokee Purple) want more room and better trellising. Same for winter squash: Delicata vs Blue Hubbard is a 3x difference in bed space. Read the specific variety's description before planting.

Food safety

Anything you eat from your own garden is your responsibility. Wash produce thoroughly. If you use compost, let it finish properly (at least 6 months, or pile temps above 130 degrees F for a week). Never use pet manure or fresh manure on edible beds. When in doubt, the USDA FSIS has food safety guidelines for home-grown produce.

Affiliate links

Some links on this site may be affiliate links, meaning we earn a small commission if you buy through them at no cost to you. We only recommend products we'd use ourselves. Current affiliates include Johnny's Selected Seeds, Burpee, and True Leaf Market.

Accuracy

We do our best to keep formulas and species data accurate and up to date. Density figures come from published references that themselves get updated as new agronomic research comes out. If you spot an error, let us know.