How Many Plants — Printable 18×24 Wall Chart, Seed Saving Population Sizes by Crop

 The seed saving question nobody answers plainly: how many plants do you need to save from before the variety starts to weaken?

Saving from too few over successive generations causes inbreeding depression — weak, variable, low-yielding crops. The seed looks fine. The problem shows up years later, which is exactly why it is worth having on a wall now.

Six groups, with the population drawn out so the scale is visible rather than numerical. Beans and peas: one plant works, five to ten is better, because they are self-pollinating and naturally inbred. Tomatoes, lettuce and peppers: the same, start here. Squash, melons and cucumbers: five minimum, ten to twenty better. Brassicas: twenty minimum, forty to eighty better, strongly outcrossing and they suffer badly. Carrots, beets and onions: the same numbers, and biennial as well, so it is a two-year commitment. Corn: one hundred minimum, two hundred better — the severe case, and the one people get wrong.

The closing rule: save from across the population, not from the single best plant. Take seed from every plant that meets your standard and mix it. That keeps diversity while you are still selecting.

A single sheet, 18 × 24 inches. Print it at any copy shop, office store or online print service — ask for 18 × 24 on matte or satin paper. You get a print-ready PDF and a PNG.

Adapted from public-domain US government and extension service material, redrawn and set fresh. Not an official publication and not endorsed by any agency. Instant download — print it as many times as you like.