How Many Vegetable Plants Do I Need?

Work back from what you eat

Not forward from the space you happen to have.

Sowing to fill a bed is how gardens end up with forty lettuces maturing in the same fortnight and nothing to eat by September. Starting from consumption gives you a number that means something — and if the space won't hold it, that's a genuine finding you can act on rather than a disappointment you discover in July.

The number nobody can give you

Yield you expect per plant is the input this whole calculation turns on, and the range is enormous.

It moves with the crop, the variety, the soil, the season, the spacing, how much you water and feed, and whether the plant picks up a disease in August. Two gardens on the same street get different answers from the same packet.

Catalogues sometimes quote a figure and extension services sometimes publish one. Both are starting points, not predictions.

Your own record beats all of them. Weigh what one crop actually produced, once, divide by the number of plants, and you have a figure that describes your soil and your gardening. That's why the printable's yield table is the most valuable page on it — it costs one weighing at harvest and replaces every published range permanently.

The loss allowance isn't pessimism

Some seeds never germinate. Some seedlings are lost. Slugs take a share. A proportion of any crop comes out unusable.

Setting Allowance for failures and losses to zero assumes every seed becomes a fully productive plant, which has never happened in any garden.

The tool shows both figures so you can see what it costs:

Loss allowance	Plants to grow
0%	8
20%	9
50%	15

At a realistic 20%, the insurance is one extra plant. That's cheap.

Weigh a serving once

It's easy to picture a portion and hard to judge one — and every figure downstream multiplies whatever you enter. A serving estimated at six ounces when it's really four inflates the whole plan by half.

A minute with a kitchen scale fixes that input permanently for that crop.

Harvest you need each week is the sanity check. If that number looks nothing like what your household actually gets through, the serving size is usually where the error is.

A long window means successions, not more plants

Weeks you want to be eating it does more work than it looks.

A plant yielding five pounds across a season doesn't give you five pounds in the week you want them. So if you want to be eating a crop for twelve weeks, the answer is normally sowing in batches rather than putting more plants in on the same day.

And if the crop all matures together, the surplus needs storing, preserving or giving away — worth planning before it arrives rather than during.

One crop at a time

Run it again for each. Yields and eating rates are nothing alike between crops — a household gets through a very different quantity of tomatoes than of parsnips, and the plants yield nothing like the same weight.

Averaging across crops produces a number that describes none of them. The per-crop figures are also more useful in practice: they tell you which crop is worth the space and which one you're growing out of habit.

If the answer won't fit

That's a real result, not a failed calculation. All the options are legitimate:

• Grow fewer crops and do them properly
• Accept eating less of that one from the garden
• Extend the window with successions, so fewer plants are in the ground at once
• Choose a higher-yielding variety

What isn't a good option is sowing the number that fits and hoping. That's how you get a glut in July and nothing in September, having done all the work anyway.

For the space side of it, the Plant Spacing Calculator on this site works out how many plants fit a bed at a given spacing — the other half of the same problem.