The square foot gardening app that draws the grid for you

What square foot gardening actually demands of a planner

The method, developed by Mel Bartholomew in 1981, replaces long rows with a grid of 1-foot squares. Each square holds a different crop, and the number of plants in that square depends on how much room the crop needs. It is a brilliant system for small beds — and a fiddly one to plan by hand, because every square is a separate small decision.

Four decisions have to happen for every square you fill:

• How many fit? Spacing in inches converts to a count per square.
• Will it shade its neighbours? Tall crops belong on the north side.
• Does it get on with what's next to it? Some pairings help, some don't.
• When does it go in? Which depends on frost, not on the calendar month.

Do that sixteen times for a 4×4 bed and you understand why most people give up and plant whatever the garden centre had in stock. An app earns its place by answering all four as you tap, not by making you look them up.

How Niwa handles each square

1. The grid matches your actual bed

Enter the bed dimensions — 4×4, 4×8, 2×8, a 3×12 border, whatever you built — and Niwa lays a one-foot grid over it. The header shows the size and how full it is, so a 4×8 bed reads 4' × 8' · 24/32 planted. You can build several beds and keep them in separate gardens.

2. Plants-per-square is calculated, not remembered

Tap a square, pick a crop, and Niwa fills it at the correct density and prints the count on the cell — ×16 for carrots, ×4 for leaf lettuce, a single icon for broccoli. The rule underneath is simply 12 inches divided by the crop's spacing, squared:

You can run the same maths yourself in the browser with the plants per square foot calculator — it is the identical formula the app uses.

3. Companion conflicts show up on the grid

This is the part a paper grid cannot do. When two crops sit in neighbouring squares, Niwa puts a small dot on the border between them: green where the pairing is beneficial, red where the two are better separated. Basil beside tomatoes goes green. Onions beside beans goes red. You see it at the moment you place the plant, which is the only moment the information is useful.

4. Every crop gets a date, not a season

Niwa reads your location once, finds your average last spring frost and first autumn frost, and works backwards per crop. Tomatoes get “start indoors 6–8 weeks before last frost”; peas get a direct-sow window that opens weeks earlier. Each plant in the bed appears on a month-by-month timeline with its sowing, transplant and harvest bands, so you can see at a glance which squares are busy in March and which are still empty.

Planning your first bed, step by step

1. Measure the inside of the bed

   Inside dimensions, not outside — the timber does not grow anything. Never build wider than 4 feet if you can only reach it from both sides, or 2 feet if it is against a wall.

2. Place the tall crops first, on the north edge

   Tomatoes, trellised cucumbers, corn and pole beans cast shade. Put them in before anything else so the shading decision is already made. In the southern hemisphere, reverse it.

3. Fill the big single-square crops next

   Broccoli, cabbage, peppers, eggplant. These are 1-per-square or larger and they dictate how much room is left. Watch for red dots as you go — brassicas next to nightshades is a common accidental clash.

4. Backfill with the dense fast crops

   Radishes, carrots, lettuce, spinach. These are your 9s and 16s, and they are also your succession crops: whatever empties first gets replanted mid-season.

5. Check the calendar tab before you buy seed

   Now the bed is full, the calendar shows what needs starting indoors and when. Buy from that list rather than from the seed rack — it is the step that stops you owning nine packets of courgette.

A worked 4×4 layout

Sixteen squares, planned north-to-south, no red dots:

That is 106 plants in sixteen square feet. Basil sits with the tomatoes deliberately; marigold goes in the corner as a pest deterrent; the onion family is left out entirely because beans and alliums antagonise each other and beans occupy two squares here.

What Niwa does not do

Worth saying plainly, because it may rule the app out for you:

• iPhone only. iOS 18 or later. No Android, no iPad-optimised layout, no web version.
• No cloud sync. Plans live on the device. That is deliberate — no account, no server — but it means no sharing a plan across two phones.
• Not a plant identifier. It plans and schedules; it does not diagnose photos of sick leaves.

New to the method?

If you have not built the bed yet, start with the method rather than the app. Our complete square foot gardening guide covers Mel's Mix soil recipe, grid construction, succession planting and crop rotation, with a spacing chart for 30+ crops. Then come back and lay it out in twenty minutes.