Most garden apps pin crop history to a bed, so when you move the beds it's gone. Here's why this one attaches history to the soil, and what that gets you.
Photo: George Chernilevsky · Public domain, via Wikimedia Commons.
The bug you only meet in year three
Draw your garden in almost any planner. Four raised beds, tidy rectangles, each one a little record with a name. Plant tomatoes in Bed 2. Next winter you decide the layout was wrong, pull Bed 2 out, widen the path, and put two smaller beds where it used to be.
Where did the tomatoes go?
In a tool that hangs history on the bed, they’re gone. Bed 2 doesn’t exist anymore, and the fact that a particular patch of soil grew nightshades last year got deleted along with the rectangle you drew. The new beds start clean, the rotation warning never fires, and you plant tomatoes back into the same ground and find out the hard way.
This is why so many garden planners are really single-season toys. They’re perfectly good until your first redesign, and rotation is the one feature that only matters across redesigns.
Three separate things
This planner keeps apart what most tools mash into a single object:
A plot is a permanent patch of coordinates. It’s the yard. It doesn’t change when you change your mind.
A bed is a shape laid over the plot for a while. It has a size, a structure, and a lifespan. You can move it, resize it, or delete it.
Occupancy is the record of what grew in which spot in which season.
Occupancy sticks to the plot’s coordinates. When you delete a bed, you delete a rectangle, and what grew there stays on record. When you ask “can I plant tomatoes here?”, the planner takes the patch you’re pointing at, checks it against everything that has ever grown on that ground, and answers from the soil’s own history.
Rearrange the yard as often as you like. The history is in the dirt, which is also where the actual problem is.
What the history is for
Rotation intervals exist because pests and diseases hang around in the soil. The interval is set by plant family, because that’s the level the problem works at, and the corpus keeps one rule per family with the interval its sources support:
Don't plant nightshades where nightshades grew in the last 3 years
If you skip this, you lose real yield. The planner warns you.
How it works: Alternaria solani (early blight) and Septoria lycopersici overwinter on tomato debris and solanaceous weeds; a 2-3 year break plus debris removal starves this inoculum. Fusarium has a very narrow host range, so rotating away from the host is effective. Verticillium is the exception. Its microsclerotia persist ~10 years and it infects 300+ host families, so a garden-scale rotation does not control it.
Evidence: checked against 5 sources in the research-based literature.
Verticillium wilt tends to affect a wide range of hosts and can infect many unrelated plants. Fusarium spp., on the other hand, have very narrow host ranges.
Remedy
Plant nightshades in different ground, or wait until 3 years have passed since this ground last held them. Clear and remove the old debris either way, because the inoculum overwinters on it.
If you skip this, you lose real yield. The planner warns you.
How it works: Melittia cucurbitae overwinters as a pupa in the soil where its host grew and emerges the next summer; Anasa tristis overwinters as an adult in sheltered sites (plant debris, under boards or rocks) and flies to cucurbits in spring. A host-free break cuts local carryover, but both are strong fliers that re-invade from a distance, so rotation is only partial and works best paired with fall sanitation (destroy spent vines).
Evidence: checked against 4 sources in the research-based literature.
… squash vine borers spend the winter in the soil near their host plants ... Practice rotation ... planting cucurbits in different areas of your garden if possible, or alternate seasons
Crop rotation away from previously infested fields helps reduce local populations, as overwintering pupae remain in the soil. However ... fields often need to be rotated more than 5 miles away as SVB can fly into fields from long distances.
Squash bugs can live through the winter as adults in sheltered places, such as under plant debris, around buildings, or under rocks. When adults come out in the spring, they fly to growing cucurbit plants.
Plant cucurbits in different ground, or wait 3 years. Destroy the spent vines in autumn and clear debris and boards nearby. The pupae overwinter in the soil where the crop grew, the adults in the shelter around it. Rotation is only partial; both pests fly in from a distance.
If you skip this, you lose real yield. The planner warns you.
How it works: Plasmodiophora brassicae forms thick-walled resting spores that survive in soil more than 10 years. They germinate in wet, acidic soil (pH < 7); liming above ~7.2 suppresses infection. Spores outlast any garden rotation, so a host-free break reduces but does not clear inoculum.
Evidence: checked against 3 sources in the research-based literature.
Plant brassicas in different ground, or wait at least 4 years (extension recommends 4 to 7). Rotation alone is not a cure, because the resting spores outlast it. Raising soil pH above ~7.2 suppresses infection.
Look at the grades on these. None of them is a rock-solid claim with one crisp number behind it. The sources give ranges, and the brassica interval especially comes with an extension recommendation the rule quotes, plus an admission that even the long interval isn’t a cure. The rule says so and keeps the range, where a single number would only sound more authoritative.
The rotation advice you were given is probably too strong
The strict version of rotation folklore says everything has to move every single year. The research doesn’t support that, and following it to the letter in a small garden gives you worse plans.
You must rotate every crop to new ground every single year.
You don't have to move every crop every single year by rule. What matters is keeping each crop family out of the same soil long enough to starve its diseases, commonly three to five years. Rotating yearly is a good habit. It isn't a law, and perennials like asparagus and rhubarb stay put for years.
What is known
Rotation works by starving a pathogen out of the soil, so the right interval depends on how long that pathogen survives, and for many diseases that cannot be stated precisely. Extension advice is to keep a crop family out of the same soil for three to five years; clubroot of the mustard family can survive seven years, bacterial spot needs at least two years without a host, and soil-dwelling soft-rot bacteria are not managed by rotation at all. Moving families every year is a sensible habit. It isn't a law, and Milpa's rules carry the intervals that have named mechanisms. Perennials are the exception. Asparagus and rhubarb stay in one spot for years, and cultivating too deep damages asparagus crowns.
Rotating crops each year and only growing vegetables in the same family in the same area every 3 to 5 years starves out most pathogens that cause stem and leaf diseases.
Cultivating too deep, or at the wrong time in the season, can damage the crowns and emerging spears.
A four-bed garden can’t give brassicas a four-year gap by rotating in a neat cycle. Something has to give, and knowing which rules carry the load lets you give in the right place.
The break year, as a real option
When a patch of ground has taken on too much rotation load, the planner offers more than a warning. It suggests a restorative break: a rest year that puts a nitrogen fixer (a plant that feeds the soil) on the ground, with the option of a hardy overwintering crop, so the season isn’t wasted while the clock runs down.
That’s what separates a planner from a validator. Saying “no” is easy. Saying what this ground wants instead is the part that took the whole data model.
The trade
Attaching history to the ground costs more than attaching it to beds. Every occupancy record carries its own geometry, every rotation check is a bit of spatial math where a bed tool does a simple lookup, and the model is harder to explain in one sentence. In exchange, the app is still right in year five, after you’ve moved everything twice.
