Just guessing is totally fine – it's only about a first impression.

Your plant shows a deficiency pattern.
But EC and pH are fine, and you fed to plan. What's going on?

Three rooms nobody looks into

The switch from the diagnosis course works well – because it sorts visible things. It asks about distribution and about traces, and both assume there is something to see.

But there are three places where it has nothing to sort:

Beneath the substrate. The root works in the dark, and you only see what arrives up top.

Inside the tissue. Some pathogens sit within the plant without ever reaching the surface.

After the harvest. Once the plant is dead you stop looking – and that's exactly when the third chapter begins.

Three groups deliberately do not appear in this course: bacterial diseases and plant-parasitic nematodes are described in the literature, but not documented as a relevant practical problem in cultivation. Where there is nothing, we invent nothing.

A dot runs through a track switch, finds no branch, falls through the gap into a net and is carried to three symbols: pot, leaf and storage jar.

The guiding question

The diagnosis course asks: is it crawling, or is it a coating? That's pattern diagnostics – you compare what you see against pictures you know.

With invisible causes there is no picture to compare. But there is something else, equally reliable:

Does what I see fit what I know?

That's discrepancy diagnostics. It needs no symptom picture, it needs a contradiction. And you can spot contradictions without knowing anything about the pathogen – you only need to know what you yourself did.

This question doesn't replace the switch. It hangs beneath it like a safety net: when the switch finds no track, the cause lies outside your field of view.

Four contradictions, four suspect rooms. Match where you would look:

Tap the left side first, then the matching item on the right.

The neighbouring clone is your control group

From the breeding course you know: clones are genetically identical. Two cuttings from the same mother share the same genome down to the last base pair.

Something follows from that which is worth gold in diagnosis. If two clones stand side by side, get the same water, the same feed, the same light – and one grows differently, then the difference cannot be genetic. It has to be environment or disease.

That's an experiment with a control group, and you set it up without noticing.

So a single outlier among clones is always a signal. If the whole room grows badly, you think of climate or water. If one grows badly and the rest are fine, the suspicion of something invisible becomes concrete.

Three routes to proof when the eye fails

The diagnosis course gives you three tools that cost nothing: a loupe, white paper, the underside of a leaf. All three assume there is something to see.

Here you get the sequel – three routes to proof for causes without a picture:

Expose. What you can't see, you can often make visible. Looking at a root at the edge of the pot and smelling it costs nothing and answers more than any remote diagnosis.

Compare. The neighbouring clone from the last card. Same genetics, same treatment – an outlier is a finding.

Test. Some things simply cannot be recognised by looking, only in a lab. That's not a defeat, it's the right answer to the right question.

Each of the next three lessons belongs to one of these routes.

One of twelve clones is stunted.
Climate, light and feed are fine, the other eleven grow normally.
What have you already ruled out?

The key takeaways

  • The guiding question is: does what I see fit what I know?
  • Three rooms stay hidden from the switch: beneath the substrate, inside the tissue, after the harvest
  • Three routes to proof replace the look: expose, compare, test
  • Clones are a control group you already have – an outlier is a finding

🎯 Hands-on mission

Run the four contradictions past your grow diary and ask yourself for each: would I even have records to notice it? The guiding question is "does it fit what I know" – and what you know is in your notes or nowhere.

To the grow diary →

Lesson complete!

The first room lies directly beneath your feet – and what happens there shows up above as something else entirely.

  • I know the guiding question: does what I see fit what I know?
  • I know the three rooms nobody looks into
  • I know the three routes to proof when the eye fails
  • I know the neighbouring clone is my control group
To the grow diary → Continue to the next lesson →

Something still unclear?