The map is describing the air, not the ground

A plot, drawn in plan. A boundary line, a hedge running along one side, four contour lines marking a gentle slope. In the lowest corner, one area is shaded darker than the rest of the plan, labelled in two words: frost pocket.

Every other line on this map is describing the ground. That one is describing the air above it.

What is this map actually showing?

Where cold air collects on a clear night, which is not the same question as where the ground is lowest, even though the two are related.

The contour lines record the shape of the land — a fact that doesn't change from one night to the next, and a different question from what a spade cut into the same ground would reveal about the soil beneath it. The shaded corner records something that moves: air, cooling and sinking after dark, arriving in that corner because the slope carries it there. One layer of the drawing is permanent. The other is a nightly event that happens to land in the same place every time.

Why does cold air collect in one corner instead of spreading evenly across the plot?

Because cold air is denser than warm air, and denser things run downhill and pool exactly the way water does.

After sunset the ground loses heat fastest and the air right above it cools with it. That cooled air is heavier than the air around it, so it slides down the slope and settles in the lowest part of the plot it can reach — the corner in the drawing. A hedge along the low side makes it worse rather than better: solid enough to stop the cold air draining any further, it acts as a dam, in the same way a water butt's overflow sits at exactly the level past which the water inside it does not rise — one holds a level of air behind a barrier, the other holds a level of water at an outlet.

What makes a good print of a map like this?

Keeping the shading small and specific to the actual pocket, not spread across the whole low half of the plot for visual weight.

A frost pocket is usually a modest area — one corner, one dip, the ground behind one obstruction — and shading more than that turns an accurate observation into a vague warning about "the low end," which isn't what the map is for. The contour lines earn the shading's precision; without them the shaded patch is just a dark shape with no argument behind it.

Who owns the shape of a plot, or the words frost pocket?

Nobody. A plot's boundary, its slope and a hedge line are facts about one piece of ground, and the term frost pocket is ordinary language used by anyone who gardens on a slope.

What is owned, and worth knowing before it comes up, is a named plant variety: a new variety's name carries its own protection, in the same way a brand name does, under plant breeders' rights — a real one would need the ordinary permission before going on a shirt. Nothing on this particular map names a crop yet, but the moment one does, that's the question to ask first.

Does a frost pocket need a hillside to form?

No — any dip that stops cold air draining further will do it, hillside or not. A single low bed with a solid fence on its downhill side can behave exactly like a frost pocket on a whole hillside plot, just at a smaller scale.

It's the same physical logic working at the size of one bed rather than one field — the opposite of what happens in a bell cloche, which traps warm air instead of letting cold air escape: one pocket holds heat in on purpose, the other loses it and has nowhere else to go.

How would anyone even find their frost pocket without surveying gear?

Most people find it the way this map implies — after the fact, by losing something to it.

A row that comes up everywhere except one corner, or a plant that survives an ordinary winter but dies in that one spot two years running, is usually the first evidence anyone gets. A map like this tends to get drawn after that loss has already happened once — contour lines and a shaded corner are what a gardener draws having worked out, the hard way, where the cold actually goes.

Does it print well?

Yes — flat contour lines and one block of shading are simple, hard-edged shapes that hold up well at any size.

Navy for the boundary, the hedge and the contour lines keeps the map reading as a plan rather than a picture; white or a very pale tint for the shaded corner is enough to mark it out without needing a second colour. Pale grey as the garment keeps the whole thing close to the tone of a real survey sheet.

How do I get one made?

Describe your plot at JustOG — the slope, where the hedge or fence runs, and where the cold actually settles. Pick a direction, drag the crop frame, see it composited on the real garment, and it's made to order and shipped.

Designs other people have published are in the shop.

Four contour lines describing the ground, and one shaded corner describing what happens above it.