Development projects usually happen in this order: buildings first, parking lots second, and greenery gets squeezed in wherever there happens to be space left over. The result is often trees planted too close to façades, too small to cool anything, or in numbers that simply don’t fit the plan.
Image: The Cihelna development area. Locations where tree placement has the greatest impact on compliance with Rule 3 are highlighted in red; tree canopies (radii of 2.5, 5, and 8 meters) and their appropriate placement in terms of compliance with Rules 3 and 30 are indicated in green.
What the 3-30-300 rule is
3
30
300
Where Bosonohy stand today
Out of 1,061 buildings the analysis evaluated in Bosonohy:
- rule 3 is met by 90% of buildings: residents have little to complain about when it comes to trees in sight,
- rule 300 is met by only half of buildings,
- rule 30 by a mere 23% of buildings,
- and all three rules together by just 13% of buildings.
As almost everywhere, rule 30 is the main bottleneck: canopy coverage above 15%. A textbook picture of an outlying municipality that’s growing faster than its greenery.
The new piece of the puzzle: what happens when a developer moves in
That diagnosis alone was already useful. The new part of the analysis goes a step further and asks: what will the planned development actually do to these numbers?
We took three specific development sites in Bosonohy — Cihelna, Mlaty, and Slunečná — and calculated:
Using the same viewshed method in reverse: instead of asking what a resident can see, we ask how many windows a tree at a given spot would actually serve.
Plus a table of recommended tree counts by canopy size.
In the Cihelna site (3.7 ha, of which about 68% can be planted), for example, evenly meeting rule 30 across the whole area would mean over 500 small trees. Which is unrealistic in practice. The real, meaningful target is different: set aside 20–30% of the plantable area (roughly 0.5–0.75 ha) spread evenly across the site, which works out to about 60 medium-sized trees, and handle the rest with a smaller number of large, carefully placed trees where they’ll serve the most windows.
Why this matters more than it might seem
Image: The Slunečná development area. Locations where tree placement has the greatest impact on compliance with Rule 3 are highlighted in red; tree canopies (radii of 2.5, 5, and 8 meters) and their appropriate placement in terms of compliance with Rules 3 and 30 are indicated in green.
That’s why our planting recommendations deliberately don’t push for the maximum number of saplings, but for adequate canopy size and smart placement. Combined with blue infrastructure (retention basins, permeable surfaces, routing rainwater into green areas instead of the sewer system) that gives trees the water they need to survive drier summers.
What a developer or municipality actually gets
- A map of the best planting spots, based on real impact on rule 3: not on wherever space happened to be left over in the plan.
- Concrete tree counts and sizes needed to meet rule 30, plus a realistic compromise where the full version simply doesn’t fit spatially.
- A comparison with the surrounding area, so it’s clear whether the project is actually improving the neighborhood’s numbers or just adding another problem to the statistics.
- A decision-making basis that can be used in discussions with the building authority, the project architect, and future residents alike.
The 3-30-300 analysis with the new development module is now available for your city or project too. Whether you’re planning a new neighborhood or simply want to know where your municipality actually stands today.
