24/08/2026
This Tiny Tree Could Be More Protected Than a Giant Oak
"It's only a small tree."
It's a phrase that crops up time and time again in tree disputes, planning applications, and neighbour disagreements. The assumption is usually the same: if a tree is small, surely the law is less interested in it.
Surprisingly, that's not always true. In fact, a tiny sapling could be legally protected, while a larger tree might not trigger certain legal controls at all. The key isn't necessarily the size of the tree. It's which legal regime applies.
The 75mm Rule
Let's start with conservation areas.
If a tree is located within a conservation area, you will generally need to give the local planning authority six weeks' notice before carrying out works such as felling, topping, lopping or uprooting it. However, there is an important size threshold. Conservation area controls typically only apply where the stem exceeds 75mm in diameter when measured 1.5 metres above ground level. That means a few millimetres could determine whether you need to notify the council before carrying out work. Not bad for a simple tape measure.
The Myth That TPOs Only Protect Big Trees
One of the most common misconceptions in tree law is that a tree must be large before it can be protected by a Tree Preservation Order (TPO).
It doesn't.
Government guidance makes it clear that a TPO can protect a tree of any size or species. A small sapling can be protected. A newly planted tree can be protected. Even a tree that falls below the 75mm conservation area threshold can still be protected.
Why? Because size is only one factor.
When deciding whether a TPO is justified, authorities may also consider a tree's amenity value, future potential, rarity, form, and cultural or historic significance. In other words, today's small tree could be tomorrow's landmark specimen.
The Forestry Act Uses a Different Tape Measure
Just when you think you've got the measurements figured out, forestry law introduces another set of rules.
Under the Forestry Act regime, certain small trees can generally be felled without a felling licence where they have a diameter over bark of 8cm or less when measured 1.3 metres above ground level.
Notice anything? Conservation area controls measure at 1.5 metres. Felling licence rules measure at 1.3 metres.
It's a small difference, but an important reminder that the law isn't always measuring the same thing in the same way. Forestry law also looks beyond the size of individual trees. Subject to the relevant exemptions, the key question is often the volume of timber being removed, not simply the number of trees being felled.
Bigger Doesn't Always Mean Older
Ancient and veteran trees are where size becomes particularly misleading. Many people assume that the biggest trees must be the oldest. There is no single girth or diameter that turns a tree into an "ancient" tree. Factors such as age, species, condition, biodiversity value and cultural significance all come into play. An ancient hawthorn, for example, may be far smaller than an ancient sweet chestnut. Yet both could qualify as ancient trees. When identifying veteran and ancient trees, characteristics often matter far more than measurements.
So, Does Size Matter?
Yes. And no.
Sometimes a few millimetres can determine whether conservation area controls apply. Sometimes size is largely irrelevant because a TPO can protect a tree of any size. Sometimes the law is more interested in timber volume than trunk diameter. And sometimes a relatively modest tree may be one of the oldest and most valuable around.
So before asking "How big is the tree?", ask a different question:
"Which legal rule am I measuring it against?"
In tree law, that's usually the measurement that really matters.
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