§ Grants & compliance

Measuring hedgerow density for SFI HRW1/HRW2 compliance

Q: What does SFI HRW1 actually require?

HRW1 (assess and record hedgerow condition) requires a record of the structural condition of every hedgerow on the parcel, including gappiness, height, base width, and signs of management. SFI guidance uses qualitative bands like 'gappy' or 'good' but doesn't define the threshold quantitatively. A measured porosity figure substitutes a number that any auditor can replicate from the photograph.

Q: What is HRW2 and how is it different?

HRW2 (manage hedgerows for the benefit of pollinators and farmland birds) pays per metre of hedgerow managed under specific protocols, including no annual cutting on at least half the hedge length and rotational cutting elsewhere. The condition assessment from HRW1 informs which hedges qualify for HRW2 and at what rate. Linked, but separate.

Q: Will Defra accept an optical porosity figure as evidence?

SFI evidence requirements ask for photographs and a written description of condition. A measured porosity figure with the photograph it was derived from is stronger than a written description alone, because it's reproducible. The figure pairs with the photograph in the audit pack and replaces the subjective bit of the written description with a number.

Q: How many photos do I need per hedge?

One frame every 5-10 metres of hedge length, walked along the full length. A 200-metre hedge produces 20-40 frames. The batch average is the figure that goes on the report; the per-frame figures show the variability and weak-spot locations.

Q: Does it work for laid hedges?

Yes. A newly-laid hedge measures very low porosity (the laid stems block most of the gaps), which is the correct figure for an early Building-stage hedge. Note the management date in the report and the low figure becomes evidence of recent successful laying rather than a problem.

Q: What if I don't know the optimal range?

For SFI evidence, the optimal range matters less than the documented number. The 20-50% band is a common biology-led benchmark for healthy hedges, but audit reports work fine simply showing the measured figure paired with the photograph. The auditor doesn't need to know what 'good' is; they need to see what you measured.

Published 6 May 2026· 8 min read· Hedgerow · SFI compliance

SFI HRW1 (assess and record hedgerow condition) and HRW2 (manage hedgerows for pollinators and farmland birds) both rely on a judgement most farmers and even most agronomists make in 30 seconds: is this hedge gappy or not? The Defra guidance describes the categories qualitatively. The audit pack expects photographs. What it doesn’t expect, but increasingly accepts, is a measured porosity figure pinned to each photograph - a number any auditor can verify by re-running the same analysis.

This guide covers the workflow: how to capture the photographs HRW1 asks for, how to add the porosity figure that turns “a bit gappy in places” into a number, and how to assemble the evidence pack for the next inspection.

What you will learn

What HRW1 and HRW2 actually require, in plain terms
How to capture compliant photographs of every hedge on a parcel
How to attach a porosity figure to each photograph
How to assemble the audit pack so you can re-do it next year
What the typical figure ranges look like, and where the lines sit

HRW1 in plain terms

HRW1 pays for the act of assessing your hedgerows and keeping a record. The record is a list of hedges with: rough length, structural condition, height, base width, signs of recent management, and any gaps that need attention. Defra’s guidance gives you four condition categories - favourable, moderate, declining, and broken - mapped roughly to the Adams hedgerow lifecycle.

The slipperiness is in the categories themselves. “Moderate condition” is defined narratively. Two assessors looking at the same hedge can disagree, and the auditor reviewing the report a year later has no way to verify which one was right unless the photograph clearly settles the question. This is where a measured porosity figure helps.

HRW2 in plain terms

HRW2 is the management payment, per metre of hedge length under specified protocols. The qualifying conditions include: no annual cutting on at least 50% of the hedge length, rotational cutting on the rest at intervals of three years or longer, and protection of fruiting and flowering structures during pollinator-relevant seasons. HRW2 doesn’t require a porosity figure directly, but the condition assessment from HRW1 is what tells you which hedges qualify and at what rate. So the HRW1 evidence indirectly drives the HRW2 payment.

Capturing compliant photographs

The photograph rules are the same as any porosity capture. Side-on, perpendicular, sky behind the hedge, camera level. See the hedgerow capture guide for the full protocol. The HRW1-specific additions are about coverage rather than technique:

Every hedge on the agreement parcel needs at least one frame. Hedges over 50 metres need a frame every 10 metres or so.
Tag each frame with GPS (most phones do this automatically). The audit pack expects to know which photograph is which hedge.
Photograph in the same season each year. In-leaf summer captures are the normal SFI standard; bare-branch winter captures are usable but harder to compare year-on-year if you mix seasons.
Note the management date on each hedge somewhere. A hedge cut in March looks different in June than the same hedge uncut for five years.

Adding the porosity figure

Upload the batch to the analyser in hedgerow mode. Each photograph gets a per-photo porosity percentage, a confidence label, and a spatial heatmap showing where the dense and open zones sit. The batch average is the figure that goes on the per-hedge report line.

Typical ranges in the field, broadly:

0–20% porosity: very dense. Newly laid, recently coppiced into vigorous regrowth, or a stockproof hawthorn that has been managed annually for decades.
20–50% porosity: the agronomically healthy band. Wind sifts through, biodiversity thrives, the hedge is doing the jobs SFI wants it to do.
50–75% porosity: declining. Structural gaps starting to appear. Candidate for HRW2-funded gap-up planting or rotational laying.
Over 75% porosity: broken. The hedge is mostly gaps. Replanting or substantial restoration needed.

These bands are working benchmarks, not Defra-approved thresholds. The figure itself is what goes in the report; the bands are interpretation guidance for your own management decisions.

Assembling the audit pack

The PDF the analyser produces in Pro mode is the right format for inclusion in the SFI evidence folder. It has the per-photo porosity readings, the batch average, the confidence label, and the spatial heatmaps that show where the gaps are. Add a line on each per-hedge report noting: hedge ID, length in metres, measured porosity, season of capture, management dates, recommended action.

Repeat the process every year on the same hedges, in the same season. After three or four years you have a time series that is audit-defensible, year-over-year comparable, and useful as input to HRW2 payment claims and management decisions.

Run your hedge survey through the analyzer

Drop a folder of hedgerow photographs into hedgerow mode and get a per-hedge porosity figure with audit-ready PDF in under a minute.

Try the hedgerow analyzer →

Frequently asked questions

What does SFI HRW1 actually require?

HRW1 requires a record of the structural condition of every hedgerow on the parcel: gappiness, height, base width, signs of management. SFI uses qualitative bands like ‘gappy’ or ‘good’ but doesn’t define them quantitatively. A measured porosity figure substitutes a number any auditor can replicate from the photograph.

What is HRW2 and how is it different?

HRW2 pays per metre of hedgerow managed under specific protocols (no annual cutting on at least half the length, rotational cutting elsewhere). The HRW1 condition assessment informs which hedges qualify for HRW2 and at what rate.

Will Defra accept an optical porosity figure as evidence?

SFI evidence asks for photographs and a written description. A porosity figure with the photograph it was derived from strengthens the description because it’s reproducible.

How many photos do I need per hedge?

One frame every 5–10 metres along the full length. A 200-metre hedge produces 20–40 frames. The batch average is the figure on the report.

Does it work for laid hedges?

Yes. A newly-laid hedge measures very low porosity, which is the correct figure for an early Building-stage hedge. Note the management date in the report.

What if I don’t know the optimal range?

For SFI evidence, the documented number matters more than the optimal range. The 20–50% band is a useful benchmark; reports work fine showing the measured figure paired with the photograph.