Tree surveys in leaf and out of leaf

Tree survey timing is less restrictive than ecology timing, which is why it gets left too late. A BS 5837:2012 survey can be done in any month. What changes with the season is the confidence attached to parts of the assessment, and whether the arboriculturist has to come back.

The short version for programming a scheme. Survey between late autumn and early spring for structural detail and quick access, survey in full leaf for crown condition, and allow for a second visit if the trees are important to the layout and the first visit fell in the wrong season.

What a BS 5837 survey actually records

The standard sets out the information a survey should capture for each tree or group within influencing distance of the proposals. Reference number, species, height, stem diameter measured at 1.5 m, branch spread at four points, crown clearance, age class, physiological and structural condition, preliminary management recommendations, and an estimated remaining contribution expressed in bands of years.

From that the arboriculturist assigns a category. U for trees that should be removed regardless of development, and A, B or C in descending order of quality, each with subcategories covering arboricultural, landscape and cultural or conservation value.

The survey also produces the root protection area for each retained tree, calculated as a radius of 12 times the stem diameter and capped at 707 m2. That figure drives the layout, the foundation design and the construction exclusion zone, which is why the survey needs to exist before the site plan is fixed rather than after.

The output is a schedule, a tree constraints plan and, once a layout exists, an Arboricultural Impact Assessment with a method statement and protection plan.

Work that can be done in any month

Most of the survey is season-neutral. Measuring stem diameter, recording height and spread, identifying deciduous species from bark and bud, locating trees by survey or GNSS, assessing root protection areas and mapping constraints all happen as readily in January as in July.

Structural inspection is often better in winter. With the crown bare the arboriculturist can see included bark unions, historic failures, deadwood, cavities, bark loss and the true branch architecture. Ivy is the exception. A heavily ivy-clad stem hides defects in any season, and the honest response is a recommendation to clear the ivy and re-inspect.

Checks that need the tree in leaf

Crown condition is the one assessment that depends on foliage. Leaf density, leaf size, dieback in the outer crown, discolouration and early autumn colour are the indicators of stress and root damage, and none of them can be judged from a bare tree.

Several fungal indicators are also seasonal. Some brackets persist year-round, but many fruiting bodies appear only in late summer and autumn, so a February survey can miss decay that an October visit would find.

The practical consequence is a caveat in the report rather than a failed survey. A winter survey will say that condition has been assessed on structural grounds and that crown condition should be confirmed in leaf. An officer reading that caveat on a scheme where a category A oak sits beside the proposed dwelling will often ask for the confirmation before determination.

Bat potential noted during a tree inspection

An arboriculturist inspecting a tree records features that could support roosting bats. Woodpecker holes, frost cracks, lifted bark, rot cavities, dense ivy. That is a preliminary note, not a bat survey, and it does not satisfy the requirement for ecological assessment.

Winter is the better season for spotting those features from the ground, because the crown is visible. Assessing whether they are used is a separate exercise under the Bat Conservation Trust guidelines, carried out by a licensed ecologist, usually beginning with a Preliminary Ecological Appraisal and followed by aerial inspection or emergence surveys in the appropriate season. All bat species are protected under the Wildlife and Countryside Act 1981 and the Conservation of Habitats and Species Regulations 2017, so tree work that might affect a roost needs that separate assessment and, where a roost is confirmed, a licence.

Flag potential roost features early. Where a tree survey in November identifies three features on trees due for removal, the emergence survey window may not open until May, and the programme consequence is immediate. A Protected Species Survey has to be commissioned by a suitably licensed ecologist, and the draft documents a planning consultant prepares cannot substitute for it.

How long a survey stays current

There is no statutory validity period. Authorities commonly expect a survey carried out within the previous 12 months, and many will accept up to 24 months where the trees are stable and nothing on site has changed.

Four things shorten that. A storm between survey and submission, tree work carried out in the interim, a change to the layout that brings new trees within influencing distance, and a long gap between outline permission and reserved matters. An update visit is far quicker than a repeat survey, and a dated addendum letter usually satisfies the case officer.

Record the survey date prominently in the report and on the constraints plan. Officers check it.

Programming a spring submission

Working backwards from a target submission in April:

1. Commission the survey in September or October, while trees are still in leaf and fungal fruiting bodies are visible
2. Issue the tree constraints plan to the design team in November, before the layout is fixed
3. Resolve layout conflicts through December, adjusting building positions rather than reducing root protection areas
4. Prepare the impact assessment, method statement and tree protection plan in January and February against the settled layout
5. Commission any ecology work identified by the tree survey as soon as the features are recorded, not after the design is finished
6. Check in March whether anything on site has changed, and issue a short addendum if it has

That sequence also avoids the most expensive mistake on small sites, which is designing a layout first and then asking an arboriculturist to justify it. Root protection areas are not negotiable in the way that a parking space is.

Conditions that require checks before work starts

Permissions affecting trees routinely carry pre-commencement conditions. Tree protection fencing installed and inspected before any equipment arrives, an arboricultural method statement approved in writing, supervision by an arboriculturist at stated points, and a pre-commencement check for nesting birds where clearance falls in the breeding season between March and August.

Build those checks into the programme rather than treating them as paperwork. The fencing inspection in particular has to happen before groundworks, and a contractor who has already brought a tracked excavator onto the root protection area has created a breach that cannot be undone. Trees protected by a Tree Preservation Order or standing in a conservation area carry separate consent requirements, and works without consent can attract prosecution.

PlanScope drafts arboricultural and ecological supporting documents structured to UK planning policy, with site facts flagged rather than assumed. Survey work and the professional judgement behind it stay with your arboriculturist and ecologist. Browse all 66 report types to see what a tree-constrained site usually needs.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. For specialist technical reports, qualified professional input may be required. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.