Farkesht technical dossier
Designing and maintaining urban trees
A street tree lives in one square metre of open ground, between compacted sub-base, buried services and a clearance envelope that will not let it grow. This dossier sets out what kills it and what keeps it.
- Soil per m² of canopy
- 0.6m³/m²
- Headroom over the carriageway
- 4.5m
- Reachable age with a proper pit
- 50years
Updated August 20, 2026Farin Kesht Taban Co.
The problem
A street tree is not an orchard tree
Same species, same climate — and six pressures that do not exist in an orchard and never go away on a street.
Compacted, undersized soil
A road sub-base has to be compacted so it does not settle; that same compaction denies the roots penetration and air.
Shallow, unreliable water
Runoff crosses the asphalt and never reaches the pit, and hand watering tends to be shallow and irregular.
Salinity and de-icing salt
Road salt and saline irrigation accumulate in the sealed soil of a pit, with nowhere to leach away to.
Pruning wounds and impacts
Heavy topping to clear the carriageway, and vehicle strikes, are the way decay gets into a trunk.
Buried services
Cables, pipes and ducts take away usable root volume, and every excavation severs part of what is left.
Heat island
Higher surface temperatures and reflected heat from façades raise transpiration and sharpen water stress.
The key figure
Canopy size is set by soil volume, not by species
The rule is simple: roughly 0.6 m³ of rootable soil for every square metre the mature canopy will project. Every other argument comes after that number.
- 4 m8 m³
- 6 m17 m³
- 9 m38 m³
- 12 m68 m³
A plain pit: about 4 m³
This is why two trees of the same species and age on one street end up different sizes. The difference is usually under the paving, not in the sapling.
Species
A species that can live with a street
Three pressures decide it: drought, salinity and pollution. The table below is a general guide, not a prescription for a particular street.
| Species | Drought | Salinity | Pollution | Mature height |
|---|---|---|---|---|
| Oriental planePlatanus orientalisExcellent shade and very tolerant of pollution, but thirsty, and it will not last in a small pit. | Low | Low | High | 25 m |
| AshFraxinus rotundifoliaA balanced choice for streets: reasonably quick and a canopy that stays manageable. | Moderate | Moderate | High | 18 m |
| ElmUlmus minorCopes with heavy soils, but is susceptible to Dutch elm disease and needs monitoring. | Moderate | Moderate | Moderate | 20 m |
| White mulberryMorus albaTough and undemanding; fruitless cultivars are preferred along footways. | Moderate | Moderate | High | 12 m |
| Eldar pinePinus eldaricaSuits dry regions, but gives little shade and dislikes compacted soil. | High | Moderate | Moderate | 20 m |
| Japanese pagoda treeStyphnolobium japonicumOne of the toughest options for urban conditions, with high drought and salt tolerance. | High | High | High | 15 m |
No species is finally chosen without a soil and water analysis of that street. This table is where the conversation starts.
Care programme
Four stages, four different jobs
What is needed in year two is wrong in year fifteen. The care programme changes with the age of the tree.
Establishment
Years 1–3
- Deep, regular watering until the roots are established
- Temporary staking — and removing it on time
- Weed control and mulching over the root zone
Formative pruning
Years 3–10
- Formative pruning to build a central leader and clear stem
- Removing competing leaders and narrow-angled unions
- Raising the crown gradually to the clearance envelope
Mature maintenance
Year 10 onward
- Light periodic pruning instead of heavy topping
- Safety inspection and recording it against the tree record
- Feeding based on soil and leaf analysis
Treatment and recovery
As required
- Trunk injection for pests and deficiencies that spraying will not reach
- Soil remediation and decompaction of the root zone
- Wound management and monitoring of trunk decay
Safety
Tree risk assessment, by a method someone can check
Risk is two things together: how likely the part is to fail and strike, and how bad it is if it does. The matrix below is the standard arrangement.
| Rows: likelihood of failure and impactColumns: severity of consequence | Negligible | Minor | Significant | Severe |
|---|---|---|---|---|
| Improbable | Low | Low | Low | Low |
| Possible | Low | Low | Moderate | Moderate |
| Probable | Low | Moderate | High | High |
| Imminent | Low | Moderate | High | Extreme |
Low
Record it and look again at the next inspection.
Moderate
Scheduled work within the same working season.
High
Prioritised work — usually remedial pruning or restricting access.
Extreme
Immediate action and cordoning until the risk is gone.
The outcome of an assessment is rarely felling. In most cases remedial pruning, reducing end weight, or moving what sits under the tree brings the risk back to an acceptable level.
Working with municipalities
From tree inventory to annual report
A municipal programme is not an orchard: the scope is large, public safety is involved, and everything has to be documented and auditable.
01
Inventory and tree records
Position, species, stem diameter and condition captured per tree, into one dataset.
02
Survey and risk assessment
Safety assessment of higher-risk trees against the standard matrix, documented as it goes.
03
Prioritised programme
Turning the findings into a ranked action list with time and resource estimates.
04
Execution and supervision
Pruning, trunk injection, soil remediation and replacement planting, under technical supervision.
05
Reporting and handover
Periodic reports, updated tree records, and training for the client’s own maintenance crew.
Some of the urban work
Projects recorded under urban landscape and trunk injection.
For tenders and public calls, the qualification documents, the project record and a sample technical report are supplied as one submission. Contact the office to request it.
Questions
What parks managers ask
The six that come up most.
Why have the trees along one street declined together?
When decline happens simultaneously along one axis, the cause is usually shared: a change in watering, a services excavation, saline water, or soil compaction after construction. Diagnosis starts with soil sampling and root inspection, not with spraying.
What is the minimum tree pit size?
It depends on the mature canopy, not the sapling. A tree with a six-metre canopy needs roughly 17 m³ of rootable soil; that volume can be provided under the footway using structural soil or a suspended pavement system.
When is the best time to prune street trees?
Structural pruning in winter dormancy, and safety pruning whenever a risk is identified. Heavy topping in late spring and summer does the most damage.
Is trunk injection suitable for street trees?
Yes, and on busy streets it is often the only practical method: no spray drift, no road closure, and a measured dose per tree. It is used for nutrient deficiencies and some sap-feeding pests.
Can we change the dominant species along a street?
Gradually, yes. Replacing everything at once removes the shade and concentrates the risk; the usual approach is phased replacement with a mix of species, so no single pest can take out the whole avenue.
What is supplied for a tender?
A project record with comparable work, licences and memberships, a technical scope of services, and a sample report. The exact list follows the tender documents.
An avenue or a park where the trees are giving cause for concern?
One visit and an initial assessment settle whether it is roots, water or safety.