Urban Tree Wstablishment: Plant production

The Urban Tree: How Trees Are Grown, Selected, and Delivered for Our Cities

Urban trees are far more than just ornamental features lining our streets and parks. They help regulate air quality, reduce urban heat, support biodiversity, and improve the well-being of communities. But before a tree ever reaches a city street, it undergoes a long journey from nursery to planting site — and the production methods behind those trees are a crucial part of ensuring their health and longevity.

Urban area

Tree Production Systems

Urban trees are cultivated using several nursery production methods, each with its benefits and challenges:

• Bare-root trees: Grown in open ground and lifted during dormancy. Cost-effective and lightweight, but roots are exposed during planting, requiring careful handling and quick replanting.

• Rootball trees: Also grown in open ground, but when lifted, the root system is wrapped in hessian sacking and sometimes enclosed in an iron or steel cage to protect the soil mass around the roots. This allows for better root protection but makes the trees heavier and more challenging to transport.

• Container-grown trees: Grown in pots or polythene bags (usually black on the inside and white on the outside to protect from sunlight). These trees are easier to plant all year round, though they require careful irrigation to ensure the root system isn’t limited by the container size.

Uniformity and Cultivar Selection

In urban settings, consistency and uniformity are often valued for aesthetic and practical reasons. To achieve this, nurseries commonly grow clones or cultivars — genetically identical plants propagated through cuttings or grafting.A good example is Pyrus calleryana ‘Redspire’, a popular cultivar of ornamental pear known for its upright form, tolerance to urban conditions, and attractive seasonal changes.

The correct naming convention is:

Genus species ‘Cultivar’ (Common Name)

Example: Pyrus calleryana ‘Redspire’ (Callery Pear)

While cultivars offer predictability in size, shape, and performance, they do limit genetic diversity, which can increase vulnerability to pests or disease outbreaks in the long term.

Water and Irrigation Challenges

One of the greatest limiting factors for nursery trees is water availability. In container production, roots can quickly fill the space, leading to restricted growth if not carefully irrigated. Even with protective polythene bags, trees should not be left exposed to direct sunlight for extended periods, as heat can stress the roots. After planting, trees often need supplementary irrigation, especially if a significant portion of their root system was lost during lifting and transport.

Specifications and Standards

Tree production and selection follow strict industry standards to ensure quality and performance:

The National Plant Specification (NPS) outlines minimum requirements for nursery stock, covering root quality, stem form, and health.

BS 8545 provides best practice guidelines for establishing young trees in the landscape, ensuring trees have the right characteristics for survival and growth.

When specifying urban trees, details like stem girth, height, and root condition are important. The thinner the stem, the younger and typically less resilient the tree.

Transporting and Handling Trees

The journey from nursery to planting site is a critical phase. Trees are vulnerable to:

• Physical damage

• Dehydration

• Wind stress

To prevent this, trees should be transported on covered trucks and properly secured to avoid damage from wind exposure during transit. Galvanised steel cages should be avoided for long-term use after planting, as they can interfere with root growth and natural tree development. Hiller Nurseries and other major UK suppliers follow these standards, ensuring trees arrive in the best possible condition for planting.

Final Thoughts

Urban tree planting is about far more than digging a hole and adding a sapling. From nursery production methods to careful selection, transport, and planting, every stage affects the tree’s ability to thrive in challenging city environments. Understanding the behind-the-scenes process helps landscape architects, planners, and community groups make better decisions about the trees that will shape our streetscapes for generations to come.