C A S E S T U DY
2. Quality control, before lifting. Crowders Nurseries, Lincolnshire. © AECOM
Landscape Design Approach with Arup, which was highly commended at the Landscape Institute Awards in 2017. This document advocated a design response informed by character, which delivers the widest range of benefits. It includes the promotion of extensive areas of woodland to help integrate the scheme into the landscape and deliver on global challenges, including climate change.
Challenges
Over the past three seasons, over 600,000 plants have been successfully delivered to site, with no biosecurity issues identified.
As the design progressed, HS2 calculated that up to 7 million trees and shrubs would be required for Phase 1 of the project. The project is of such a large scale that multiple contractors are needed for the enabling works and main construction. This means that plant stock will be required at different times in an overall construction programme that stretches over a considerable time period (some 15 years). To achieve consistent quality across the scheme, HS2 developed a plant material specification. In 2016 they let a contract to Crowders Nurseries to grow the plants, which are then provided to contractors for planting. One of the key reasons that Crowders was selected was because they follow best practice in bio-security and plant quarantining, to minimise the risk of spreading disease.
Achievements AECOM was appointed in 2017 to independently assess and report on the quality of plants against the specification. This role includes monitoring adherence of biosecurity measures and provenance through regular nursery inspections and oversight of the detailed contract growing database. The design for Advanced Planting and Habitat Creation sites was developed in 2016 to enable a Growing Instruction for Year 1 (2017/18 season) and Year 2 (2018/19 season) stock to be placed as the Early Works Contracts were not yet in place. This was critical to delivery of the plant material as the design needs to be fixed before orders can be placed. Certainty of delivery in the planned season is also critical is it
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is often not practical to ‘hold over’ for additional seasons in large quantities. Learning from the first two planting seasons led to some standardisation of sizes for the Year 3 (2019/20 season). Cell and container grown stock for species including Oak and Blackthorn has also contributed to better establishment for these species. The establishment of plants of non-regional provenance, such as holly and oak has not been as successful and therefore it has been necessary to procure more seed to grow the same quantity as regional stock. This is being monitored but it is possible that certain species from seed from southern latitudes are not viable. All plants have been grown from seed in the UK at Crowders nurseries in Lincolnshire, reducing biosecurity risks for importing nursery stock. A method statement outlining the approach to plant health, disease and pest resistance establishes where plants will be grown in the nursery, how they will be labelled and how an outbreak of disease would be identified, contained and addressed. Over the past three seasons, over 600,000 plants have been successfully delivered to site, with no biosecurity issues identified. The plants are also inspected on arrival based on a randomly selected sample. Plants are checked for signs of pests, disease or poor health, size and root collar diameter. The results of these inspections are recorded electronically in the field, also noting the condition of packaging and adequacy of paperwork After this they are handed over to landscape contractors for planting.
Ways in which the project addressed climate emergency Climate change predictions and biosecurity risks were addressed through a detailed plant procurement strategy. This document ,drew on advice from Natural England and the Forestry Commission, who advised that seed should be collected a broader range of provenance zones to maximise resilience. These zones extend from the site, through 2° south and up to 5° south of the growing site, collecting seed from plants adapted to the warmer climate of southern England and northern France. The genetic base is increased further by collecting seed from a variety of trees of each species, including qualified and tested stands. Acquiring seed in sufficient quantities from the environment has sometimes been a challenge as tree seed production varies from season to season. The hot, dry summers of recent years, for example, have resulted in an abundance of acorns, which tend to be smaller and with reduced viability. Overall the specification has been met, but has required occasional substitutions. All woodland planting and its management will be compliant with the requirements and guidelines of the UK Forestry Standard, which sets out the UK governments approach to sustainable forest management (https://www.gov.co.uk/government/ publications/the-uk-forestry-standard).
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