Ensuring Safety and Health
The Garden prioritises both visitor safety and tree health. We manage our trees carefully to also protect surrounding roads, neighbouring properties and other Garden collections, especially as our trees age and grow in size.
How We Manage Our Trees
Our dedicated Trees and Shrubs Team leads our arboricultural operations, and is responsible for the care and maintenance of the collection. For some tasks e.g. felling of large trees and terraventing (the creation of channels in soil for better root oxygen and nutrient access to improve tree health), they may also appoint specialist arboricultural contractors to assist them in this work. Tree safety is assessed through two main inspection systems:
- Full Collection Survey – conducted by an arboricultural consultancy every three years, this survey records each tree’s details and hazards using specialized software. This generates an action list with timelines for any necessary work.
- Continual in-House Inspections – our team also performs ongoing reviews, addressing any new hazards and updating maintenance plans as needed.
Lists of work are produced from the surveys. This can range from moving benches and removing ivy to more significant efforts like dead wooding, branch reductions, or, in some cases, tree removal. To guide our decisions, we sometimes use specialist tools, such as a resistograph drill to assess wood resistance or a PiCUS tomograph that uses sound waves to detect for any internal decay. This extra information is then used to inform the plan for the tree being examined.
Balancing Safety with Tree Conservation
In managing our trees, we often balance safety requirements with a commitment to conservation. In some cases, such as with our historic Quercus x warburgii (Cambridge Oak), we prioritize the tree by installing barriers rather than performing extensive reductions, allowing it to be enjoyed from a safe distance while preserving local biodiversity. We have also terravented and mulched beneath the tree, which involved injecting the soil with air to improve the soil, which will also improve the tree’s health.
Responding to Challenges
Drought has posed significant challenges in recent years. We support growth of young and newly planted trees by watering through treegators and bowsers but mature trees, grown here in relatively dry conditions, have adapted to be resilient. However, dry conditions can increase the risk of “summer branch drop” (SBD), where mature trees can shed limbs unexpectedly. Over the summer season it may be necessary for us to take preventive steps, roping off certain areas and monitoring susceptible species closely.
Additionally, our team has made significant decisions regarding declining trees, such as the 2020 work on our Caucasian wingnut (Pterocarya) stand near Brookside Lawn. Following a detailed inspection, we reduced these trees to encourage a new generation, which is now showing promising growth.
A Sustainable Future
As we look forward, we are continuously planning for the next generation of trees in the Garden. Some younger trees are selected to grow and replace older ones as needed, ensuring the Garden’s legacy endures.
Sadly, with a tree collection dating back to 1846, it will mean some trees are coming to the end of their natural life. In 2022 we lost Newton’s Apple tree Malus pumila Rosaceae ‘Flower of Kent’ during Storm Eunice. Tilia tomentosa (silver-leaved lime) near our Old Main Gate had to be removed in 2022. This majestic tree, over 150 years old, had weakened and posed a safety risk, prompting an emergency tree works application to the City Council for removal. Most recently in 2024, severe damage to Pinus pinea (stone pine) a champion tree located behind the Glasshouse Range, meant the tree failed and had to be removed for safety of our staff and visitors.
Each year we plant new trees in the Garden, sourcing seed from our own collecting trips, other collections and suppliers. Rather than replacing like-for-like, we focus on adding trees which add value to our collection, and which are suitable for long-term cultivation in a changing climate – though it can take several years to propagate and grow trees from seed for planting.
Every tree management decision considers both public safety and the health of the tree. All work is carefully thought through and involves many lines of decision making in order to consider the different factors associated with managing an aging tree population in a busy visitor attraction.