How to Survive on the Street (Street Trees Part II)

In my last blog post I championed a special type of tree: The Street Tree. A couple of people pointed out that if we planted trees in our streets, they are likely to get too big and cause nuisance issues and damage our infrastructure. The planting of any street tree which caused such issues could not be deemed a success. Street trees need to thrive in the urban environment without causing damage to surrounding infrastructure, and without causing conflict with neighbours or users of the highway. How can this be achieved?

To answer this question it is helpful to think about what a tree needs to thrive in the urban environment.

Firstly, all temperate trees need soil. They need sufficient soil volume relative to their size and leaf area. The soil needs to be well structured, to allow water and air to flow through it. Most roots need air to survive. The soil should be able to supply all the nutrients that the tree needs.

Most people have never thought about soil in the urban environment. Why would you?! There is soil underneath our roads and pavements isn’t there? Isn’t there?? Well….yes (perhaps), but the structure of the road (the wearing course, base course and subbase) occupies the space where the biologically active soil should be. If there is soil (‘subgrade’) beneath a road, it is likely to be compacted (lacking air) and poor quality.

Trees also need access to water. Water is essential for photosynthesis and nutrient transport. Fortunately groundwater is not often in short supply on our island, but extreme weather events are predicted to increase, so drought is something we need to think about. However, too much water is also bad because waterlogged soils are devoid of air.

When transplanting nursery trees to any location, it is important to provide the young tree with support until the roots get a chance to grow into the surrounding soil and provide sufficient anchorage. In an urban environment this can be challenging as tree stakes don’t look great, they create trip hazards and need to be maintained/removed at the appropriate time to avoid damaging the tree. Fortunately underground guying systems have been developed to provide ‘invisible’ support to newly planted trees.

It is a common misconception that tree roots grow deep into the ground. Due to the requirement for air (and gas exchange) most trees grow in the top 60cm of soil. For this reason trees naturally send their roots out close to the surface. If soil is available below a hard surface, trees often need a bit of encouragement to send their roots downwards but the roots will be quite happy there once they find it, as long as the soil remains aerated. ‘Root deflectors’ and ventilation pipes can be used for this purpose.

Here is an example of a modern ‘tree pit’, courtesy of GreenBlue Urban.

So far, we have thought about how a tree may be nurtured to prevent it becoming a troublemaker, but there is nature as well nature to consider in this noble endeavour. As well as providing a tree with a suitable rooting environment, we also need to think about the species of tree we plant. Every planting opportunity presents a different set of constraints, and every species available at the tree nursery has different characteristics. We must ensure that the right tree is planted in the right place for the right reasons.

We should think about a tree’s mature height and canopy spread, for example. Reflected heat from hard surfaces, reduced water availability due to run-off from impermeable surfaces, and contamination from de-icing salts are just some of the physiological challenges that street trees may have to deal with, and some species cope better with these challenges. Trees with prominent surface roots (e.g. Cherry) can cause problems. Nuisance issues related to honeydew or rotting fruit are an important consideration. Shade can be beneficial but can also be viewed as a nuisance, so it’s important to think about the type and extent of shade the canopy will produce when in leaf. Getting all these factors right will reduce the likelihood of conflict occurring and reduce future pressure to remove trees.

If we can nail the nature and nurture factors, a street tree should be able to thrive in the urban environment without causing conflict, but we don’t live in a perfect world. There are many existing street trees that were planted without due consideration for the factors described above. This is where management becomes essential. For example, we can prune trees regularly to maintain their height or canopy spread. Where roots begin to disturb hard surfaces, we can repair and adapt the surfaces in a sensitive way. If seasonal fruit drop is causing a nuisance issue, then we can increase the street cleaning regime during that part of the year. There are many other innovative ways that these issues can be managed, if there is a desire to do so.

By thinking about the nature and nurture issues described above we can raise a new generation of street trees which thrive in our urban environment whilst causing minimal conflict issues. By thinking creatively and being mindful of the many benefits streets bring, as well as the damage that can be caused by a lack of management or poor management, we can reduce the nuisance impact of existing trees.

A Special Type of Tree

Trees don’t only belong in forests and woodlands. They can grow and thrive among us, in our gardens, streets and public spaces, if we help them. The special type of tree I would like to champion in this blog is not of a particular species or genus, it’s of a place: The ‘street tree’.

There is no widely accepted definition of a street tree, but what I mean by the term is a tree that is growing within a public highway, including the carriageway, footpath or verge.

Good street trees can do a lot for us:

  • They help to improve air quality due to the production of oxygen and filtering of air-borne pollutants.
  • They add character and beauty to our engineered streets and create a ‘sense of place’.
  • They improve human health and well-being.
  • They encourage biodiversity by providing habitats and food sources for a variety of creatures.
  • They increase property values and promote investment and economic development.
  • They can help us adapt to a changing climate.

We shouldn’t think of roads as just for getting from A to B. They are places where we live and work. Successfully integrating trees into the built environment is, however, a challenge. It requires a cross-disciplinary approach throughout a long process, from design to delivery, to years of maintenance.

There are very few examples of good street trees on the Isle of Man. By ‘good’, I mean a mature tree that is: thriving in the urban environment without causing damage to surrounding infrastructure, resulting in conflict with neighbouring home, business owners, or users of the highway; well managed so that benefits are maximised and disbenefits are minimised; and, well suited to its setting in terms of canopy size and character.

If you know of a good street tree on the Isle of Man, we would love to see it. You can send it to us by email ( or share it to our Facebook page:

What is ‘Arboriculture’???

If you find yourself talking to someone you don’t know at a Christmas soiree, a common ice breaker you often hear is the innocent question ‘So, what do you do?’. My answer (an Arboricultural Consultant) often comes with a standard response and follow-up question: A what?! What’s that then?

So, what is arboriculture? defines arboriculture as the cultivation of trees and shrubs. That’s nice and simple, but maybe a bit too simple. defines it as the branch of horticulture concerned with the planting, growth and maintenance of trees. I wonder if the pun was intended.  I would disagree that arboriculture is a subdivision of horticulture. This definition tells you a bit more about what might be involved, but nothing about the purpose of the endeavour.

The Collins Dictionary ( defines arboriculture as the cultivation of trees or shrubs, esp for the production of timber. I would say that timber (wood) is more commonly a by-product than the purpose itself. goes with the cultivation of trees and shrubs especially for ornamental purposes. We’re getting closer, but what about managing trees for other purposes which don’t relate to aesthetical benefits, such wildlife conservation, heritage preservation and ecosystem services?

Modern arboriculture is obviously more difficult to define than I had first realised.

The main professional body for arboriculture in the British Isles, the Arboricultural Association, has recently defined the term as

The science and practice of the cultivation, establishment and management of amenity trees for the benefit of society.

‘Amenity trees’, in this context, means the trees that deliver environmental, social, and economic benefits for society. This inevitably means that arboriculturists are concerned with trees that are near people.

There are many different roles and careers which require knowledge in the field of arboriculture, including nursery workers, grounds maintenance staff, tree surgeons, (local government) tree officers, consultants, researchers, trainers, and policymakers.

There are close connections and links between arboriculture and other tree-related and environmental professions and disciplines, such as woodland management, forestry, horticulture and wildlife conservation. However, despite some overlaps, arboriculture is a profession in its own right, distinct in many ways from these other sectors.

Perhaps its easier to tell people that I’m a professional tree geek.

Applications For Tree Work – My Top Tips

I have mentioned in previous blog posts that until recently I was a tree officer at DEFA. That meant that every year I reviewed hundreds of applications to undertake tree work. Since I have been working for Manx Roots I have helped quite a few people with their tree applications, which means I have now seen the process from both sides. Most people don’t like filling in forms. This is usually because they either can’t be bothered with the hassle or aren’t sure of the answers they’re supposed to give. Regarding the former, DEFA have tried to make the process as simple as possible. You can now apply online, which means you can apply from your mobile phone whilst waiting for a bus! When it comes to knowing the answers to give, this is where I thought I may be able to offer some advice. If you can explain clearly and concisely what you want to do, why you want to do it, and provide the right supplementary information, your application is more likely to be processed in good time and is more likely to be approved.

Your first port of call should be DEFA’s guidance notes which contain lots of useful information, but here are some additional tips.

Empathy is the capacity to understand or feel what another person is experiencing from within their frame of reference, that is, the capacity to place oneself in another’s position. By understanding what the relevant legislation (Tree Preservation Act 1993) is trying to achieve, and by definition, DEFA and its tree officers, you will be better placed to make your application. So, keep in mind that legislation exists to preserve the amenity value provided by trees. The tree officer’s assessment weighs up the amenity value of tree against all your reasons for wanting to remove it.

Since the reasons for removal are so important, take the time to communicate your concerns clearly. For example, I commonly see and hear people saying, ‘that tree is too big’. If there is a rule about how big trees are allowed to be, I wish someone would tell me what it is! What you need to communicate is the problem the tree’s height (or spread) is causing, and who it’s causing a problem to. What people usually mean is ‘the canopy of the tree is casting an unreasonable amount of shade over my garden’, or ‘the tree is overbearing and is causing me significant apprehension due to its size in relation to my house’. Imagine there is an annoying child sat next to you whilst you’re completing your application who is tapping you on the shoulder asking why? Why? Yeah, but why? Drilling down into the reasons for removal will help the tree officer better understand your complaint.

It is important that tree officers properly understand the reasons for removal, but also that they can, where required, validate the reasons for removal. Statements such as ‘the tree is unsafe’, ‘the tree is damaging the drains’, or ‘the tree is causing structural damage to my property’ need to be verified; tree officers can’t just accept the applicant’s word for it. Consider how you can provide evidence to support your argument. For example, if you believe a tree is unsafe because of an obvious defect, try taking photos of the defect and taking detailed measurements; if the tree is damaging drains or causing structural damage, include details of surveys undertaken by relevant technical specialists.

As well as being an effective means of providing evidence of defects, photos are also useful for showing the tree in its context. Remembering that ‘amenity’ value is the most important factor in the tree officer’s assessment, photos can also be used to show the various public and private viewpoints of the tree. If the tree officer can assess the following attributes of the tree from your photos, it is very likely that your application will be assessed without a site visit, and will therefore be processed much more quickly:

  • The size of the tree
  • The importance of the tree in the local landscape and/or street scene
  • The suitability of the tree to its setting
  • The aesthetic form of the tree

So, as well as taking the obvious ‘photo of the tree’, try taking a little walk down the road and taking a photo of looking back at the tree in the wider landscape. If you walk 50 metres down the road and can’t see the tree, take the photo anyway and explain that’s the case. Remember though, that you will also need to accurately describe where you took the photo from.

If you’re able to, annotating the photos in free ‘paint’ or photo editing software can also be really helpful, especially if there are other trees in the visual field and it’s difficult to tell which one you’re talking about.

The more information you can provide by doing these things, the more likely it is that your application will be processed in good time and be approved.