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The growing impact of tree diseases

The growing impact of tree diseases

A concern of mine for 2018 is the continuing impact of two, now common, tree diseases. The first is Chalara Ash Dieback – which was first identified in the UK in 2012, having killed up to 80% of all ash trees in some parts of continental Europe in the previous 20 years. The second is the Cameraria leaf miner – first recorded in Greece in the 1980s and first noted in Britain in 2002.

Chalara Ash Dieback is a fungal disease (now being called Hymenoscyphus fraxineus) that was first identified spreading in an asexual form, but now seems to be found spreading sexually, with fruiting spores appearing on the previous years leaf litter between June and September. I personally first noted it affecting trees in West Norfolk in 2015 – but it appears to have spread rapidly in the last three years and I now believe it is widespread in Norfolk and throughout East Anglia. I have been monitoring a young woodland shelterbelt near my home, which is approximately 50% ash, and by the summer of 2017 about 25% of the ash trees were dead and another 25% looked stressed (see photo). Nevertheless, some of the ash in this stand still appear entirely healthy – and experts do believe a proportion of ash trees will show resistance.

Having noted the spread of the disease and the apparent rapid decline of both young and old ash trees in Norfolk, I remain somewhat sceptical that a significant proportion of ash trees will survive – especially as the fungus has now been shown to be spreading sexually. This is likely to lead to new, perhaps more virulent, strains of the disease in coming years. (It is often forgotten that Dutch Elm Disease first became a problem in Britain in the 1920s and 30s, but it was the arrival of a more virulent strain that eventually decimated the British elm population in the 1960s and 70s).

The widespread loss of Ash trees in many of our landscapes will be quite catastrophic. Ash is one of our commonest trees – both in urban and rural settings. In many settings it is the dominant large hedge tree and it often forms a large proportion of mixed native woodlands.

A second ‘disease’ which is now apparently ubiquitous in southern and eastern Britain (but I have noted – perhaps not so much in western counties and Wales?) is the Cameraria leaf miner, that now brings an unseasonal ‘autumn’ to most Horse Chestnuts as early as late July. The easily recognised browning of leaves is caused by the larvae of the tiny moth Cameraria ohridella as they burrow inside the leaf.

Cameraria has generally been considered a cosmetic problem – but it stands to reason that if trees have their growing season curtailed three months early each year, that this will eventually lead to a decline in vitality. Anecdotally, during my travels in 2017, I noted many large Chestnuts showing obvious signs of significant stress, with large dead branches in the crown and strong evidence that they were in terminal decline. I am thinking that a critical point may have been reached with the trees relationship with Cameraria – and it is now well established that trees with the leaf miner seem more susceptible to other diseases such as Bleeding Canker (Pseudomonas syringae pv. Aesculi).

Although Horse Chestnut is not a native British tree, it is surely one of our finest and commonest large flowering trees. If we lost Chestnuts and Ash from our landscapes in coming years it would have a significant adverse impact on landscape amenity. Richard Morrish Associates haven’t recommended planting new Ash or Chestnut trees for more than 5 years now – and we have been looking at other species that can fill the gaps in our countryside – Acer, Alnus, Tilia and less commonly planted genera, such as Ostrya. But it will not be easy to replace Ash and Chestnut. 


Can we avoid a race to the bottom – please?

Can we avoid a race to the bottom – please?

Most practitioners seem very busy at present – and the race to try to provide the vast amount of new housing government says we need is certainly one reason for that. I understand the cost pressures on developers, but I am worried about the penny pinching that seems to be becoming common – especially in terms of landscape provision. It is a fact that spending some money on landscape provision gives a lot of ‘bang for the buck’. For a relatively small amount of money it can do so much to ‘finish’ a scheme – with obvious marketing and sales benefits.

However, landscape provision is so much more important than that. It was great to hear the feted architect Amanda Levete on Desert Island Discs a few weeks back. She said ‘As our lives become increasingly individualised there has never been a more important time to create outdoor public spaces. Its where relationships are formed, ideas are exchanged – and that leads to progress. We need to make spaces that belong to the public’. Facebook and Twitter cannot replace ‘traditional’ social intercourse. Never is this more important to consider than when creating new residential communities.

Landscape spaces are beneficial in so many ways – whether it is providing safe, comfortable recreation spaces, buffering air pollution, supporting local wildlife or simply providing amenity pleasure. But the basic goal of creating spaces for social exchange and community building is especially important. This is essential if we are going to create safe, healthy, happy and successful communities. Planning and delivering good landscape infrastructure is not a cosmetic optional extra. It is a fundamental element of urban design.

A flexible approach for changing times ...

A flexible approach for changing times ...

One of my new year resolutions is to try keep my website updated – my last blog was regrettably a couple of years ago! As we start 2017 there are uncertainties about the future economy, government policy making and the environment in which we work (the impact of new tree diseases is a particular landscape concern). The demand for new housing looks likely to keep the building industry busy in coming years. Regardless of economic conditions, it will be essential to keep standards of environmental design high in the current rush to meet needs. Future generations will not thank us for shoddy buildings or poor residential settings.

Consultant practitioners are going to have to remain flexible, well informed, and responsive to client requirements. This is something we certainly try to do at RMA, and if you are looking at this blog as a prospective client checking what services we provide – please don’t hesitate to give me a ring to chat through your requirements. We are always interested in developing a new approach! 

Aussies Caught Out !

Aussies Caught Out !

How to beat climate change? I have been thinking for some years if we are going to have milder winters and dry summers maybe some of the tougher Australian plants might have a future in the UK. However the short very cold snaps we have had in recent winters have caught out the Australians. Two years ago the cold virtually wiped out all Cordylines. Im not a great fan of them anyway – and their true home is really the sub-tropics. But this last cold snap in February 2012 has affected much tougher plants – even well established Eucalypts. In my garden I lost my Callistemons and Grevillea even when they were well wrapped up against the cold. Im thinking the relatively warm January (when they all sprouted soft new shoots), combined with a cold so intense it may have frozen the roots – probably did for them. It looks like they may not yet be the panacea for dry summers – unless you want to bring them in every winter!

Seasonal Changes

Seasonal Changes

Many people are talking about the 'early spring' and I have heard a whole range of reports of early flowering – bulbs, primroses, cowslips and all number of garden plants. What I think is even more surprising, and perhaps concerning, is trees and shrubs that have 'skipped' winter completely. I have seen oak and hazel that are still holding on to last years leaves in East Anglia - and they are still green. Ash in my own garden was green until the middle of December. If such mild winters become the norm, will our natives become semi-deciduous? If so I imagine this will impact on a range of phenological phenomena - bud burst, flowering, seed production and especially the relationships with invertebrates and other organisms that interact with trees. We need to monitor how tree and shrub species respond to these changes, as I am sure it will begin to influence management decisions. You can submit sightings to the Woodland Trust 'Natures Calender' site www.naturescalender.org.uk, if you are interested in contributing to a growing record of these seasonal changes.





Arboricultural Services in Virginia Water

Arboricultural Services in Virginia Water

I provided arboricultural services in double quick time for a client in Virginia Water this month. The planning authority requested an arboricultural survey and provisional tree protection plan before they would validate a planning application. The client wanted the application in as soon as possible. I undertook the survey of over 300 trees over a weekend, coordinated the tree protection specification with the rest of the design team, and submitted the finished documentation by Tuesday afternoon.
Planning authorities usually require a tree survey as part of planning applications – particularly where they consider trees have an amenity value in the wider landscape. Its always good to check with the authority prior to submission. However, if you are up against a deadline RMA will always try to meet your needs.


New Childrens Nursery

New Childrens Nursery

I was pleased to see that our client received planning consent for a new children's nursery near Cambridge at the end of December. Although the project architect had provided a clear summary of landscape issues in the initial information to planners, the authority had asked for a full visual impact assessment as the site adjoined the green belt. RMA provided a stand alone report with photo montage views as supplementary information to the planning application. For clients seeking to keep costs down, RMA can now offer a one-stop-shop for landscape related documentation for planning applications – arboricultural surveys, visual impact assessment and landscape design documentation.



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