We often hear how trees contribute to the health of our planet and its climate. Frequently the discussion focuses on forests, their destruction, protection and creation. However, we can all make a difference by planting trees in our own garden.
There is a wealth of research on how trees improve the urban environment. They provide shade, help manage our city temperatures and some species will reduce noise or pollution. On a global level it is their ability to absorb and store carbon as they grow.
But are some trees greater carbon stores than others? Barcham Trees now publish eco tree tags for all the trees they sell. Using research commissioned from Treeconomics and based on the familiar format used for rating the energy efficiency of appliances, each tree gets a rating from A to E. Fascinatingly they also tell us the rate at which the carbon is stored across the tree's lifespan and the point at which it offsets the carbon produced to grow, deliver and plant it.
Nervously, I thought I would look at the rating for some of my favourite trees which I often use in my planting designs. How would they score and would I need to rethink some of my choices? Luckily many, reflecting their similar garden-friendly dimensions, score a respectable C but the amount does vary from species to species. One of my favourites, the winter flowering cherry (Prunus "Autumnalis") will absorb 685kg of carbon across its lifetime, almost 30% higher than another go-to tree Amelanchier "Ballerina" at just 530kg. Both fall within Group C, but Autumnalis will offset its carbon footprint after just 12 months, whilst Ballerina takes a full three years.
As a simple rule of thumb, the larger the tree the more carbon it will store. Does this mean we should all be planting big trees such as the chart-topping Eucalyptus gunii, scoring A and storing an impressive 7,570kg? Well. as always, the answer depends on the space you have available. If it's for your average urban garden then the answer is no. Barcham points out that a tree needs to grow well and to its full size if it's to store the maximum amount of carbon. Another reason to make sure that your chosen tree is suitable for the conditions and space available.
I still feel comfortable with my favourites, but I have decided to bear in mind how a tree scores when including them in my designs. If I can achieve the desired effect with different trees, then their relative carbon scores will be a useful deciding factor.
For more information on their eco tree tags and how they were developed click here.
Today is Earth Day when across the world organisations and individuals come together to celebrate and "promote a healthy environment and a peaceful, just, sustainable world". The Washington Institute has published a score card highlighting four key areas of concern for 2015, so what can we do at home to help?
1. Make our outside spaces wildlife friendly
One in four species of birds, mammals, reptiles, amphibians and fish are on the verge of extinction or extinct. We can do our bit for our local species by making our gardens or outside space more welcoming for wildlife. The RSPB campaign Make a Home offers lots of excellent tips for making your space wildlife friendly.
Even the smallest balcony can offer food and shelter for birds and insects. Wildlife friendly does not have to be untidy, a formal pond will attract wildlife and many flowers adored by the most discerning gardener are equally loved by bees and other insects.
2. Use your harvest
One person in six alive today is chronically hungry. I am not sure that the keenest grow-your-own enthusiast can solve this one but there are things we can do to help reduce food waste and local charities. Maybe you have fruit trees but are unable to pick the fruit or it's simply too much for you to use. Locally Northfield Ecocentre run Urban Harvest which collects unwanted fruit and vegetables and redistribute them to local charities, schools and a local Community Café, the rest is used to create lovely juices and preserves. Thousands of tonnes of fruit goes unused in our city gardens so why not help reduce the waste. Or if you haven't got any surplus why not help by volunteering with the harvest.
3. Buy local and recycle
Between between 1970 and today 160 billion tonnes of carbon dioxide have been released into the atmosphere, that's more than in the previous 200 years. We can all help by buying plants and sourcing our hard-landscaping materials locally. There are many small plant nurseries which offer a larger and more interesting range of locally grown plants than you will find in the big Garden Centres. When re-designing a planting scheme or garden I always try and re-use or recycle what I can. If it isn't wanted or doesn't fit with the new scheme then there is nearly always someone who can use it, try advertising on your local Freecycle or Streetlife.
4. Celebrate our green spaces
The final scorecard fact is that the Earth's population has almost doubled since 1970, and in the same period the share of cropland per person has almost halved. I had to think laterally on this one as I am not sure that I can help with either of these : ) But the message I think we should take is how lucky we are to have public and private green spaces to enjoy. We should celebrate this and ensure that we are making the most of whatever outside space we have - every little bit of green we can create in our cities helps reduce pollution, support wildlife and provides enjoyment not only to us but everyone one who passes by - guess which is my outside space?
If you would like to celebrate Earth Day but like me are at work today, then why not go along to the free Birmingham Botanical Gardens Earth Day at the Gardens on Saturday 25th April. This year it also commemorates the 70th Anniversary of the end of World War II highlighting the role of Victory Gardens from their design, propaganda and the impact on gardening today.