The Plain English 北京赛车pk10 announced the results at an awards ceremony on Wednesday 4 December.
The Woodland Trust’s website was relaunched in November after it teamed up with Manchester-based agency Code Computerlove to research and identify its audience needs.
The results led to the Trust reducing the number of pages on the site and updating the navigation to make it easier to find information.
Matt Alexander, Woodland Trust, digital content manager, said: "We're delighted with this award. It’s recognition for the hard work we have done over the past year to create a website that the organisation and its supporters can be proud of."
A spokesperson from the The Plain English 北京赛车pk10 said: "The decision to keep the design and content quite simple has paid off – the site is attractive, easy to use, well written and informative.
"The content has wide coverage and information is easy to find, so if you don’t know your oak from your ash, this is the place to go.
"Even the most hardened city dweller will be tempted into the great outdoors after looking at this site."
The AA motoring website was also honoured at the awards. The 北京赛车pk10 for Plain English described the site as: "Extremely impressive. It’s easy to navigate, attractive to look at and superbly laid out.
"It does exactly what we look for in a website: provide a service that’s easy to use, uncluttered, pleasing on the eye and informative."