Plant Index

A modern reference to temperate woody plants

The site

Trees and Shrubs Online is the International Dendrology Society’s ambitious project to create a modern, web-based encyclopaedia of woody plants hardy in the temperate parts of the world. The website was launched on a core of data formed from the full text of Bean’s Trees and Shrubs Hardy in the British Isles and of New Trees, making these seminal texts freely available to anyone, anywhere with an internet connection.

The long-term aim of the project is to renew these texts entirely, creating a fresh body of information for the twenty-first century that will make this the pre-eminent resource for anyone interested in trees and shrubs. The day to day project management, including editorial oversight of all new text, is the responsibility of the Editorial Team.

The text

Currently, the bulk of the text is derived from two sources. The 'Bean' text is from the Eighth Edition, the last to be published, which appeared in four volumes during the 1970s, along with the Supplement, published in 1988. New Trees was published in 2009 and sought to cover all the new introductions to cultivation from the period from the Eighth Edition to c. 2005.

Bringing all entries up to date is a large, complex, and long-term project. Some major genera, such as Rhododendron and Quercus, will need to be published incrementally, while others will be revised in full as funding becomes available. Many groups have already been revised (see Completed Groups), and an international team of authors is constantly at work preparing new entries.


Trees and Shrubs Online has been made possible by the International Dendrology Society, a truly international organisation with c. 1500 members in 50 countries. Since its inception the IDS has been dedicated to its charitable aim of advancing the knowledge of woody plants around the world. The idea for TSO was born out of the success of New Trees, itself an IDS project, and since the website’s launch the IDS has worked to raise funds to support the project’s ongoing work.

These efforts are now being rewarded by the tens of thousands of unique visits to TSO every month, from countries all around the world, and everyone involved in TSO looks forward to seeing these figures increase further.

TSO logo Sponsorship

May 2024: Trees and Shrubs Online relies on generous donations to meet its core costs and sponsorship to enable new text to be researched, written, edited and published. The project is indebted to the many individuals, organisations and charities that have contributed generously to our aim of disseminating new, high-quality information for free, for everyone. We are delighted to have recently received sponsorship to update the accounts of Hovenia, Paliurus and Ziziphus, three related genera in the buckthorn family (Rhamnaceae), together with Ailanthus, Leitneria, Picrasma, Melia and Symplocos.

The TSO team would be delighted to hear from anybody interested in supporting our ongoing work. We are particularly keen to secure funding to complete the ongoing revsion of the genus Acer, and to provide urgently-needed accounts of up-and-coming genera such as Lagerstroemia and Heptapleurum (Schefflera) for which very little information is currently available to gardeners. To enquire about these or other sponsorship opportunities please write to

TSO logo Recent publications

May 2024: Many new accounts have been published on the website in recent weeks, including Parrotia and several of its close allies in the Hamamelidaceae; Distyliopsis, Distylium, Parrotiopsis, ×Sycoparrotia and Sycopsis, together with an article covering novel hybrids of Distylium × Parrotia.

We are delighted to also be able to announce the publication of new accounts of North American maples (Acer spp.) including Section Rubra (A. rubrum, A. saccharinum and their hybrid A. × freemanii); Section Acer (the so-called sugar maples, A. saccharum and its relatives), together with the A. glabrum and A. negundo species complexes, the big leaf maple A. macrophyllum and the sole North American member of Series Palmata, the vine maple A. circinatum.

A list of all groups fully revised to date can be found on the Completed Groups page; this is updated whenever a new account is published.

Annual Report 2023

The TSO Annual Report for 2023 is available as a PDF for download.