You may be interested in Cultus Arborum by Anonymous, a newly released book, available via Project Gutenberg:
Phallic Tree Worship.
A DESCRIPTIVE ACCOUNT OF
Phallic Tree Worship
Legends, Superstitions, Usages, &c.,
Origin and Development
Eastern & Western Nations of the World
FROM THE EARLIEST TO MODERN TIMES;
WITH A BIBLIOGRAPHY OF WORKS UPON AND
REFERRING TO THE PHALLIC CULTUS.
From the preface:
THE present volume forms a companion to three already issued on “Ancient and Modern Symbol Worship,” denominated severally, “Phallism,” “Ophiolatreia,” “Phallic Objects and Remains,” and “Tree Worship,” they all form parts of one whole, and constitute a Series on the various forms and phases of what is known as “Phallic Worship.”
The subject is an extensive one, and there still remain sections of it which have not yet been dealt with, but which may be exhibited in future volumes. Although in the compass of the present work it has been impossible to treat the subject in anything like an exhaustive manner, a great deal of matter has been incorporated in its closely-printed pages which, attentively perused, will enable the reader to form a just opinion of what is included in the title.
At the end of this volume we have endeavoured to give the student of Ancient Faiths a Bibliography of works on or connected with Phallism.
Being the first attempt of the kind, omissions will doubtless be found, although there are nearly five hundred references given, yet even as it is, it will prove of great use and advantage to those making researches. It is divided into two classes—Phallic works, and books bearing more or less upon the subject.