He left Toulouse around 1232 when the Cathars re-asserted themselves and university professors stopped being paid. He fled to the University of Paris, where Roger Bacon heard him lecture. It was this time in Paris that gave him his surname: he explains it is from the Rue Garlande in the neighborhood of the University.
There are over two dozen of his writings known (there are a few titles we know of, but have no extant copies). One was his Dictionarius (shown here), which was not a dictionary as we know it, but a textbook that attempted to teach Latin to French students at the University of Paris. Some credit Garland for the origin of the modern word "dictionary."
Besides works of instruction, he wrote poetry such as the Epithalamium beatae Mariae Virginis (“Bridal Song of the Blessed Virgin Mary”) and his account of the crusade against the Cathars, De triumphis ecclesiae (“On the Triumphs of the Church”). His hostility toward heresy was extended to Jews. To quote an author who wrote about this topic:
Although he never denied the possibility that conversion to Christianity could redeem the Jews, he thought it unlikely they would come over to the Catholic faith or remain steadfast in the religion. His invective was extreme by the standards of the time but was influential in that it appeared in many of his pedagogical works for adolescents and young men at the universities. [Journal of Medieval History, Vol.48, Issue 4]
Despite his time in France, his numerous writings were very popular in England, and were printed and re-printed in the 14th and 15th centuries.
Curiously, there was a second John of Garland who lived and wrote about the same time; this one was a music theorist, and will be our next topic.