The TCD herbarium was established in 1840; its nucleus was the personal collection of Thomas Coulter, the first curator. Coulter was a well-known early plant-collector/explorer best known for his work in Mexico and North America. From there come two of his best known finds, both of which were named in his honour; Coulter Pine (Pinus coulteri) and the highly attractive garden plant Romneya coulteri.
However, the Herbarium is really the creation of William Henry Harvey who was curator from 1844 until his death in 1866. Harvey, the son of a Quaker merchant from Limerick, and the leading phycologist of his day, was incredibly hard-working. He writes, "I rise at five a.m. or before it and work until half-past eight on the Antarctic Algae. Directly after breakfast I start for the College and do not leave it till five o'clock in the evening". His own hard-work combined with an ability to make and keep friends, including for example, Charles Darwin. This, together with his extensive exploration of Australia, North America and South Africa led to the accumulation of 100,000 specimens by the mid 19th Century. His achievements are all the more remarkable when it is recalled that at the same time as he undertook extensive plant-collecting Harvey wrote several books and that these were illustrated by over 900 of his own hand-drawn lithographic plates.
After Harvey's death the herbarium continued to accumulate material, notably that of A.F.G. Kerr, a medical graduate of Trinity College from Co. Leitrim, who was the first (and is still the most important) plant collector to work in the tropical forests of Thailand. The existing herbarium building was added as an annex to the School of Botany in 1910.
Prior to that, the Herbarium had been housed in very unsatisfactory conditions in No. 5 Trinity College. Henry Dixon, a noted plant physiologist, was responsible for seeing the School of Botany completed in 1907 and although he had no serious taxonomic interests he ensured that the Herbarium was built in 1910 with a grant from Lord Iveagh. Dixon also worked hard on curating the herbarium in its early days although he often referred to it as "that collection of hay". Despite these disparaging remarks, he clearly recognised the significance of an active Herbarium to the Botany Department. Unfortunately, few other universities in Britain and Ireland have proved as enlightened as only two (Oxford & Cambridge) have herbaria of comparable significance.
Webb (1991) shows that the largest collections of material in the Herbarium are from Europe, South Africa, Australia, South-east Asia, South America and North America; though all regions of the world, including Antarctica are represented. Since Webb's paper considerable expansion of the Herbarium has taken place; it's library is even better and is amongst the best of its type in Europe; the collections have been considerably expanded with a large number of modern collections from Thailand incorporated. The official designation of the herbarium in Index Herbariorum is TCD; this latter work also summarizes some of the information presented here.