Our woody collections are held in two main areas of the garden, the South Arboretum and the West Arboretum. An arboretum, from the Latin ‘arbor’ (tree) is, literally, a place where trees grow. Our arboreta cover approximately three-quarters of the garden and comprise over 700 trees and shrub species from across Europe, East Asia and the Americas. Most of the collection was planted in the late 1960s, when the garden relocated from Ballsbridge, which is relatively young in arboretum terms, though some have attained fairly mature stature in the fifty years since. Additional specimens have been added to the collection over the years.

Many of the trees and shrubs in our collection connect us to their far-flung wild origins around the world provide living woody material for scientific research and help worldwide conservation efforts, while native species also provide familiar refuge for small mammals, birds and insects. Their beauty and stature provide great pleasure the whole year round.

The environment of the arboretum floor also provides the perfect habitat for many more plant species which time their flowering according to the changing light levels of the seasons under the canopy.

Favorite Trees

Indian Horse Chestnut

The Indian Horse Chestnut (Aesculus indica) is c. 50 years old is a favourite in the South Arboretum. It is from the Horse Chestnut (Hippocastaneaceae) family and is native to the north-western Himalaya. It starts to flower in late May and continues through June with a profusion of pale pink ‘candles’ of white and pink flowers with a yellow centre which decorate the rounded crown. It has beautifully formed palmate leaves of seven leaflets which are a rich green throughout the summer, often turning golden in Autumn. Like the common horse chestnut (H. hippocastanum), it produces conker-like fruits but in spineless seed capsules. It is always hugely anticipated by the garden team and is a valuable source of pollen and nectar for bees.

Californian Redwood

The majestic Californian or coast redwood (Sequoia sempervirens) is the oldest and tallest living tree species on Earth, the tallest being known to measure 116 m tall and 9 m in diameter.  A member of the cypress family (Cupressaceae), it is native to a small area along the Pacific coast of south-western Oregon and north-western California. Redwoods thrive in the humid conditions of this part of the US and also grow well here in Ireland. The redwood is the tallest tree in our arboretum but is still a long way off full maturity, which could take another three hundred years! It has a long straight trunk rising tall into the sky and which flares elegantly at the base. Quite apart from the graceful form of the trunk, it’s beautiful cinnamon-coloured bark has a special function: it is relatively soft and spongy and is heat and fire resistant, a defense against the many forest fires experienced here. When the bark peels it provides a perfect substrate for some of the orchids in our Stove House. In the wild, this tree has suffered huge loss in numbers because of logging for its valuable, rot-resistant wood and is currently a protected species in a number of Californian state parks and the dedicated Sequoia National Park. Because of its beauty and fascinating history, it is another favourite tree in the arboretum.

Caucasian wingnut

The Caucasian wingnut (Pterocarya fraxinifolia) is in the Walnut family (Juglandacea). It’s common name is derived from its Genus name which comes from the Greek words pteron (wing) and karyon (nut). The specific epithet fraxinifolia, describes the appearance of its leaves (folia) which look similar to some ash (Fraxinus) species. In early summer very attractive long greenish catkins appear which carry the developing nutlets, providing a touch of decoration in the West Arboretum.

Foxglove Tree

The Foxglove Tree (Paulownia tomentosa) is a fast-growing native of China, which has now naturalised in northern USA. It is planted on an area of lawn at the southern-most boundary of the garden, where in late Spring-early Summer its spectacular clusters of mauve tubular flowers fill the air around it with a rich vanilla scent and it is a beautiful sight. However, in many gardens it is grown not for its flowers, but for the architectural interest provided by its roughly heart-shaped leaves, which, if the plant is coppiced (cut to the base) each year, will quickly regrow shoots with larger than normal leaves.


The arboretum is also home to many shrubs of scientific and conservation interest while adding extended seasonal interest, habitat and forage for pollinators.

Looking good this autumn...

No matter how many autumn seasons one has experienced, the colours in the garden at this time of the year never cease to surprise and delight. Trees can really come into their own this time of the year the trees, and the deciduous species, those that lose their leaves in winter, can truly sparkle in the autumn sunlight. Here is a selection of some of our colourful canopies…