There are 13 species of horse chestnut but none are native to Ireland. Mostly seen is Aesculus hippocastanum, a large statuesque tree adorned with large clusters of white flowers in May. In autumn the green spiky fruit crack open for a round brown nut to fall out. The brown nut is often called a conker.
Although the horse chestnut is too big for all but the largest of gardens, there are some othe smaller growing species that are more shrub like in growth.
A pink flowered A. x carnea is sometimes seen and used as a street tree.
Horse chestnuts are not eaten. The edible chestnuts come from a completely unrelated tree called Castanea sativa.