There are currently over 300 trees in St Andrews Botanic Garden including a collection of more than 50 recorded champion trees. There are 6 British champions including a Koehne mountain ash and an apricot tree, 14 Scottish champions and 39 county champions. Many of these trees were planted after 1970 and are growing fast as a result of the microclimates purposefully created as part of the garden design.
The garden has a significant number of individual species collections including 111 varieties of berberis and 156 varieties of cotoneaster. Other collections include sorbus, rowan, rhododendron, honeysuckle (caprifoliaceae), heather (ericaceae), and rose (rosacea).
Geographical collections include groups of Chinese, Western South American and Sino-Himalayan plants. In 2012 a survey by Plant Heritage ('Conserving Cultivars', Sept 2012) identified 43 plants in the gardens rare enough to be threatened in cultivation of which 23 were cultivars unique to St Andrews Botanic Garden.
Themed areas within the garden include:
The Water Garden (established 1974-76) which is situated on sloping ground to the north of the rock garden and forms a centrepiece of the garden. It comprises a sequence of three cascades, stepping down into small ponds and terminating in a fifty foot pond, located on lower ground near the Kinness Burn. Water gathered at this location prior to the construction of the Garden, so the water garden is evidence of the designers working with and embellishing the natural topography of the site.
The Order Beds are laid out according to the Cronquist taxonomic system, with 134 plant families divided into five major groups in a triangular-plan bedding plan, radiating outwards from the earliest plants at the centre to the more recently evolved species at the furthest edges. Plants from the same botanical group are grown together to illustrate the characteristics they share, and to demonstrate evolutionary theory in flowering plants.
The Rock Garden (developed 1964-67) was inspired by the great rock garden at Edinburgh and the former rock garden at St Mary's College. The rock garden area has terraces, cliffs and scree slopes, interspersed with limestone pavement.
The Heath Garden is located in a sheltered area near the centre of the garden and contains a wide range of heaths, heathers and small conifers.
The Woodland and Rhododendron Garden covers a sloping and terraced bank of peat soil with pathways containing around 80 dwarf rhododendron species, trees and ericaceous plants.
The Glasshouses (established 1966-71) contain themed collections, with plants from temperate to tropical climates and covering a wide geographical range. The four main glasshouses, which were relocated from nearby Craigtoun Park in 1966, are linked by a corridor under glass to the north with succulents, cacti, alpines, Mediterranean species and an area housing some of the less robust rhododendrons. Educational facilities are housed within two of the glasshouses. There is also a herbarium with 10,000 specimens, a seed bank and a plant record database.
The rectangular-plan Herb Garden to the east of the glasshouses is more formal, set out on a Saltire Cross pattern.
There is a specimen conifer grouping in the Arboretum (Woodland Walk) located at the narrow, east corner of the garden.