An earlier thread (see Best time of year to trim hedgerow) raised the
question of hedgerow species and age. I remembered that Rackham had
covered this at some length in his splendid History of the
Countryside. The following much abridged notes may be of interest.

Rackham on Hooper's Rule
Dr Max Hooper (Pollard and others 1974) indicated that soil, climate,
management or planting of a hedge were less important than its age. He
surveyed the shrub and tree species in 227 hedges that could be dated
from records with ages ranging from 75 to 1100 years. He discovered a
degree of correlation between the species and the age. The number of
species was approximately equal to the age of the hedge in centuries.

Rackham comments that it is customary to use a sample hedge length of
30 yards and exclude under-shrubs such as brambles and woody climbers
such as ivy and ignore sub-species (he gives the example of differing
East Anglian elms). He provides a suggested list of species for
inclusion (page 195, 1995 edition).

Alder
Apple
Ash
Beech
Blackthorn
Briar
Broom
Buckthorn
Cherry
Cherry-plum
Dogwood
Elder
Elm - wych, English, East Anglian, Cornish etc, Dutch, Huntingdon etc
Furze
Guelder rose
Hawthorn - hedgerow and woodland
Hazel
Holly
Hornbeam
Lime - ordinary, pry
Maple
Oak - pedunculate, sessile
Pine
Plum including bullace
Poplar - aspen, black, white
Privet (wild)
Rowan
Sallow
Service
Spindle
Sycamore
Wayfaring-tree
Whitebeam
Willow - crack, white
Yew

He goes on to say that there are some regional variations -
Huntingdonshire and Lincolnshire hedges being predominantly simple of
1, 2 or 3 species, influenced by much Enclosure Act land (generally
only 1 species) and with few hedges pre 1700. The ancient countryside
of Devon and Kent mainly 5 plus species.

rbel