Oak responds very well to thinning and will develop and build a crown if other trees do not crowd it. Both species begin to yield seed between the ages of 35-50, and oak coppice shoots can produce acorns 20 years after the stools are cut. Most prolific seeding occurs when the trees are 80-120 years old depending on site and climatic conditions. Seed is not produced prolifically every year, rather at intervals of 3-4 years for pedunculate oak, and 4-5 years for sessile oak. These seed years are termed 'mast' years, and seed produced between mast years is often poor, or absent altogether.
Ash, like the oak, is frost tender and light demanding. It regenerates prolifically, coppices freely and grows well in mixtures with oak, beech and sycamore. Ash grows quickly as a young tree with the growth peaking at age 20-25 years, stabilising at 40-45 and slowing to a minimum at 60 years and beyond. Seed production follows a similar pattern, with the first good crop of winged ash 'keys' coming at age 25-30 reaching a maximum at 40-60 years. The production of keys is not cyclical and good seed is produced in most years. Ash seedlings can withstand moderate shade but the growing tree is light demanding requiring overhead light and side shelter. Unlike oak it will not respond well to thinning if the crown has been restricted by competition. Ash is susceptible to frost damage, which causes forking in the mature tree and bacterial cancer which leads to degradation of the stem. In 2012 the ash disease Chalara faxinea was found on recently planted ash trees near Carmarthen. This fungal infection has now been found on mature trees near Ferryside. It is likely that this disease will eventually infect many of our ash trees.
Birch is slower growing and appears more suited to the poorly drained peaty soils of the Welsh uplands. Birch is extremely frost hardy and tolerant of exposure. It acts as a soil improver and the leaf litter reduces soil acidity. Young trees coppice freely and will usually recover from fire damage by producing new basal shoots. Young trees are vulnerable to browsing damage by farm stock, deer and small mammals. Birch produces large quantities of seed from a young age. It is light and airborne which enables it to colonise bare sites readily but it struggles to compete with existing ground vegetation except heather. Birch is a fast growing, short lived species, growing rapidly for the first 20 years reaching maturity at 40-50 years and slowing to death at 60-80 years. Areas of pure birch have the tendency to self-thin and do not respond well to thinning operations after canopy closure.
Beech is often associated with alkaline soils, but it will tolerate a wide range of soils and sites. It regenerates freely under the canopies of other trees and is often found in dense groups growing very slowly in extremes of light and nutrient competition. Seeding is also poor under a closed canopy, with little seed produced before the tree is 60 years old, sooner in an open grown tree. Production of seed reaches a maximum at age 80-140 and seeding may continue until the tree is 200 years of age. Mast years occur at irregular 5-15 year intervals and are believed to be associated with warm dry summers. Because of its need for the shelter of other trees and frost tenderness beech is not an ideal species for planting on open ground. It is better as an understory crop. It responds well to thinning, providing the crowns are big enough to recover. Young beech tends to hold its leaves during the winter which along with its shade bearing qualities and ability to withstand exposure make it ideally suited to shelter belts and windbreaks. Planting of beech in large quantities is not recommended as it suffers from a variety of fungal and bacterial diseases. It is often attacked by grey squirrels which strip the bark, causing serious timber defects and opening wounds for invasion of bacteria and fungi.
Sycamore will survive on most soil types but prefers deep well drained soils over chalk or limestone or acid brown earth. It is moderately susceptible to frost damage. Sycamore coppices well and regenerates freely, growing rapidly in the first 25 years of its life. It is often found in mixture with wild cherry, beech and ash or as a single species. Sycamore responds well to regular thinning to keep the crown deep and the growth vigorous. It is longer lived then other maples reaching maturity at 75+ years and can live well into its 100's. Grey squirrels will strip the bark and damage to the tree and timber can be significant if uncontrolled. The invasive nature of the regeneration can stifle the growth of other saplings particularly oak, and mature trees cast heavy shade which suppresses ground flora. It should not be introduced into native broadleaf woods where it is not already present.
Alder is a useful nurse to oak on heavy soil, coppices well, is hardy to frost and is deep rooting and wind firm. These characteristics make is a useful tree in shelter belts particularly as it is not that palatable to grazing animals.
Alder seedlings require moisture to establish, so regeneration is only successful in areas that remain damp through the spring and summer months. Growth is rapid for the first 20 years with maturity reached at 30-40 years. Growth is negligible at 60 years and above. Planted alder also does well on drier sites.
Wild cherry regenerates in the wild from seed and from suckering from parent trees. It grows rapidly on weed-free open sites to reach maturity in 55-65 years. Cherry sometimes dies for no apparent reason, followed by decay of the timber. Trees should therefore be kept vigorous by regular thinning carried out during the summer to minimise the chances of disease.