Life cycle of a tree: How trees grow
Rachel Hoskins (Content editor)
How does a seed become a tree? This might perhaps seems like a huge journey, so we’ve broken down the different stages in a tree’s life – from seed to snag.
A seed is essentially a method of reproduction used by trees for millennia to ensure the next generation of trees can exist. Over time, seeds have evolved into different sizes and shapes so they can be effectively dispersed by wind, water or animals. All the resources a seed requires to survive independently until it reaches a safe place to grow are contained inside.
Credit: Adrian Infernus
Tree seeds are transported by wind, water, or in animal droppings.
How seeds become trees
Sprout (germination)
Once a seed has found the right conditions, it must secure itself. The first root breaks through the seed, anchoring it and absorbing water for the plant developing inside. The next stage in germination is the emergence of an embryonic shoot.
This shoot pushes up through the soil, with leaves either poking above ground or rotting underneath as the rest of the shoot grows above.
Seedlings
A shoot becomes a seedling when it is above ground. This stage is when trees are most at risk from diseases and damage, such as deer grazing.
Sapling
A tree becomes a sapling when it is over 3ft tall. The length of the sapling stage depends on the tree species, but each sapling has specific defining characteristics:
Flexible trunks
Smoother bark than mature trees
The inability to produce fruit or flowers.
Trees with exceptionally long life span (such as yews and oaks) remain saplings for much longer than shorter-lived species (like silver birch and wild cherry).
Mature tree
A tree becomes mature when it starts producing fruits or flowers - this is when the tree is at its most productive. How long it will remain productive depends on the species.
A typical English oak tree starts producing acorns at around 40 years old, peaking in productivity around 80-120 years. In general, Oaks, can be productive for 300 years, then rest for 300 years before moving on in their life cycle. In contrast, rowan starts producing berries after around 15 years, and by approximately 120 years it is already at the end of its life.
The fruits from these trees are dispersed and the life cycle repeats, but that’s not the end of a tree’s journey.
The trees we see in the wood have come a long way to get to that size.
Ancient trees
The next stage of a tree’s life comes when it passes beyond maturity and is older than trees of the same species: it has become ‘ancient’. Depending on the species, a tree might be called ‘ancient’ when it is only aged in its early hundreds (such as Rowan) or when it is thousands of years old, like the Yew. This means we cannot define ‘ancient’ trees solely by age. Instead, we look for key characteristics, like a small canopy and a wide trunk that is likely to be hollow - both of which show characteristics of ‘age’.
Credit: Manuel Sardo
Dead-wood hosts so much life - look out for bored holes and fungus!
Decaying tree (snag)
A snag is a tree in the final stages of life. It can be either a dead-standing tree or a dying tree. The tree’s life might be coming to an end, but its usefulness to wildlife is only just about to peak:
Dead-wood provides specialist homes for insects as well as fungi.
Those insects are a food source for birds, bats, and other small mammals.
These creatures take advantage of hollows or holes in the tree for shelter.
In turn, these smaller residents are food for larger mammals and birds of prey.
Dead and decaying trees are a vital part of biodiversity within woodland - that is why we leave plenty on our sites. Ultimately, removing dead-wood from woodland hinders an important part of its biodiversity.