Quick answer
Trees grow by producing new cells at specialised growing regions. Shoot and root tips extend the tree, while a ring of cambium beneath the bark adds new wood and inner bark, increasing the diameter of trunks, branches and woody roots. Growth depends on light, water, carbon dioxide, mineral nutrients, temperature, genetics and the condition of the surrounding ecosystem.
Key points
- Height growth comes mainly from buds and shoot tips, not from the base of the trunk.
- Trunks become wider when the vascular cambium produces new xylem and phloem.
- Roots and leaves exchange resources: roots supply water and minerals, while leaves supply sugars.
From seed to seedling
A seed contains an embryo and stored resources. When temperature, moisture and oxygen are suitable, germination begins. The first root, or radicle, grows into the soil, followed by the shoot. Early leaves may be seed leaves, called cotyledons, before the plant develops its characteristic foliage.
A seedling faces intense risks. It may dry out, be eaten, become shaded or fail to establish contact with suitable soil fungi. Those that survive begin allocating carbon to both above-ground light capture and below-ground water and nutrient capture.
How shoots make a tree taller
At the tip of each active shoot is an apical meristem. It produces new stem tissue, leaves and buds. A terminal bud extends the main axis, while side buds can form branches. Hormones help regulate whether side buds remain dormant or begin growing.
A nail fixed into a trunk does not rise as the tree gets taller because the existing trunk does not stretch upward. New height is added near shoot tips. The nail may become embedded as the trunk widens around it, which is one reason metal should not be left in trees.
How trunks and branches become thicker
The vascular cambium is a thin, continuous layer of dividing cells between wood and inner bark. It produces secondary xylem toward the centre and secondary phloem toward the outside. The accumulated xylem becomes wood. Seasonal differences in cell size and wall thickness can produce visible growth rings.
As diameter increases, the original outer tissues cannot stretch indefinitely. A cork cambium forms protective bark. Bark reduces water loss, buffers temperature changes and provides a physical barrier, although cracks, pores and wounds still permit gas exchange and can provide entry points for organisms.
How roots grow
Root tips contain meristems protected by root caps. Fine roots explore soil pores and form root hairs that greatly increase absorbing surface area. Many trees also associate with mycorrhizal fungi, whose hyphae can extend into soil volumes that roots alone would not reach efficiently.
Root systems respond to oxygen, moisture, soil strength, obstacles and nutrient patches. They commonly spread laterally well beyond the trunk and may extend beyond the crown. Deep roots can occur where soil permits, but many active fine roots remain relatively close to the surface because that is where oxygen and decomposing organic matter are abundant.
How leaves support growth
Leaves capture light and take in carbon dioxide through stomata. Photosynthesis produces carbohydrates. The tree uses these immediately, transports them through phloem, or stores them as starch in roots, stems and other tissues.
Growth is not constant. Temperate trees often flush in spring, slow during drought and enter dormancy in winter. Tropical trees may respond more to wet and dry seasons. A tree can also redirect growth after damage, producing new shoots or sealing off injured tissues.
What controls growth rate?
Species differ greatly. Some pioneers grow quickly in strong light but have shorter-lived wood and leaves. Other trees invest in dense wood, durable foliage and chemical defence, often growing more slowly.
A favourable site cannot remove genetic limits, and good genetics cannot overcome severe drought, compacted soil, root damage or persistent shade. Tree growth is the outcome of inherited strategy and local conditions.
Frequently asked questions
Do branches move upward as a tree grows?
Branches usually remain at roughly the same height on the trunk. New trunk and crown growth occurs above them, although branches may thicken, droop, break or be shed.
Can a tree grow after losing its top?
Many species can form a new leader from a side branch or dormant bud. The resulting structure may be weaker or more complex, depending on the damage and species.
Why do trees stop growing taller?
Hydraulic limits, wind exposure, temperature, carbon balance, age-related changes and species genetics all constrain height. There is no single universal stopping mechanism.
Related Nature9 guides
- How to Identify a Tree: A Beginner’s Step-by-Step Guide
- How Long Do Trees Live?
- How Do Trees Transport Water From Roots to Leaves?
- How Tall Can Trees Grow?
Sources and further reading
- Forest Research: Tree roots and trenching
- Science: How mycorrhizal associations drive plant populations and communities
- Royal Horticultural Society: How to grow trees
Information is presented for general education. Tree health, structural safety, protected wildlife and regulated plant-health problems may require qualified local advice.