Some trees and plants have deep roots that extend down into the depths of the soil, whereas other plants are more shallowly rooted. Read on to find out more about the diverse root systems of plants and trees and some examples of the different types.
The root systems of plants and trees are essential not just for stability but also for transporting moisture and nutrients for growth. Larger and thicker roots act as anchors, penetrating down and across the earth, while smaller fibrous roots absorb water and nutrients.
Deep rooted and shallow rooted plants: explanation
It is commonly thought that tree roots grow deep into the ground. According to new research, around 80 % of a tree’s roots are located in just the top 60 cm of soil and the majority of roots do not extend more than 2 m below the earth’s surface.
When we talk about deep rooted plants, we usually mean plants or trees with a root system that has tap roots, reaching deep into the ground. On the other hand, shallow rooted trees or plants tend to have a root system that extends laterally to provide stability and support. Heart-shaped root systems are a cross between the two and are stabilised by the size and weight of their root balls.
Examples of shallow rooted plants
Trees and plants with shallow roots usually have more laterally extending root systems and might be helpful when gardening in shallow soil or in containers. However, the roots of shallow rooted plants can extend far beyond the canopy and cause damage to nearby hard landscaping and foundations. Shallow rooted plants are also less stable in storms or gales. As a result, when planting, care must be taken to ensure that the future root system will not cause any damage as it matures and spreads.
Some examples of shallow rooted trees and plants include:
- Birch (Betula): birch trees are shallow-rooted, forming extensive root mats just under the surface.
- Ash (Fraxinus excelsior): the ash’s lateral roots spreads widely. However, due to the prevalence of ash-dieback disease (Hymenoscyphus fraxineus) in the UK, ash is not often recommended at the moment.
- Pear (Pyrus communis): pear trees have shallow roots, which should be considered when planting an orchard.
- Hydrangea (Hydrangea): hydrangeas are widely grown in the UK and thrive with our high levels of rainfall. As shallow rooted shrubs, they grow well in pots. However, plants with shallow root systems are often the first plants to wilt in a hot and dry spell.
- Willow (Salix): willows have shallow roots that can be invasive. They tend to grow well next to a water course or pond.
- Lavender (Lavandula): the drought-tolerant lavender produces a shallow root system, making it ideal for growing in containers or shallow beds and borders.
Examples of deep rooted plants and trees
Deep rooted trees and plants often have some taproots that extend into the earth. Taproots can provide a continuous supply of moisture by accessing the water table down below and also provide stability. Deep rooted plants are recommended for growing in free-draining and dry soils when watering is a concern. They may struggle in wet and waterlogged soils, resulting in rotting.
Some examples of plants and trees with deep roots include:
- Yew (Taxus): yews have taproots as well as a shallow root system and can be found all over the UK, particularly in churchyards where the yew trees are older than the buildings.
- Oak (Quercus): with their deep and widely extending root systems, oaks have proven to stand the test of time.
- Sweet gum (Liquidambar): Liquidambars are increasingly popular due to their autumnal foliage but can develop destructive shallow roots in addition to deep roots.
- Fir (Abies): belonging to the pine family (Pinaceae), firs have taproots that extend deep into the earth.
- Pine (Pinus): native to the Northern hemisphere, pines grow extensive taproots that provide stability.
- Dandelion (Taraxacum officinale): producing deep taproots, dandelions must be removed with their taproot intact.
- Roses (Rosa): climbing and shrub roses are notorious for their deep roots that can prove troublesome when transplanting.
- Californian lilac (Ceanothus): often grown for their dazzling blue flowers, ceanothus develop deep roots in search of moisture.
- Green alkanet (Pentaglottis sempervirens): although pollinators love it, green alkanet can be the bane of gardeners due to its deep taproot that regrows quickly if broken.
Roots are indispensable to the life of any plant or tree as they provide constant access to essential moisture and nutrients. For more advice on how to correctly water your plants, especially during hot and dry spells see our feature article.