Hedges are popular fixtures in places like city parks and residential areas. However, you may not be entirely aware of the complexities of creating a successful hedge. For example, you may not know about the root structure of hedges.
Not all hedges have deep roots. How deep the roots of hedges grow depends on the type of plant you use. For instance, some hedges formed by laurel and boxwood shrub cultivars with fibrous root systems have shallow roots that spread laterally on the upper 12 inches (30 cm) of the soil.
This article will dig deeper into whether hedges need deep roots, the benefits and risks of having such, and what plants with deep roots can be used for hedges.
Do Hedges Need Deep Roots?
Hedges do not need deep roots. There are a few cases where hedges need deep roots, such as when the soil has poor moisture retention capacity or if the area they grow in is a slope requiring the shrubs to have a sturdy anchor.
Many hedges thrive with shallow root systems, even those built from drought-tolerant plants. Such plants don’t need much moisture from deep into the ground. However, they may seek water closer to the surface, requiring a substrate that holds moisture efficiently.
That said, some hedges have plants with deep taproot systems that can extend two feet (60 cm) or more below the surface. This is due to environmental conditions that make plants with deep roots more suitable for a hedge.
Below, I’ll go into more detail on the instances where hedges need deep roots.
The Soil Has Poor Moisture Retention Capacity
Sandy or coarse soil tends to drain water too quickly, leaving the plants with less time to absorb as much moisture as they need. Such an environment is more suitable for plants with deep roots as they can continue to absorb water deep below the surface.
However, even hedges with deep roots still need to be watered regularly to meet their water requirements. Otherwise, the remaining moisture in the soil may drain further down beyond the reach of the roots.
As a result, the roots may grow deeper down or laterally to search for more moisture from the ground.
Growing Hedges on Hills or Slopes
Water drains more quickly on hills or slopes than on flat land. As a result, hedges need deep roots to access enough moisture for as long as they can. In addition, the deep roots can help hedge plants gain anchor to prevent them from being uprooted due to soil erosion from heavy rain or gravity. The roots provide structural support to keep the plants upright and resilient to environmental factors like heavy rain and strong wind.
Conversely, the deep-rooted hedges can also provide support to hills or slopes by holding the soil in place through lateral roots branching out of the central taproot. These tiny roots can effectively reduce soil erosion.
Advantages of Hedges With Deep Roots
Although hedges don’t have to have deep roots, there are still several benefits to them.
It Allows More Efficient Moisture and Nutrient Absorption
As mentioned, hedge plants with deep roots can absorb moisture from deeper below the ground in case of drought. They’re also especially beneficial if your area has sandy soil and there’s no other (or at least more practical) way to increase its water retention capacity.
Deep roots can also give the plant better access to nutrients leached deep into the soil. Heavy rains or over-watering often push nutrients beyond the reach of shallow roots. Deep roots, on the other hand, can access them more efficiently for longer periods before they’re entirely lost.
It Can Prevent Strangling the Roots of Nearby Plants
Plants with laterally growing roots tend to intertwine with the roots of neighboring plants, whether they’re the same species or not. This can be even more troublesome for hedges where you grow plants in a row. Insufficient space and overcrowding can present several problems in a hedge. They can result in entangled roots that compete for moisture and may strangle each other, resulting in root damage and reduced moisture absorption.
You can eliminate this problem if your hedge plants have deep roots. While plants with taproots typically have lateral roots, their size and spread aren’t too significant to cause any physical damage to the roots of neighboring plants.
It Reduces the Risk of Damaging Underground Cables and Pipes
Deep roots grow downwards, reducing the risk of coming across underground cables and pipes. Some hedge plants with shallow invasive roots can twist around wires and pipes and damage them. As long as you keep your hedge with deep roots away from the location of your underground cables, wirings, or pipes, you can avoid the risk of the roots damaging them.
It helps to make a map of the location of sensitive underground structures when planning to create a hedge in your garden. A map can also help you determine a safe distance and shape for your hedge.
Disadvantages of Hedges With Deep Roots
Hedges can benefit from having deep roots, but there are also some disadvantages.
The Roots Can Damage Septic and Sewer Systems or Water Pipes
If you’re planning to grow a hedge or any large, woody plant in your home garden, you’ll need to find a safe spot. One important thing to consider is if the roots may damage any structures underneath the ground. The roots typically grow deeper into the soil and may pierce through some sensitive structures. Planting large shrubs with deep roots directly above septic or sewer systems can result in severe damage that will be difficult (and even costly) to fix.
Taller hedge shrubs or trees with taproots systems typically have roots that grow very deep — sometimes as deep as the shrub or tree is tall. They’ll be challenging to uproot, and it can be troublesome to fix damaged underground structures.
The Plants Will Be Difficult To Dig Out
It can be difficult to dig out plants with deep roots when it’s time to uproot your hedges to change your garden’s aesthetics. Older and fully established hedges may have roots extending several feet below the surface. Digging them out can be a problem.
Often, gardeners use herbicides to kill the remaining roots. However, if you plan to grow new plants in your garden, it may take several months or even years before the soil can be safe again, depending on the potency and mode of action of the specific herbicide you use.
Plants With Deep Roots Used for Hedges
Regardless of the disadvantages mentioned above, some gardeners may still prefer hedges with deep roots. As long as you consider all the precautions discussed, it should be safe to use plants with deep roots for a hedge.
If your location warrants hedge plants with deep roots, you can choose from the list of plants below:
Sometimes called mock orange, the orange jessamine (Murraya paniculata) is a common tree or shrub often used for hedges. It can grow up to 20 feet (6 m) tall, but most varieties grow only half that size. It can even be pruned aggressively to maintain a 3-feet (90-cm) height that resembles a boxwood hedge. However, unlike the boxwood with shallow roots, the orange jessamine has a deep taproot system with many fibrous roots spreading outwards.
Another common shrub often used for hedges is yew (Taxus spp.). The shrub has wide varieties and cultivars. Some have shallow roots, while others, such as the English yew (Taxus baccata), have deep roots that can grow several feet below the surface and penetrate even rocky substrates.
Note that as the plants get bigger with thicker foliage, the roots will also typically grow deeper into the ground to provide the plant with adequate nutrients, moisture, and structural support.
Above the ground’s surface, the hedge is pretty easy to maintain with regular pruning to keep it at your desired height and shape. However, underground, the roots can become too big, making them pretty challenging to uproot later.
This laurel variety (Kalmia latifolia) is typically found in dry areas or mountains, giving it the moniker ‘mountain’ laurel. It has a deep taproot system to adapt to the dry conditions and absorb as much moisture from the ground as possible. Its deep roots also provide the mountain laurel structural support.
Mountain laurel roots need cool soil so you may need to apply a few inches of mulch on the ground around the base of the plant during extremely hot summers.
Some hedges have deep roots, while others have shallow roots. It mainly depends on what kind of plants you use. Knowing the pros and cons of having deep roots can help you decide what plants to use for your hedge.
Deep-rooted hedges are suitable for gardens situated on slopes or if the soil has poor water retention. However, you need to consider the underground structures in your area that may be affected or damaged by the roots before choosing a location and plant variety for your hedge.