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How Deep Do Grass Roots Grow?

How Deep Do Grass Roots Grow?

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Sydney Bosque
Latest posts by Sydney Bosque (see all)

The depth of roots in your lawn is critical for overall health. Deep roots help grasses survive stressful conditions, which is why a large part of lawn maintenance is directed at creating a deep, healthy root system.

How deep do grassroots grow? In healthy soil, turf grasses will generally have a root depth of 6”–2’, and their root systems will be long, white, and dense. However, root depth is greatly influenced by the underlying soil health and irrigation schedule.

Ultimately, the depth of grassroots depends on your lawn care maintenance schedule. There are many ways you can encourage deep, healthy root systems.

Why Are Deep Roots Important In Lawns?

Roots are the conduit through which water, nutrients, and oxygen are transported into a plant. The deeper this conduit reaches, the more resources the plant has at its disposal.

When a lawn is irrigated, the water soaks into the top layer of soil, and then drains through into the subsoil. The water carries vitamins and minerals as it drains, and deposits them deeper in the soil profile.

A lawn with a shallow root system will only have access to the water, vitamins, and minerals present in the first few inches of soil. Frequent watering will leach them through to lower layers of soil where the roots are unable to access them.

Shallow roots then become highly dependent on the moisture content in the first few inches of soil, which evaporates very quickly compared to deeper layers. Due to a lack of adequate available nutrition, and a constant cycle of extremes in moisture, the lawn becomes stressed.

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There are plenty of resources for the roots in the soil, but the plants are too stressed to grow towards them. A continual cycle of frequent, shallow watering coupled with incorrect mower height will keep the roots from forming a healthy root system.

Once the lawn is in this state, intervention becomes more frequent and costly to maintain the appearance of healthy-looking grass. Fertilizers will help in short bursts, and irrigation must happen more frequently to prevent wilting. Both practices reduce the health of the lawn even further.

Healthy maintenance practices are key to healthy root systems, but some grasses are prone to shallow roots in spite of proper lawn care. This is why choosing a resilient, deep-rooted turfgrass is the first step in stress-free lawn maintenance.

Deep-rooting grasses are less prone to drought and are able to feed from deep nutrients in the soil.

Turf Grasses With The Deepest Roots

Grass is a large category, comprising thousands of different plants across the globe. However, most homeowners are not considering planting sorghum or corn for a lawn, so we’re only going to focus on the most common turfgrass species.

Turfgrasses are divided into two categories: warm season and cool season.

Not surprisingly, warm-season grasses grow best in the South, while cool-season grasses grow best in the North. The only other major distinction is that warm-season grasses break dormancy late and grow more during the summer, whereas cool-season grasses break dormancy early, and grow more during the spring and fall.

Warm Season

Warm-season grasses tend to be more drought tolerant than cool-season grasses because they grow more during the heat of summer. Drought tolerance generally requires deep roots that can access water, so it is more common for warm-season grasses to have the potential for extensive root systems.

  • Bermudagrass. According to a recent study, bermudagrass has the deepest root system potential of all common turfgrasses. (source) Roots can grow up to 8’ below the surface, although the majority of the root system remains in the top 12”. Bermudagrass is a low-growing, spreading grass that thrives in hot summers and mild winters.

Bermudagrass requires consistent mowing in order to develop deep root systems. It is not shade tolerant, and is best suited for the Southeast part of the country and parts of California.

  • ZoysiaZoysia root systems are significantly shorter than bermudagrass; reaching only 2’ in depth. However, it has a dense, thick root system for the full 2’, meaning it is much more efficient at absorbing water and nutrients in the top layer of soil.

Zoysia is easy to maintain, but it can take 3-5 years to establish a thick lawn. Zoysia can tolerate cooler weather than bermudagrass and some light shade.

Purchase from a reputable grower where they are guaranteed to grow or replaced free (link to Zoysia Farms).

Cool Season

Cool-season grasses break dormancy early and are green long before warm-season grasses. They also have a deeper green color that many associate with a lush, healthy lawn. These grasses are mowed higher than warm-season grasses, but it can take longer to fill in and create a dense, green carpet.

  • Tall fescue. According to a recent study, tall fescue has the deepest root system potential of all common cool-season turfgrasses. (source) Roots can grow 2’-3’ deep, which makes it the most drought-tolerant cool-season turfgrass. It also performs well in the transition zone between cool and warm climates.

Tall fescue tolerates shade well but does not tolerate heavy traffic. Fescue is a bunch-forming grass, meaning it does not spread aggressively and has a difficult time filling in bare patches.

  • Perennial ryegrass. This grass can grow roots over 2’ deep, which is among the deepest roots for cool-season turfgrasses. However, the roots of perennial ryegrass behave as an annual, and they die back each spring. (source) This leaves the turf vulnerable for a short period of time as it has to regrow its entire root system.

Perennial ryegrass germinates quickly but does not fill in well. It is a bunch-forming grass and does not repair bare patches easily.

There are some grasses, like centipede grass, that have extensive root systems but very narrow growth climates. If you are researching to establish a new lawn, look up the grasses that perform well in your area.

How To Encourage Deep Root Systems In Your Lawn

Deep roots are a byproduct of calculated stressors that you place on your lawn.

Mowing creates stress by removing growth, which causes the grass to respond by reinforcing itself against a perceived threat. The roots will grow deeper in order to sustain more leaf growth, and then the lawn responds by growing taller. This process prepares the turf against another “attack” on its well-being.

Consistent mowing is observably the best way to create dense, deep root systems. All turfgrasses have deeper root systems when they are mowed regularly.

Warm-season grasses tend to grow outward, not upward, and therefore require shorter mowing heights. Bermudagrass and zoysia should be cut between 1”-1 ½”, although it is far more important to follow the 1/3 rule with mowing:

Always remove 1/3 of lawn growth, but never more.

Cool-season grasses grow upward as opposed to outward, which makes them difficult to establish as a thick carpet. However, they grow much taller, and this can make them look fuller. Most cool-season grasses should be mowed 2 ½”- 3 ½”, although the 1/3 rule still takes priority.

Deep, infrequent irrigation creates stress by allowing the roots to dry out, which causes the grass to respond by growing down towards available water. However, growth requires energy, and energy requires water, so it’s important to keep your lawn hydrated enough to sustain deep root growth.

Use the 1-2-3-2-1 method to create and sustain deep root systems. (source)

  • Water once per week in the spring
  • Water twice per week in early summer
  • Water three times per week in mid to late summer
  • Water twice per week in early fall
  • Water once per week in late fall

Set your sprinklers to finish watering as the sun comes up in order to prevent mold growth. The amount of time your sprinklers run will vary for each system, but aim to water 1”-1 ½” each time.

Do not water the day of or the day after you plan to mow.

What Causes Shallow Root Growth?

Aside from incorrect irrigation and mowing practices, there are other factors that can contribute to shallow root growth in turf grasses.

Compacted soil is the most common cause of unhealthy lawns because it creates a solid, impenetrable layer called a hardpan. Without comprehensive, long-term intervention, lawns grown on compacted soil are almost continually stressed.

Clay soil is almost always compacted, due to its fine particles. Clay also holds on to water and prevents proper drainage, so roots aren’t pushed to grow deep in search of moisture.

I’ve heard many homeowners who were considering adding sand to a clay lawn to increase drainage.

Here is the formula for concrete:

Water + Sand + Clay = Concrete

Needless to say, sand is not the answer to compacted, clay soil.

Adjust your irrigation and mowing practices to encourage deep root growth, and begin aerating and topdressing with compost in the spring and fall. This will take time, but after a few years, the roots will be able to break up the hardpan as soil conditions improve.

One other possible reason your lawn has shallow roots is simply due to shallow-rooted grass. Kentucky bluegrass and bentgrass are among the turfgrasses with the weakest root systems. While improving soil conditions may help some, these grasses will never establish a deep, vibrant root system.

Consider a root growth stimulator like RGS from Yard Mastery (link to their website). This solution is a special blend of sea kelp hormones that encourage deep root growth and help to build drought tolerance.

Symptoms Of Unhealthy Root Systems

Almost all lawn issues start with unhealthy roots. Stressed roots cause stressed plants, which are then more vulnerable to pests and diseases.

  • Wilting. If you walk through your lawn and can see your footprints, your lawn is suffering from some water stress. This is not an issue as long as you water thoroughly the next morning. However, allowing the lawn to stay wilted for multiple days can cause roots to die from lack of water.

Wilting can also be the result of overwatering. If your lawn is wilted and soggy, this is a more serious problem. Roots can handle lack of moisture far better than too much moisture. Allow the soil to dry out as much as possible before returning to a 1-2-3-2-1 irrigation schedule. If overwatering is the result of heavy rainfall, consider improving your lawn’s drainage with aeration and compost to prevent oversaturation in the future.

  • Yellow or crispy brown leaves. This can be the result of severe dry conditions, but if you’ve recently fertilized, then your lawn is suffering from fertilizer burn. Too much nitrogen can cause unsustainable growth, followed by leaf scorch and root death.

Water heavily to leach excess fertilizer out of the soil, and trade fertilizing for a topdressing of compost, which will yield a long-term healthier lawn.

  • Dead, irregular brown patches. The most common cause of sporadic dead patches of turf is grubs. In the larva stage, grubs feast on grass roots, and cause severe stress. Dig up a patch to verify a grub infestation, and treat with a pesticide.

Warm-season grasses can recuperate from dead patches faster than cool-season grasses due to a spreading growth habit. If you have had a severe grub infestation, you may need to overseed a cool-season grass to help your lawn recover.

  • Weed infestations. If weeds are thriving and your lawn is suffering, this is a surefire sign that your soil is in trouble and your lawn’s roots are stressed. Weeds naturally thrive in poor soil conditions, so prolific weed growth is a signal to do some soil testing.

Check for compaction by pushing a screwdriver into the soil, or try to dig up a clump of grass. If this is incredibly difficult, your soil is compacted. Compacted soil always has nutrient imbalances, so solving a compaction issue should help resolve nutrition toxicities and deficiencies.

Aerate your lawn in the spring and fall, and add a ½” topdressing of compost. Spraying herbicides will only help temporarily, but keeping weeds mowed down before they can go to seed will prevent rapid reproduction. Over time, improved soil conditions and healthy maintenance practices will help your lawn choke out weeds and form a thick, healthy carpet.

Maintaining a healthy lawn is all about long-term maintenance practices. Improving the soil will allow the roots to support vigorous, healthy growth that resists disease and prevents weeds from taking over.

Grassroots live in the top few feet of soil, which makes it easy to make small adjustments that have a big impact. A maintenance schedule that focuses on root health gives your lawn the best possible conditions for healthy growth.

For advice on growing healthy lawns in difficult soil, visit our other lawn maintenance articles.

Are there any alternatives to turf grasses for a lawn?

Yes, but you may be limited by local regulations. Creeping thyme is a popular lawn alternative, but some cities and HOAs have policies against growing food in a lawn area. In areas with very little rainfall, you can opt for a landscape that covers your entire lawn in native plants, as opposed to trying to establish a lawn.

What if local laws prevent watering my lawn during the summer?

If you live in an area with water restrictions, you are also likely to have a warm-season grass in your lawn. Warm-season grasses will go dormant during periods of low moisture, which helps them survive drought conditions. While your lawn may turn an ugly brown, most warm-season grasses will survive a summer without water.

Recommended Reading: Growing Tall Fescue In Difficult Soil: Renee’s Success Story