Tree roots & the space they require prior to planting.

Ensuring adequate root space helps prevent issues like root girdling and competition for nutrients, fostering long-term tree health and vigor.

Brian Dean, an ISA Certified Arborist at Gail Willey Landscaping explains how landscape designers, architects and contractors need to be proactive regarding the needs of tree roots and the space they require prior to design and planting.

Tree Roots and Soil Volume 

Quick Facts

  • Infrastructure damage caused by tree roots costs millions of dollars per year to repair.
  • Without sufficient soil space for roots to grow, trees will be stunted, decline, die and/or eventually cause damage to hardscaping.
  • Landscape designers, architects and contractors need to be proactive to provide enough soil volume for mature tree growth and development.


Tree roots have estimated to cost $70.7 million annually in California to repair infrastructure damage (McPherson 2000). This does not include lawsuits involving injury or contractor defect. The average life span of a street tree growing in New York City is estimated at 3 to 15 years (Bassuk and Trowbridge).  Street trees are exposed to increased air temperatures (+20 degrees Fahrenheit) and 30% less humidity than a comparable measurement taken in a sheltered park site (Cornell University).  This causes street trees to transpire about 1.5 to 2 times as much as a forest tree (Kopinga) therefore requiring more water to survive.

Trees planted in narrow strips, small planters or “tree coffins” are an all too familiar problem for arborists and landscapers. When too little space is allocated for root systems to develop naturally, damage to surrounding hardscaping can be expected. The limited root growth also correlates to canopy growth and therefore tree health.  It can be a serious problem when trees with shallow/invasive roots are planted in these spaces. Small planting areas with compacted soil limit water and oxygen and therefore inhibit root growth.  These small open beds concentrate salt, oil and other contaminates that eventually drain into them creating a toxic environment for roots. A properly selected tree for the location will save money and labor for years to come.

Root Growth of Trees

Studies show that tree roots grow within the top 18” of soil and are capable of growing two to ten times the area beneath the canopy (Matheny and Clark 1998) and can spread more than twice the width of the canopy (Casey Trees 2008) or one and a half times the height of the tree out radial from the trunk. A trees’ ability to develop a healthy root system is dependent on soil volume. Without sufficient space for root growth trees will lack vigor, exhibit stunted growth, become susceptible to insects, disease, and drought and therefore short lived. In the absence of adequate soil space, roots will exploit available air pockets within the soil.  Roots grow where there is adequate water and oxygen.  If a tree is confined to a finite space or soil volume it is expected that the canopy spread will only grow proportionately as the roots are allowed. The tree will stop growing, decline and/or eventually die. While the tree is alive the roots will exploit pore space and possibly cause damage to surrounding infrastructure. According to McPherson and Peper “Tree roots are opportunists, utilizing structural faults in infrastructure to capture essential resources”. Kopinga states “Even small diameter roots are able to facilitate pavement damage”.

Soil characteristics such as texture, moisture content, structure and percent organic matter also play a role in how and where roots will grow.

A good source to find trees with high potential for root damage is the “Urban Forest ecosystems Institute” (UFEI) web site. The “SelecTree” guide located at the UFEI web site rates trees that are high, moderate and low in root damage potential. Below are just a few trees listed as high to moderate damage potential that grow in northern and southern Nevada.

Soil Volume Recommendations

There are many sources for soil volume recommendations and formulas in the literature that produce varied results. Some formulas use “crown projection” or square foot of canopy area projected on the ground. Others use measurements of canopy volume or the diameter of the trunk to establish soil volume. All formulas have merit however the direct relationship of canopy volume, trunk diameter or crown projection to root volume can be argued.

A commonly used formula is providing 2 cubic feet for every square foot of mature canopy or “crown projection” of a tree (Lindsey and Bassuk 1991). For example; a mature Silver Maple will spread to a width of greater than 60 feet.  Sixty feet x sixty feet = 3,600 square feet x

.7854 = 2,827 square feet x 2 cubic feet = 5,654 cubic feet.  This formula does not work if the tree has a columnar growth habit such as Lombardy Poplar or Italian Cypress. Another formula by Perry (1982) uses the diameter of the trunk to estimate soil volume. This calculation states that for every 1” of trunk caliper measured at 4.5 feet above grade or diameter at breast height (DBH) needs 27 ft3 of soil volume.

James Urban (2008) uses a combination of projected canopy and DBH based on the potential ultimate size of a tree (see table 1).

Table 1. Tree size to soil volume relationships

(Urban 2008).

Ultimate Tree Size

Example: A 16 inch diameter tree requires 1000 cu ft of soil.

 It should be noted that it is assumed drainage is adequate at the bottom of the soil column.

Root Barriers

Installation of root barriers has often been used as a solution to prevent infrastructure damage. With over 25 years of research their effectiveness has shown that the roots eventually grow out the bottom of the barriers and return in reduced numbers and size to the surface where they naturally would grow.  Harris, Clark and Matheny (2004) note that “root-control devises appear to be least effective where most needed, that is, where poor soil aeration or compaction encourages shallow rooting”.  Other observations indicate structural stability may also be compromised especially in trees with dense canopies (Pittenger 2001). However research by Smiley, Key and Greico (2000) growing Green ash showed more force was used to pull over trees in barriers as opposed to no barriers.


Landscape designers, architects and contractors need to be proactive regarding the needs of tree roots and the space they require prior to design and planting. The consequences will mean increased maintenance costs, create infrastructure damage, poor tree health, reduce the aesthetics of a landscape and possible liability.

Written by Brian S. Dean  Copyright 2016

Looking to clean up and remove yard waste? Check out our Maintenance page for more info HERE.

Dogs and your lawn can coexist!

With proper care and maintenance, dogs and your lawn can coexist harmoniously, keeping both your pets happy and your grass healthy.

Here in the Reno Nevada area many homes have small lawns. Small lawns are a way of conserving water and keeping maintenance to a minimum. Natural turf not only to adds a little green in a sea of beige, brown and tan, but  gives the home owner a place to throw a ball and play with the pets. Lawns are technically speaking a large colony of plants. Most of us treat this plant colony like carpet … walking all over it even jumping up and down on it!  …. don’t try this with your shrubs or flowers! These tiny plants are the most durable little guys out there!  Despite all of this abuse your lawn has one arch rival one it doesn’t stand a chance at without a little help…. your dog.  Look at it from your lawns perspective…. you walk all over me, stomp on me, cut me down, and now your going to …. well pee on me!  … peace out brother… I’m done!

“Look at it from your lawns perspective…. you walk all over me, stomp on me, cut me down, and now your going to …. well pee on me!  … peace out brother… I’m done!”

All hope is not lost. With just a little tender loving care and consistency your lawn and your dog can co-exist.  Here are a few guidelines to keeping a green lawn, and taking care of those little dead spots in the lawn.

1. Keep your turf strong and healthy with a regular fertilization program.  The number 1 thing you can do for a great looking lawn is apply fertilizer and weed control at the PROPER TIMES.   Timing is everything when it comes to lawns,  and if you do the numbers you’ll quickly realize for the price of a decent bag of fertilizer you can have a pro do it for you!  Your pro will apply the fertilizer / weed control  at 5-6 intervals throughout the growing season and at exactly the right time.

2. Water . Lawns like water … way more than your trees and shrubs. … after all it’s an entire colony of plants! Water will also help with Rovers need to pee on the grass.  This said too much water is a bad thing… and will make your grass colony little water addicts and rinse out the nutrients your pro so carefully put down… not to mention leave you with a soggy lawn… soggy = bad

3. Once your lawn is healthy and a solid weed free green, it’s time to tackle those pesky doggy spots.  The first item you will want to do is halt weed control. Let your pro know you’ll be seeding and to halt all weed control for 1 month. Weed control often includes pre emergent. Pre emergent does not allow seeds to germinate… even the good grass seed.  Once your month is up scarcity the doggy patches with a rake or hand tool loosening the soil… leave some of the dead grass as it’s a good mulch for the seed you’ll throw down.  Simply sprinkle some bluegrass seed ( or a seed that matches your lawn grass)  in the dog spot areas , then make sure you go one more month with no weed control application ( fertilizer is fine).  Patience is key. Grass doesn’t germinate and grow over night so it takes some time .  Since your dog won’t stop peeing you won’t stop doing seeding repair, but if you watch your lawn and keep it healthy you’ll only develop a few patches to repair over the course of the season and likely will only need to have 1-2 patch  lawn exercises a season.

4. Pick up after your dog. … everyone’s favorite job right? Once a day is ideal never let it go more than 1 week as it will likely kill the lawn in that spot. In cold climates it’s  even more important to pick up daily in the winter. For the royalty out there I’ve noticed doggy do pick up services, a quick google search will let you know who’s closest.

In summary:

1. Regular fertilization 5-6 times a year
2. Water
3. Scarecify and seed spots while halting any weed control
4. Pick up dog debris often

– G. Berg

Looking to clean up and remove yard waste? Check out our Maintenance page for more info HERE.

Pines shed their needles the same as a leaf!

Just like deciduous trees lose their leaves, pines regularly shed their needles to make way for new growth.

Interior needles turn brown and fall off creating a natural mulch for the tree..

If your needles are turning brown from the tips that indicates a potential problem with the tree.

As we move into fall and irrigation systems are turned off for the winter,  it’s important to water not only your evergreens but all of your plants.

– G. Berg

Looking to clean up and remove yard waste to assist in fire safety? Check out our Maintenance page for more info HERE.

How to Winterize and Restart an Irrigation System

This post is based on our original pdf about winterizing irrigation systems.

Winter Shutdown Procedure

  1. Close the main supply/shutoff valve (marked in blue.)

    looking down the stand pipe at the irrigation main valve

  2. Open all 1/4″ ball valves on the backflow preventer.

    backflow preventer with the correct "open " or "on" postition

  3. Turn ball valves on the backflow preventer to a 45 degree (or less) angle.

    backflow preventer at 45 degress

  4. Open all drains in the main line and in the valves boxes (marked in green).

    drain covers

  5. Open all bleed screws on the valves or turn all solenoids to the “ON” position.

    Bleed screws on valves

  6. Turn clock to the “off” position.

    Clock in off position

  7. Cover the backflow preventer with a backflow blanket.

  8. Check the hose bib to be sure you did not turn off the house water supply!
  9. Your house main is marked in red.

When should I water my landscape in the winter?

You should consider watering your landscape if:

  • The temps have been mild with no significant rain or snow in the forecast.
  • You have not received rain or at least 4″ of snow in the last two weeks.

For shrubs and trees:

Wait for days with average temperatures of 40ºF. Water deeply all around the root balls. Planted trees will take at least three gallons, while shrubs only need one gallon.

For lawns:

Do not water frozen soil. You can water your lawn by turning on your irrigation system, letting it cycle, turning it back off, leaving enough time for it to drain before the temps drop below freezing. Alternatively, you can hook up your hose and hand water your lawn. Remember to disconnect your hose, drain it, and store it in the shed or garage.


Fertilizing or feeding your landscape plants should wait until March or early April. Consult with your local nursery for the best nutrient mix.