Growing Trees on Your Lawn
Trees are planted on lawns so often that you probably take their
peaceful coexistence for granted. They may seem like natural companions,
but they are not. Each weakens the other so that both of their immune
systems are compromised. Fortunately, you can help the immune systems
of both by observing and mimicking nature.
The best kind of yard is an organic yard. Pesticides, herbicides,
and chemical fertilizers are harmful to the environment and your yard.
They destroy beneficial microbes that live in the soil. These microbes
are essential to the immune systems of your lawn, trees, and other
growing things. Destructive diseases and other pests attack weak plants
with compromised immune systems and are a symptom and contributor
to a plant's decline, not the cause.
The cause is usually a whole range of problems, such as the use of
chemical fertilizers and pesticides, the wrong soil pH, or plants
that aren't naturally compatible.
Understanding Plant Relationships
Walk through a natural forest and observe how the trees grow and
what grows under the trees. There is very little grass because there
isn't enough light. The lower branches of the trees are missing because
there isn't light for them either. Both grass and trees need light
because they both use the sun to turn water and minerals into carbohydrates
and other necessities. This is done through the process of photosynthesis,
which we will review later.
In a forest, the trunks and branches you see are part of a vast structural
system that also acts as a food storage site. Photosynthesis takes
place in the leaves at the top of the trees. When leaves die, they
fall to the ground and are naturally composted into humus. This provides
a rich environment for tree roots. Most tree roots are near the surface
because that is where the humus is located. It is also the home of
beneficial fungi, bacteria, nematodes, and other micro life forms
that help trees and other plants absorb the minerals they need.
The only places where you will see grass are the areas where there
is enough light. Within a forest, there is often grass near creeks,
rivers, and in natural clearings. Even grass needs humus to be healthy.
Some areas of the world have vast natural grasslands, such as the
Great Plains of the Midwest. When grass dies, it is eventually turned
into humus by soil micro and macro organisms. The humus feeds new
On the other hand, many of the grasslands that you look at and assume
are natural, aren't natural at all. In many parts of the world, the
valleys have been deforested and crops planted in their places. Steeper
hills around valleys have been deforested as well, so that cattle
or sheep can graze.
As an example, in the Silicon and Sacramento valleys of California,
vast tracts of oak forests were removed from the valley floors and
replaced by crops and orchards. Many of the hills around the valleys
were also deforested so that cattle could graze. When cattle or sheep
graze in an area, they eat the seeds and nuts so that new trees don't
grow. Many of the hills around the valleys aren't used for grazing
anymore, but the trees haven't been able to grown back.
It is important to understand that your yard is a whole growing area
and that your plants will grow best when they are compatible with
the soil, climate, and each other. By understanding more about soil,
pH, photosynthesis, and a few other things, you will be able to grow
healthy trees in on a healthy lawn. Compost and humus are often used
interchangeably when referring to the end product of composting.
If you live in a subdivision home like many of us, all of the topsoil
and natural humus was hauled away during construction. What does that
mean for your garden? It means that you are left with dead dirt-you
must start from scratch to breathe life into it.
There are many variations of soil composition, but the three basic
types are sand, clay, and silt.
1. Sandy soil is easy to work with and drains quickly, but it can
dry out too quickly for many plants.
2. Clay is very heavy and hard to work with. When it is dry, it is
very hard and when it is wet, it is very sticky. Drainage is poor.
3. Silt drains reasonably well and is workable when wet, but very
hard when dry.
Most soil is a composite and has varying amounts of organic material.
It may also have varying amounts of rocks. Regardless of which one
of these soils you have, or what composite you have, the secret to
helping your garden is the magic of composting. Composting turns garden
waste into humus. It mimics nature.
pH is a measure of acidity vs. alkalinity in a substance. pH is measured
by the number of hydrogen atoms in a solution and uses a scale of
1 to 14. 1 is extremely acidic and 14 is extremely alkaline (or basic).
7 is neutral.
The formula is: pH = -log10 [H+]
Since pH is logarithmic, 6 is 10 times more acidic than 7 and 5 is
100 times more acidic than 7. It follows that 8 is 10 times more alkaline
than 7 and 9 is 100 times more alkaline than 7.
This is important to understand because most plants grow best in
a slightly acid to neutral soil (pH of 6 to 7). Actually a pH of 6.5
is the point where minerals become most available to plants. As an
example, nitrogen, phosphorous, potassium (NPK), and trace elements
are most readably accessible at a 6.5 pH. A 6.5 pH is only slightly
acidic. If your lawn or trees look like they are missing an element
such as iron, the real problem may be that the pH is too far out of
the 6.5 range for the grass or trees to absorb it. Test your soil
with an electronic soil
and pH tester to find out how your soil rates.
Photosynthesis and Plant Growth
Photosynthesis is a complex mechanism that uses the sun's energy
and water to convert carbon dioxide into carbohydrates and simple
sugars. The byproduct of photosynthesis is oxygen. Water (H2O) plus
carbon dioxide (CO2), becomes carbohydrate or glucose (the exact chemical
composition depends on the plant) plus oxygen (O). Thus, the plant
has food and we have oxygen plus food (plants are food for us).
The secret of photosynthesis is chlorophyll, which is stored in chloroplasts
in leaves. During photosynthesis, the sun's rays are absorbed by chlorophyll
and used to create simple sugars and carbohydrates. The color of the
leaves, usually green, is the only part of the color spectrum that
isn't absorbed. Instead, we see it reflected as the color of the leaf.
Before photosynthesis can take place, the roots must pull water and
minerals up from the soil to the leaves. This pumping process is called
transpiration. Chlorophyll in leaves absorbs the sun's energy. Pores
on the underside of leaves (called stomata) absorb carbon dioxide
while allowing oxygen and water vapor to exit. Photosynthesis uses
the water and minerals pulled up by transpiration, plus carbon dioxide
from the air, to create carbohydrates, simple sugars, and other plant
Healthy grass, trees, and other plants have healthy root systems.
Healthy root systems are the most interesting and misunderstood part
of plant life. Roots systems rely on fungal root systems, called mycorrhizae,
that attach themselves to the root hairs and significantly increase
the absorption area of a root system. This fungal root system uses
a small amount of the plant's energy, but absorbs microelements that
would otherwise be unavailable to the plant.
The rhizosphere is the moist area that extends approximately one
millimeter around roots, root hairs, and mycorrhizae. It is teeming
with microscopic life forms that are both beneficial and pathogenic.
As long as the plant is healthy and the correct balance of air, water,
pH, and other factors is maintained, the plant's natural defenses
keep out pathogens. But once the natural balance is disturbed, the
root system is disrupted and pathogens can get a foothold.
As an example, oak root fungus (Armillaria) is a common soil fungi
found in most soils, but remains dormant until conditions are right,
and the tree begins to weaken. If you use a fungicide to kill oak
root fungus, you will totally disrupt the natural soil environment
and the tree will be attacked by other pathogens. The best way to
keep oak root fungus away is to ensure lots of beneficial life forms
in the soil.
The root system is just as important as photosynthesis for healthy
plants. Unfortunately, the typical way to deal with the dead dirt
of a new subdivision house is to cover the dead dirt with several
inches of topsoil, install a sprinkler system, dig holes for trees
and shrubs, and lay down sod. Planting mix is used in the holes where
the trees and shrubs are to be planted.
Once everything is set up, you begin watering, adding chemical fertilizer
at the proper intervals, and of course using the proper herbicides
and pesticides. This system does not work with nature, but against
nature. The topsoil is devoid of humus, the leaves and cut grass are
raked up, and the chemicals kill the micro life forms that could have
made humus. High nitrogen fertilizers also acidify the soil so that
it gradually becomes too acidic for most of your plants, forcing you
to add lime. In addition, chemical fertilizer creates shallow roots
that make grass and trees susceptible to drought. Fortunately, you
can bring health back to your yard.
If you want a yard that is healthy, alive, vibrant, and free of chemicals,
learn about composting. The end result of compost is humus, which
is nature's own fertilizer. Compost adds structure to soil and acts
as a natural buffer, which allows plants to absorb minerals in a much
wider pH range. The micro life forms in compost also help to neutralize
pH extremes. With the help of compost and proper watering, the grass,
trees, and other plants in your yard will grow deep roots and have
very little difficulty with the pests that menace other yards. To
learn more about composting, see the following website Compost
Improving Your Lawn and Its Trees
Although lawns and trees aren't naturally good companions, there are
things you can do to help their association, even if you have an old
lawn and old trees.
One thing that is often done to help lawns and trees coexist is to
use a seed mix that contains both sun loving and shade tolerant grass.
A typical mix is Kentucky bluegrass, tall fescue, and annual ryegrass.
This can be helpful because all three seeds can grow in the 6 to 7
pH range and the shade tolerant grass can eke out an existence under
a large tree.
Unfortunately, another method is often used. Large trees are severely
pruned. Many of the lower branches are removed and the tree is thinned.
This dramatically reduces the glucose storage area, which the tree
needs for new leaves and root growth. It often leads to a gradual
decline and death of the tree. Young trees can handle a significant
amount of pruning, but old trees can tolerate only light pruning.
The preferred tree pH is often not considered when trees are selected
for lawns. As an example, European white birch trees grow on many
lawns (often in groups of three). In many areas they are thought of
as sensitive trees because they are susceptible to disease. Actually,
the problem is that lawns usually have a pH between 6 and 7, while
European white birches grow best in an acid soil with a pH of 5 to
5.5. Of course, they also prefer a cold climate.
Improving an Existing Lawn and Trees
If you have an existing lawn with trees growing on it, don't rush
into things. Dig into the lawn in an unobtrusive area to see what
is underneath the grass. Often there is a layer of topsoil over the
original graded earth and nothing else. Take a sample of the soil
from several different areas in the lawn and check the pH. This will
tell you what you have to begin with. It will also be a reference
point to give you an idea how your soil changes as you improve it.
Most gardening centers have a variety of pH testing kits.
Adding compost will help, even if your lawn is very acid or alkaline.
The buffering effect of compost is extremely good at neutralizing
pH extremes. Aerate your lawn and spread compost on top. If you haven't
started composting yet, you will have to purchase compost. You can
also use organic
fertilizer. Find out more about aerating your lawn and using compost
or organic fertilizer, at the Organic
Tips: Mature Lawn Trees
If you have an old tree on your lawn, there are important things
to understand. There are also precautions to take. Tree roots extend
far beyond the drip zone. When you aerate the lawn, be careful not
to damage major roots. Do not aerate near the trunk.
If you have an old tree with a significant surface root problem,
you may have to live with it or remove the tree and start from scratch.
Some important considerations follow:
- Digging up offending roots may severely damage the root system
and health of the tree.
- Covering the offending root area with dirt and planting new seeds
will change the oxygen level of the tree roots and probably cause
significant damage to the tree's health.
- Adding up to three inches of mulch around your trees is beneficial.
Wood chips from a tree company work well as mulch as long as they
are not fresh. Fresh chips or other mulch need nitrogen to decompose
and will rob the ground and your root system of nitrogen. The mulch
is light enough that it won't impact the soil oxygen level and the
mulch will eventually decompose into humus. The mulch should not be
too close to the trunk.
- Some trees are especially prone to surface root problems. Poplar
and willow trees are examples.
- Removing the old lawn and reseeding or resodding will severely
damage the health of trees growing on your lawn.
If you have an old lawn, and want to plant a new tree, that is fine.
Look in the next section to find out about planting trees and things
to watch for when deciding on a tree.
Tips: New Lawn and Trees
There is a lot of information available on organic gardening in books
and on the Internet. There are also contractors that specialize in
organic landscaping. Do some thorough research before you begin. A
few important things that aren't usually addressed follow:
- It is best to use plants that are native to your area, or are native
to a similar area. They will naturally tend to be healthier.
- If you look closely at trees in a nursery, you will find that the
top has been clipped off of many varieties. This is an old tradition
intended to make the tree spread out as it grows. However, every tree
has its own branching pattern and topping, even when very young, often
disrupts the branching pattern. This often leads to a dangerous tree
when mature. A prime example is the liquid amber. Liquid ambers normally
grow with a straight vertical trunk and horizontal branches. They
are very sturdy trees. However, when they are topped, they develop
two or more main trunks that are connected by a very weak crotch.
These weak trunks are very susceptible to storm damage. Try to find
a tree that hasn't been topped.
- Small trees that don't have to be staked are best because they
develop a strong trunk.
- Young trees can handle more pruning than older trees, but do not
- Make sure your lawn and trees have compatible pH's.
- When you plant a lawn tree, mulch a ten-foot area around the tree.
This will help develop a healthy root system. The tree will grow much
more quickly because it won't have to compete with grass roots. Use
a weathervane or garden
arbor at your house!
- When deciding where to plant your lawn trees, consider the location
of your utilities. If you plant a tree over a gas, water, underground
electrical, or underground cable line that has to be repaired in a
few years, you will have a big problem.
- Tree roots love to grow under sidewalks, patios, and driveways.
There is usually a layer of sand and or gravel right under the cement.
This traps moisture and air, and the roots have a field day. The result
is lifted cement. If it is a sidewalk, the roots usually grow right
under it and into the lawn on the other side. On the other hand, they
seldom go under a foundation because it is too deep to contain sufficient
oxygen for root growth. Do not plant trees close to these areas. You
can help to reduce root damage by using a product referred to as 'root
block.' It is a roll of plastic that you insert vertically into a
trench next to the cement. The roots usually won't grow under root
- Remember that a little sapling grows into a mighty tree. Make sure
there is enough room before you plant. Look up. Are there obstacles
- Are you using a reel mower
to mow your yard? If you have a small to medium sized lawn, reel
mowers make working outside a lot more pleasant.
- Check the variety of tree you plan to use to make sure that it
is compatible with lawns. What pH does the tree prefer? How much water
does it need? Before you choose a tree, look for it in parks and yards
of other homes to make sure it doesn't have surface root problems.
For excellent instructions on how to plant your trees, see Tree Planting
Fact Sheets. This website also has general information on trees and
a link to Dr. Shigo's books. Dr. Shigo is the father of modern aboricultural
science. He has debunked old myths and improved our knowledge of trees
and their interaction with the environment.
Now you have a basic understanding of why organic lawn, trees, and
yards are important. You also know that you can change your yard from
a chemical cocktail to an organic Eden. It's time to begin.