In the Morvan in France, near its northwest border, is a small forest that I steward, love and protect, part of the family estate, 14047 trees, each listed, over 2000 of which I have planted myself. Looking after trees and growing up with a forest as part of my family, I have learned a few things about forestry which I now share for those thinking to grow trees.
We begin with the basic:
that in the first five years of their life trees generate a considerable amount of Oxygen, essential for our atmosphere, each new tree generates enough O2 for 2.4 people every year for five years. It has long been known that one of the easiest ways to combat atmospheric change due to air pollutants is to plant a young tree every year (I plant 600 every year).
Some trees then give rise to more O2 than others, some need more space than others, but every type of tree brings benefits and the ideal forest is a balanced arboreal ecosystem.
Tree growing is then about knowing what prevents tree growth, what kills or damages trees, what stunts their growth and thus creating the environment and circumstances where trees can thrive.
Trees need space, good and well-drained soil, some rainfall, to be free from disease and to have access to sunlight. They tell you when they are healthy and happy in many ways, through leaves, or their welcome as we climb them, through their bark, the types of fungi around them, through regular conversation, and also tell us when they are unhappy. Talk to them, it really helps.
Trees develop vigor as they get older, they are resilient to disease and environmental change BUT when attacked from different directions they eventually use up their quota of vigor and the begin to die through starvation. The first lesson therefore of growing trees is to understand what kills them and then protect our trees from this.
How do trees die?
There are 5 factors to which a tree eventually succumbs: death from its environment, death from harmful insects and diseases, death from a catastrophic event, death from age-related collapse (including its starvation) and death from being harvested. In most cases, death is the result of several, if not all of these conditions taking place simultaneously.
Environment
A tree is in constant balance between its vigor, its food and the stressors in its environment. Minimizing stress on a tree prolongs its natural life
A disease or parasite (see below) that appears to be killing a tree may in effect be doing so because the tree's own defense mechanisms (its vigor) is taken up defending it against environmental stresses. Part of helping a tree survive a disease or parasite includes improving the tree's environment.
The environment can be monitored and made more healthy. Creating well-drained soil, reducing salt or balancing Ph in the soil, ensuring there is a clean, flowing water supply for the roots all prolong a tree's life (so map the water table and water cycle). Also aid the tree by removing sources of air, water and ground pollution (again measure each regularly), or protect it from the extremes of sun, cold or high winds, often resolved by terrain but also the forest itself will create shelter - important is to note where the forest offers natural shelter as this is the best location for new planting.
Over-density of planting and failure of natural or excessive man-made planting for harvesting sees trees become more prone to disease as they compete over nutrients, sun, air, and water. Then each species of tree has specific requirements that can include competing over pollinates eg planting pear trees near apple trees or needing to cross-pollinate male to female
The dangers to trees today (with articles on increasing tree death in America and Canada for example) come from a combination of undergrowth clearance, soil, water, and air pollution, excess harvesting, overdensity of planting, excessive use of fertilizers, whilst the loss of trees (and the shade they provide as well as the cooling impact their roots have on the core ground temperature 4m down) is increasing the temperature of the ground and thus impacting on climate as well as seeing O2 levels in the atmosphere reduce.
Density
Most recent research has been into those orchards and tree species where greater density of planting can be achieved. None of this research looks at the longitudinal impact on soil quality rather they look at the opportunity to increase fruit harvests. If proposing to move above the 1200-1400 trees per hectare of a mixed-species forest then monitor the impact on the humidity, PH and nutrient base of your soil. Trees have survived for billions of years thus far through the careful harvesting of their own soil and begin to starve if planted in too great a density for soil, air and water cycles to serve.
The density then reduces if Dbh is below average (Dbh is the measure of the bark circumference of the trunk). Each species has a young, middle-aged and veteran or ancient tree range for Dbh but ideal density is calculated based on veteran Dbh. If you plant more young saplings because they begin with a small circumference of trunk you must plan to harvest some of them to permit others to then grow.
If we take the oak we see how measuring Dbh (girth) and density change with the age of our trees. This shows for example not only the degree of natural harvesting but also if we seek ancient healthy trees the importance of our own harvesting program.
The girth of Oak trees
The girth of tree Est age in years Density per hectare
1ft to 3ft 1 - 5 1400-1800
3ft to 6ft 6 - 74 800-1200
6ft 1-2ins 75 800-1000
6ft 6-7ins 80 800-1000
8ft 100 300-400
10ft 135 250-300
12ft 180 200-250
14ft 230 150-200
16ft 6ins 290 120-150
18ft 6ins 350 100-120
20ft 6ins 430 100-120
22ft 6ins 510 80-100
24ft 6ins 600 80-100
26ft 6ins 700 80-100
28ft 6ins 800 70-80
31ft 920 60-70
33ft 1040 50-60
Soil PH
Soil PH should ideally be around the 6.0-6.5 mark and this is impacted by the amounts of nitrogen, phosphoresce, potassium, sulphur, calcium, magnesium, iron, manganese, boron, copper, zinc, aluminium and molybdenum found in our soil (there are also ideal levels of each found in our blood and the two broadly correspond meaning when we get our soil PH wrong we also see this imbalance come into our food and into our blood supply causing numerous diseases from heart, liver, pancreas, endocrine and kidney disease to cancer.
Different trees require different ranges from this and so in the ideal forest one can create a mix of soil types, done through undergrowth planting but also we understand the natural PH of our soil and work with it in our planting:
Trees and Shrubs Soil PH
Apple 5.0-6.5
Ash 6.0-7.5
Azalea 4.5-6.0
Lime or Linden 6.0-7.5
Linea 6.0-7.5
Beech and Copperbeech 5.0-6.5
Birch 5.0-6.5
Blackberry 5.0-6.0
Blueberry 4.0-6.0
Boxwood 6.0-7.5
Cherry, sour 6.0-7.0
Chestnut 5.0-6.5
Crab apple 6.0-7.5
Cyprus 6.0-7.0
Dogwood 5.0-7.0
Elder or box 6.0-8.0
Elm 5.0-6.5
Fir, balsam 5.0-6.0
Fir, Douglas 6.0-7.0
Hemlock 5.0-6.0
Hydrangea, blue 4.0-5.0
Hydrangea, pink 6.0-7.0
Juniper 5.0-6.0
Laurel 4.5-6.0
Lemon 6.0-7.5
Lilac 6.0-7.5
Maple 6.0-7.5
Oak 5.0-6.5
Orange 6.0-7.5
Peach 6.0-7.0
Pear 6.0-7.5
Pecan 6.4-8.0
Pine 5.0-6.0
Pine, white 4.5-6.0
Plum 6.0-8.0
Raspberry 5.5-7.0
Rhododendron 4.5-6.0
Spruce 5.0-6.0
Sycamore 5.0-6.5
Walnut 6.0-8.0
Willow 6.0-8.0
Soil moisture and root depth
This can be measured using a sensor and by routinely turning over the topsoil but the key is there is a direct correlation between the root density and soil depth that should be regularly tested [the formula is y = -17(logx) + 82.29]. Even in deep and the most fertile soils the majority of roots are in the first 3 feet, not least as soil temperature increases as we go deeper. If a tree is deep rooting then this is a sign it is under stress eg high winds lead to establishing deeper roots or dry topsoil will see deeper taproots sent out
Air Pollutants
Most pollutants weaken trees ie they reduce tree vigor and so make trees more vulnerable to parasitical or disease attack. In the air, the big risks are from ozone, sulfur dioxide, and nitrogen oxides the latter also found in "acid rain".
Elm, poplar, pine, and willow are especially vulnerable to air pollution whilst box, fir, oak, and dogwood are the most resilient. Air pollution can thus change the range of tree species in a forest (moving towards those which photosynthesize the least per hectare and thus reducing O2 released into the atmosphere).
Measuring CO2, methane, ozone, CFC, SO2, NO, HF and SF3 in our atmosphere helps identify if our trees are being stressed by pollutants or not. Different species are then more or less tolerant of air pollution as follows:
Trees and ozone sensitivity
Tolerant
Abies balsamea - Fir, balsam
Abies concolor - Fir, White - Fir, white
Acer saccharum - Maple, sugar
Betula pendula - Birch, European white
Cornus florida - Dogwood, white
Ginkgo biloba - Ginkgo
Ilex spp. - Holly
Juglans nigra - Walnut, black
Nyssa sylvatica - Gum, black
Picea abies - Spruce, Norway
Picea pungens - Spruce, blue
Pinus resinosa - Pine, red
Pseudotsuga menziesii - Fir, Douglas
Quercus robur - Oak, English
Quercus rubra - Oak, red
Taxus spp. - Yew
Thuja spp. - Arborvitae
Tilia americana - Linden or Basswood
Tilia cordata - Linden, little-leaf
Intermediate
Acer negundo - Boxelder
Cercis canadensis - Redbud, eastern
Liquidambar - Gum
Pinus echinata
Pinus sylvestris
Quercus cocceina - Oak, red
Quercus velutina - Oak, black
Syringa spp - Lilac
Ulmus parvifolia - Elm, lacebark
Sensitive
Fraxinus Americana - Ash, white
Fraxinus pennsylvanica - Ash, green
Gleditsia triacanthos - Honeylocust
Juglans regia - Walnut, English
Liriodendron tulipifera - Poplar, tulip or yellow poplar
Malus spp - Crab apple
Pinus nigra - Pine, Austrian
Pinus strobus - Pine, eastern white
Pinus taeda - Pine, loblolly
Pinus virginiana - Pine, Virginia
Platanus occidentalis - Sycamore, American
Quercus alba - Oak, white
Quercus palustris - Oak
Salix babylonica - Willow, weeping
Sorbus aucuparia - Mountain ash, European
Trees with a range of sulfur dioxide tolerance and sensitivity
Tolerant
Acer saccharinum - Maple, silver
Acer saccharum - Maple, sugar
Ginkgo biloba - Ginkgo
Juniperus spp. - Juniper
Picea pungens - Spruce, blue
Quercus palustris - Oak, pin
Quercus rubra - Oak, red
Thuja spp. - Arborvitae
Tilia cordata - Linden, little leaf
Intermediate
Acer negundo - Boxelder
Acer rubrum - Maple, red
Pinus nigra - Pine, Austrian
Populus deltoids - Cottonwood
Quercus alba - Oak, white
Sorbus aucuparia - Mountain ash, European
Syringa spp. - Lilac
Tilia americana - Linden or Basswood
Ulmus americana - Elm, American
Sensitive
Amelanchier - Serviceberry
Betula - Birch
Fraxinus pennsylvanica - Ash, green
Pinus strobus - Pine, eastern white
Populus nigra ‘Italica’ - Poplar, Lombardy
Salix nigra - Willow, black
Ulmus parvifolia - Elm, lacebark
Water pollution
Pollution in water not only harms tree growth but also allows trees to absorb dangerous chemicals from the water and pass them on to animals that rely on them for survival. Tree fruit also passes on these pollutants to humans when we consume them.
Polluted water in the ground washes the essential nutrients trees need out of the soil. Water pollution also makes the soil acidic and negatively affects the solubility of nutrient ions, such as iron, magnesium, potassium and calcium ions. As a result, water removes these nutrients more quickly from the soil and sends them into streams and lakes. Calcium and magnesium, in particular, are critical for proper tree growth. Iron helps trees to create the pigment chlorophyll, which is necessary for food formation, while potassium helps trees to use water. Without these nutrients, trees become more susceptible to drought, fungal infection, and parasites. Water pollution also leaves large amounts of aluminum in the soil, which can be harmful to trees and then to humans when it enters the food chain.
Always test water flowing across our land for total dissolved solids (TDS). Tap water for drinking usually has between 120 and 420 particles per million (ppm) of contaminants, the spring water we use in my forest sits at 22-38 ppm and 0 aluminium, chlorine, fluorine, hormones, arsenic, THMs and pesticides (but does have salt, copper, lead and nitrates at very low levels, the nitrates in the water are from fish excrement and are removed by the lettuces we grow in our hydroponics farm).
Diseases and parasites
These work in a number of ways: those diseases that are fungal based and where the fungus either takes nutrients from the tree through its resin system of trichomes or competes with the tree for nutrients in the soil. Others attack the leaves causing "blight" which reduces a tree's ability to absorb energy through photosynthesis, yet other parasites or diseases consume the bark and leaves.
A tree shows disease rapidly by leaf curl, discoloration, stunted growth, dead buds and/or dead branches and crumbling bark. Routinely talking with and climbing trees will rapidly tell you if a tree is struggling. If a disease is allowed to get too firm a grip then it is carried by the root system and by the act of harvesting to other trees and it leads to tree starvation and eventually a tree collapsing inwards. All diseases I have encountered can be resolved by helping the tree gain vigor, the exceptions are diseases introduced that are unfamiliar to a species of tree, usually introduced through the use of pesticides or introducing a species of tree or plant not familiar to the natural ecology.
The three most damaging diseases worldwide are Armillaria root rot, oak wilt, and anthracnose. They damage the trees vascular system and attack through the bark, untreated wounds, and roots. Most forests work on the basis of prevention but this weakens tree's natural vigor and ultimately makes trees susceptible to other diseases. I prefer to work on natural prevention through strengthening the vigour of trees, avoiding over density, ensuring good water flow and drainage and routine harvesting to ensure there is always a proportion of new stock. On the rare occasions, I have encountered any of these diseases then I have removed trees, roots and zoned the area then tested the soil, left fallow for two years before replanting tree species not vulnerable to these diseases.
Problem insects include pine beetles, the gypsy moth, and emerald ash borers and these will defoliate, eat through the cambial layer of the bark, allowing other diseases to then attack the vulnerable vascular layer of the tree or spread harmful fungi from one infected tree to another. Harmful insects can kill a tree rapidly and so I encourage spiders and other similar predators (I have some seriously BIG garden spiders in my forests, most then come to the house for shelter and food and to nest). Bees, lacewings, and ladybirds are also helpful for healthy tree growth.
Damage due to an event
Storm damage to trees if not treated can lead to vulnerability to disease and parasites whilst high winds, fires, flood, and landslides, all weaken the vigor of trees and can lead to their premature death. Heavy ice or long periods of extreme cold or heat, the weight of snow on treetops can also all do huge damage.
Even if a tree has been struck by lightning and caught fire still try and save it through tending its wounds, increasing nutrients in its soil, offering it water, comfort, and companionship. I once slept two nights with a tree to see it through the worst of a lightning strike. If your tree is bleeding it needs a bandage and medication just as we do. Sometimes it is necessary to then prune a damaged tree in order to give it enough chance to recover (by reducing the amount of foliage it must try to feed through its damaged vascular system). Most events leave the root ball undamaged (except for landslide or a heavy frost) and so a tree has a chance to recover with our help.
A tree can then drown if the root system is left underwater following a flood for any prolonged length of time and so any healthy forest that is exposed to flooding should develop a network of drain ways whilst be ready to divert water away from flooded areas to give your trees a chance to recover.
Aging
Trees do expire of old age - essentially they become too large for their root ball to support the foliage and/or the vascular system begins to slow down. An old tree collapses in on itself to become the nutrients for new trees. I lost one fourteen hundred-year-old walnuts in 2001 and three have since grown where it used to sit and are maturing nicely.
Harvesting
There is a natural process of harvesting trees that sees some trees die early to make space for their cousins and neighbors. Forestry then requires harvesting of trees for a number of reasons: to avoid over density, to avoid the spread of disease or a parasite, to protect water flow, and then copping as part of the wound and damage care. A high proportion of trees harvested are harvested for timber however and the demand for wood and wood pulp for paper has led to deforestation. My own forest has a target to increase the tree population by 3% per annum plus and extend the boundaries of the forest by 2% per annum. We harvest (and see die naturally) up to 17% and plant a new 20% each year. We look for 20% of our trees to be 1-5 year old at any time being the most productive of O2.
Planting trees
Most of correctly planting a tree are about preparation ie
My Planting Plan
Select tree species (avoid introducing something inappropriate for existing ecology) and check ideal soil Ph for tree
Select location (shelter, drainage, sunlight, density)
Survey environmental factors eg climate, winds, rainfall
Survey for any underground or overground utilities and wireless or TV signals
Base any planting (location, density, species) on mature tree size
Source from a safe source (disease and parasite free stock)
Test soil for moisture, PH, nutrients, and drainage
Avoid replanting where there are the remains of a tree that has died of disease or parasite until certain the entire root ball has decayed or been removed
Test water cycle and water purity
Plant during the dormant season (after leaf drop or in spring before budding)
Turn over the ground into which the tree is to be built and ensure there are enough worms in the soil (you may get transplant shock depending on how good your supplier is at protecting the root ball but good soil preparation can offset this)
Identify the trunk flare (the fat bit that should be just above the ground)
Dig a hole that is just 2-3 inches deeper than the root ball but three times the diameter of the root ball
Remove any container or netting or wire and prune off any circling roots that will prevent the root ball from expanding
Place a small line of firmly packed soil directly beneath where he tree is to go raising the tree such that the flare is just above ground level
Do not plant too deep, remembering most roots form just beneath the surface (see above) and if roots are too deep they are starved of oxygen
Straighten the tree (has to be done by eye but needs someone to hold and someone else to step back). The person gauging if the tree is upright needs to ensure their own feet are planted on the level
Fill and backfill slowly, packing and watering as you go to eliminate any air pockets
Stake the tree if there is no shelter and risk of winds or there is a risk of phototropism leading to the tree growing at an angle or being vulnerable to crosswinds. Use adjustable ties and do check them regularly to avoid any scarring however trees that are not staked develop stronger trunk and root systems so I use staking rarely
Mulch the base of the tree with organic matter spread around the base of a tree to hold moisture, moderate soil temperature extremes, and reduce grass and weed competition
Water trees unless the soil is waterlogged in which case drain soil. Do so weekly, more in dry weather and high winds.
Talk to them when they are first growing up and encourage them through compliments: they repay you that first chance they are strong enough to be climbed. ALL trees love poems about them
