Care of California Oaks

Native oaks, when young trees, are very tolerant of their environment and make excellent and

adaptable landscape assets. The mature native oak is an invaluable part of our environment but does

not tolerate many changes once established.

Architects, builders, homeowners, and others should be very careful in fitting their plans with these

magnificent giants. Any substantial change in the mature oak’s environment can weaken or kill an

oak, even a healthy specimen.

A good rule of thumb is to leave the tree’s root protection zone (RPZ) undisturbed. This area,

which is half again as large as the area from the trunk to the dripline, is the most critical to the oak.

Many problems for oaks are initiated by disturbing the roots within this zone.

A Word About Roots

Our native oaks have developed survival adaptations to the long, dry summers of most of California.

Primary to this survival is the development and characteristics of its root system. When an acorn

first sprouts, there is rapid root development and very little growth above ground.

This initial root is a tap root extending deep underground for dependable moisture. In fact, the

tree’s first few years are focused on establishing a deep sustaining root system. Once this has

happened, greater foliage and above-ground growth takes place.

As the oak grows, the tap root is outgrown by an extensive lateral root system that spreads

horizontally out from the trunk to and well beyond the dripline, sometimes as much as 90 feet. For

a mature oak, this horizontal root system is the primary supporter of the tree for the rest of its life.

It includes the important fine roots, which absorb moisture and nutrients. Most of the root system

occurs within the top three feet of soil. In shallower soil the root system is concentrated in an even

shallower zone, typically one to two feet below the surface.

As the oak matures, particularly in areas naturally dry in summer, deep-growing vertical roots form

off the laterals, usually within ten feet of the trunk. These sinker roots exploit deeper soil moisture

and add stability to an increasingly massive tree.

By the time a mature oak has established its elaborate root system – so well designed for its

environment and particular site conditions – it has lost the vigor of youth. It is less tolerant of

change and can less easily recover to support a fully developed living structure.

To protect a mature oak, pay particular attention to drainage, and avoid filling, trenching, or paving

near its root zone.

Fill Around Oaks

Soil and other materials placed on top of the natural soil level, called fill, are usually compacted.

They make the soil less permeable, thereby restricting or prohibiting the exchange of gases and

movement of water. Excessive moisture trapped by fill can also cause root and crown rot. Because

there is no guarantee that fill can be safely added around an oak tree, it is best to avoid tampering

with the natural grade, or to leave the natural grade within the root zone alone and use retaining

walls.

Drainage

Poor drainage is a common cause of oak tree deaths, since adequate drainage is critical to ensure a

proper balance of moisture, air, and nutrient to grow and survive. Too much moisture, particularly

in the warm months when natural conditions are dry, can smother the roots and encourage the

proliferation of crown and root rot fungi.

Another moisture threat to oak roots is presented by barriers such as concrete foundations and

footings, streets, and swimming pools downhill of oaks. These structures can dam underground

water, causing water to back up into a tree’s root zone and drown it.

Trenching

Trenching is an often-overlooked cause of tree death. Trenching usually occurs when underground

utilities are installed. Digging a trench for utilities within the RPZ of an oak can sever a significant

portion of a tree’s roots. Often, several trenches are opened by separate utilities. This multi-trenching is particularly destructive since it impacts a greater portion of the root system.

If utilities must impinge on the root protection zone of a native oak, the trench should be dug by

hand, avoiding roots, or utilities bored through the ground at least three feet below the surface.

Paving

Paving can cause the same problems associated with soil compaction. Paving, such as asphalt and

concrete, prevents water from soaking into the soil and impedes the exchange of gases between

roots, soil, and the atmosphere. In addition, paving usually requires excavation to create a stable

base and to allow for depth of paving material. This process compacts the soil and damages roots.

Decking placed on piers is much more compatible with mature oaks than paving.

Care of Established Oaks on Home Grounds

Oaks on home grounds require certain conditions to survive and prosper. Activities of concern to

the homeowner are planting near oaks, irrigation and feeding, pruning, installation of home

improvements, and disease and insect infestations.

Most native oaks in California evolved and prospered in an environment typified by a cool, moist

winter and a hot, dry summer. Under natural conditions, surface soils are wet during the cooler

months and become dry by summer. Natural vegetation growing beneath oaks flourishes during the

winter and spring and dies by early summer, creating the well-known golden-brown landscape of

California’s valleys and foothills.

Native oaks, however, remain green because their thick, leathery leaves and other adaptive features

reduce their water use. The homeowner should attempt to approximate the natural environment in

which these magnificent trees are originally found.

Planting Near Oaks

Only drought-tolerant plants that require no summer water should be planted around old established

oaks, and they should be planted no closer than six feet from the base of the tree. Do not plant

exotic grasses, ivy, azaleas, rhododendrons, or any other vegetation that needs summer irrigation.

Such plants develop thick mats of roots and thus inhibit the exchange of air and water the

established oak has grown used to.

There are a number of plants, some of which are native to California, that can be grown beneath

oaks. For an extensive listing of compatible plants useful for landscaping around oaks, contact the

California Oak Foundation.

In place of plants, other types of ground cover can be used to landscape beneath oaks. When

installed properly, cobbles, gravel, and wood chips are good examples of ground covers that do not

interfere with the roots’ ability to obtain oxygen and appropriate moisture.

Irrigating and Fertilizing

Native oaks usually do not require irrigation as they are well adapted to dry summer conditions.

Healthy oaks are even able to survive the excessively dry summers sometimes brought on by

California’s variable climate. But if an oak has been compromised, as when impervious surfaces

have been placed in the RPZ, occasional water may be helpful if done properly.

Oaks should be irrigated only outside of the RPZ. Under no circumstances should the ground near

the base of a native oak be allowed to become moist during warm weather periods. Moist, warm

soil near the base of a mature oak promotes crown and root rot.

Irrigation, if done, should be by the “deep watering method,” which consists of a slow, all-day

soaking only once or twice during the summer dry period. Frequent, shallow watering not only

encourages crown and root rot, it also results in the growth of ineffective shallow roots near the

surface, a needless waste of the tree’s energy.

If oaks need supplemental watering, it is best to apply the water at times that lengthen the normal

rainy season, so the normal dry period in the middle to the end of summer is preserved. For

example, additional irrigation would be appropriate in May and September, while leaving the area

under the tree dry in July and August.

Mature oaks usually need little or no supplemental fertilization. Light fertilization may be

appropriate in landscaped situations to replace nutrients supplied by leaves and other litter that

normally accumulates under an oak in its native environment. If leaves are allowed to remain under

trees, they eventually break down and supply nutrients.

Fertilization should only be done if growth is poor. Fertilizers should be applied to the entire RPZ,

ideally in late winter or early spring. Trees that have recently undergone severe pruning or root

damage should not be fertilized for at least six months.

Often, when an oak tree shows yellowing leaves, one thinks it lacks nutrients. Generally, this is not

the case. More likely, the tree is suffering from root or crown rot. When an oak appears unhealthy,

consult a certified arborist to determine the cause.

Pruning

Excessive pruning or thinning of limbs may expose interior branches to sun damage, may simulate the tree to produce succulent new growth that is subject to mildew, and, in some cases, may cause a decline in vigor or may kill a tree. Only dead, weakened, diseased, or dangerous branches should be removed.

Necessary pruning should be done during June, July, August and September for evergreen species. Recent research has shown that tree paint, wound dressings, and sealing compounds do more harm than good.

Pruning should be performed by a certified arborist according to the pruning standards of the

Home Improvement

The installation of home improvements should be done with caution when oaks are located nearby.

Trenching severs roots, and impervious surfaces placed over roots may result in the death of the

oak. A swimming pool placed downhill of oaks can act as a dam and cause an oak to drown in

saturated soil.

Great caution should be taken and a certified arborist consulted before proceeding with

improvements that impact on the root protection zone of any valued native oak.

Diseases

When growing under natural conditions, native California oaks are relatively tolerant of most

diseases. However, they are subject to several problems when disturbed or hampered by frequent

summer watering.

The two oak diseases most often encountered in irrigating settings are crown rot and oak root

fungus. Both attack trees weakened by disturbance or improper care.

Crown Rot

This is one of the most common and serious diseases of oaks in home plantings. Infected trees

decline slowly over a period of years. The disease, caused by a microscopic fungus, is made worse

by saturated soil and poor soil aeration.

Symptoms of this disease are a general decrease in tree vigor, twig die-back and wilting, abnormally

yellow leaves, and formation of lesions on the bark accompanied by oozing of dark-colored fluid.

In most cases people notice crown rot too late for successful treatment. However, if the disease is

caught in the early stages a tree can be saved. Comprehensive treatment is best left to a qualified

expert. The following measures usually benefit the tree:

1) Remove lawn and other plants that require summer irrigation from within the RPZ.

2) Remove soil and all other debris that has accumulated against the trunk.

3) Do not water within the RPZ during the summer except under unusual conditions

when advised by a certified arborist.

4) Improve drainage around the tree, and make sure all water drains away from the

trunk.

Oak Root Fungus

This oak fungus, also known as Armillaria root rot, is found in the root systems of most oaks in

California. Our oaks experience little damage from this fungus under natural, dry summer

conditions. However, when oaks are watered in the summer or weakened by other impacts, the tree

can suffer damage from the fungus.

Symptoms shown by an infected oak include die-back of branches and yellowing and thinning of

foliage. The fungus itself may appear as a white, fan-like growth with rhizomorphs and mushrooms.

Prevention of damaging conditions is the only sure action that can be taken against this disease.

Avoid summer irrigation near oaks. Prevent mechanical damage to major roots or root crown. As

with crown rot and other tree diseases, it is recommended that a certified arborist be consulted.

Mistletoe

This parasitic plant grows on the branches of many oaks and can cause structural weaknesses that

make branches more vulnerable to breakage. Its sticky seeds are spread from one tree to another by

birds. The seeds germinate under favorable conditions, and rootlike structures find their way

through the bark, ultimately becoming attached to the oak and tapping into the water-and-mineral conducting tissues of the tree.

Small infestations can be controlled by removing the mistletoe and cutting back the oak’s bark

around the spot where the mistletoe stem entered the oak branch. Major infestations are difficult to

control, however, and an arborist specializing in oaks should be consulted.

Other diseases

The health and vigor of oaks can also be compromised by a number of other afflictions that are not

discussed here. Since 1980, for example, die-back and decline, particularly among the coast live oak

(Quercus agrifolia), has been observed in widespread areas of California. Several fungi may be

involved in this condition, and treatments are still experimental. Seek professional advice whenever

you notice serious, unexplained decline in your oaks.

INSECTS

Innumerable insects find their livelihoods in the branches and leaves of oaks, usually without much

consequence to the healthy tree. The oak gall, for example, is a harmless swelling of leaves and

twigs in reaction to enzymes released where a wasp lays its eggs. Some galls are large and round,

others resemble small wads of fuzz, stars, or tops; one, which looks like a tiny seed, falls from leaves

in the late summer and occasionally jumps into the air like a Mexican jumping bean.

Some infestations, however, can cause serious damage. Insects such as pit scales (which appear as

pinhead-sized scales on the bark of twigs), oak moth and other leaf-eaters can weaken oaks, making

them susceptible to disease.

Whenever an insect infestation causes substantial leaf loss, changes in leaf color, twig die-back,

sticky or sooty foliage and branches, or other significant changes in appearance, intervention may be

required. Consult a certified arborist for assistance.

Who has to pay?

The insurer of the tree-damaged house will usually take responsibility.

If a tree on your property falls and damages your neighbor’s house, your neighbor’s insurer is the most likely party to take responsibility. But this isn’t always so. Exactly whose insurance is responsible will vary depending on whether it’s an act of nature alone or if it was caused by your negligence.

Who Is Responsible

In general, a fallen tree is considered an act of nature that the neighbor’s insurer covers. The negligence issue comes into play if the tree was dying, and your neighbor raised concerns about the possibility of it falling over and you ignored those concerns. In this case, the repair burden falls on your liability coverage. Insurance Company, says a neighbor can prove that she raised concerns by sending you an official letter, prior to the tree falling, warning that you may be held liable for potential damage and sending a copy to her insurer. Without such evidence, it may be difficult for her to prove any negligence.

Make an Appointment with one of our Arborists

Knowing in advance the health and safety of your trees and having them properly taken care of on a regular basis will help prevent future liability issues.

You may need an Investigator

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Deciduous trees or trees that shed their leaves annually enter a dormant state during fall or winter to help them survive the lower temperatures and the lack of water. This is a very good time for winter pruning, also called dormant tree pruning and 90% of the pruning can be done during this time.

The deciduous trees are still alive during winter dormancy. However, with the exception of some root growth when soil temperatures are favorable, the rest of the tree conserves energy by stopping growth  and generally waiting out for the cold season to pass.

To put things in contrast, evergreen can conserve water a lot better and never fully enter dormancy. For that reason, evergreens should be pruned during growth season and not during winter.

What Is Winter Pruning

Winter pruning is the process of removing branches, parts of a branch or stems of a deciduous tree during the cold season when the plan is dormant. Properly done dormant tree pruning encourages growth, can shape the plants at the beginning of their lifecycle and can also improve the overall health of the tree.

When is the Dormant Season?

Trees enter dormancy after they drop their leaves to conserve water and stop growth during the cold season. Generally, in the trees drop their leaves in mid-October, with some tree species such as oaks and beeches keeping their leaves for a little bit longer.

Other factors that trigger dormancy are shorter days/longer nights, the amount of rainfall and a drop in soil temperature.

Long, warm autumns are not necessarily good for the plants, since they can grow new leaves and stems that will be killed by a sudden freeze.

When Does The Dormant Season End

There is no exact date when trees stop being dormant. To complicate things, weather is very unpredictable and might put plants back in eco-dormancy, or dormancy during the time when a plant is ready for growth, but the temperature is still not high enough. In California this occurs mainly in our higher altitudes.

The trees keep track of chilling units, or the number of hours when the temperature is above freezing, with temperatures between 40 to 50 F encouraging the plant to exit dormancy the most.

How Tree Dormancy Works

One of the most important reasons for a tree entering dormancy is water management during freezing temperatures.

There are 2 main ways trees manage water during winter and each one comes with advantages and disadvantages.

The tree keeps water inside their cells, but lowers the freezing point of the water by mixing it with various minerals or hormones. This process, also called supercooling, has the disadvantage of not being to able to withstand very cold temperatures. Even if the freezing point has been lowered, it is sometimes not low enough.

Some trees push water and liquids to the space in-between cells, allowing the water to freeze without damaging those cells. This process also has its own disadvantages, mainly because the tree may become dehydrated.

Winter Pruning Advantages

There are quite a few advantages to winter pruning, and that is why experts recommend the vast majority of pruning to be done during this time.

Sap Activity Changes During Freezing Temperatures

Because of the way how the trees manage water during the winter, new cuts will not ‘bleed’ as much.

The Tree Is More Likely To Increase Its Health

Because of the low temperatures, certain tree diseases and insects that act as pests are less active. Fresh cuts are more likely to attract tree diseases and insects, but not when it is cold outside.

There Is Less Shock To The Tree

Because the tree is dormant, it is not exposed to as much stress as pruning outside dormancy.

You Can Easily Inspect The Tree

With the foliage out of the way, it is easier to see a lot of details such as:

• If the tree has any structural issues
• Identifying dead or diseased areas of the tree and removing them to improve health
• Pruning outside of growth season can prevent the sprouting of weaker shoots and promote stronger growth during spring
• Winter pruning helps to easily identify potentially competing parts of the tree or branches that might represent a safety risk. These parts can be strategically removed by a trained arborist.

You Can Fertilize The Tree At The Same Time

Fertilizing the tree during dormant season benefits the roots as opposed to growing weak shoots.

Dormant Tree Pruning Techniques

There are a few pruning techniques. Some are good and some are bad for the tree (such as tree topping).

Any pruning work should be done with a purpose in mind:

• Safety
• Tree health
• Space management (such as trees that are too close to power lines)
• Disease management
• Pest control
• Air flow
• Getting more sunlight
• Making sure the tree does not compete with other plants
• Shaping the tree

During winter, there are two main strategies you can use to prune dormant trees.

Thinning

It is the process of cutting of a whole branch all the way to the main trunk or to its parent branch. It is used for disease and pest control, or to direct light and improve air flow.

Heading Back

It is the process of removing just part of a branch. There can be no stub left after heading back a branch, because it might rot and attract a host of diseases and insects. To ensure there is no stub left, the branch has to be cut all the way to the next extending side branch or to the next bud.

Winter Pruning Services

So, should you prune your trees exclusively during winter? Not exactly. There are a lot of good reasons to prune trees during spring and summer:

• Some species should be pruned in spring, after they are done blooming
• To increase safety – some pruning cannot wait such as when the tree poses a safety risk to you and your property
• Some minimal pruning to increase the beauty of the tree
• To remove overhanging branches or to make room for something else

As you can see, there are a lot of factors that you have to take into consideration during a winter tree pruning project. The decisions you make will affect the overall health of the tree, it’s structural integrity and the way it will grow in the future. Trees increase your property’s value and healthy trees pose a much lower risk to its safety. That is why it is always a good idea to contact Flintridge Tree Care and our arborist for dormant tree pruning services.

The insurer of the tree-damaged house will usually take responsibility.

If a tree on your property falls and damages your neighbor’s house, your neighbor’s insurer is the most likely party to take responsibility. But this isn’t always so. Exactly whose insurance is responsible will vary depending on whether it’s an act of nature alone or if it was caused by your negligence.

Who Is Responsible

In general, a fallen tree is considered an act of nature that the neighbor’s insurer covers. The negligence issue comes into play if the tree was dying, and your neighbor raised concerns about the possibility of it falling over and you ignored those concerns. In this case, the repair burden falls on your liability coverage. Insurance Company, says a neighbor can prove that she raised concerns by sending you an official letter, prior to the tree falling, warning that you may be held liable for potential damage and sending a copy to her insurer. Without such evidence, it may be difficult for her to prove any negligence.

Make an Appointment with one of our Arborists

Knowing in advance the health and safety of your trees and having them properly taken care of on a regular basis will help prevent future liability issues.

Flintridge Tree Care Training

Philosophy of pruning trees

A properly pruned tree looks as natural as possible; the tree’s appearance reflects its fundamental form and character. The pruner must maintain this structural integrity and know a little tree biology and proper pruning principles.

Recommended pruning equipment

• Hand pruners (Felco or ARS type, bypass, not anvil type)
• long-handled loppers, 18-inch (Corona type, bypass, not anvil type)
• hand-saw, 12–16 inches
• bottle of rubbing alcohol or 10:1 diluted bleach
• whetting stone/sharpener
• oil
• file
• safe ladder (3-legged are best for uneven ground)
• pole pruner, 10-foot (optional)
• chain saw (optional)

Tree Trimming Priorities

1. Maintain the health of the tree
   1. remove all dead, dying, and diseased limbs
   2. remove crossovers, which can rub together and damage limbs and harbor disease
   3. remove hazardous branches before they fall
   4. correct and repair damage.
2. Raise the canopy to increase pedestrian, vehicular or visual zone.
3. Rejuvenate the tree by the removal of old wood in such a way that encourages the formation of new wood (remove no more than 1/3 of the wood in one year).
4. Improve the aesthetic quality of the tree and, thus, its value.
5. Slow the tree’s growth by timely removal of foliage (but best to select the right plant for the site).
6. Fruit trees:
   1. increase fruit production
   2. develop strong 45-degree angles to support the fruit load
   3. remove limbs that grow down or straight up
   4. maintain tree size (5 to 10 feet is ideal size for a home orchard in terms of accessibility)
   5. maintain fruit spurs.

When to prune trees

The best time to prune trees is during the dormant period, usually in late winter from November to March.

The best time to prune trees is during the dormant period, usually in late winter from November to March. Dead or diseased branches should be removed as soon as possible. Pruning done during the dormant season tends to have an invigorating effect on tree growth. Pruning done during peak growth times tends to slow growth by removing leaves that manufacture nourishment. However, too much summer pruning can damage a tree. Pruning during the spring (post-dormancy) and fall (pre-dormancy) is generally the least desirable time as the plant is most vulnerable during those times.

Berries and tree fruits are pruned November until bloom; prune blooming ornamentals during and immediately after bloom.

When you cut away part of a plant, a wound is left, susceptible to pests and diseases. To avoid trouble, always prune so as to make small wounds, rather than large ones. Removing a bud or twig produces a smaller wound than waiting until it is a large limb! Rubbing off a sucker bud leaves a smaller wound than if you wait until it has a year’s growth or more.

Pruning cuts

Heading vs. thinning cuts

A tree’s response to a pruning cut depends on where on the branch the cut is made. Both types of cuts are used in pruning fruit trees and grapes.

• Heading cuts: Several buds left on the cut branch grow, making denser, more compact foliage on more branches. (Figure 1)
• Thinning cuts: Branches are removed entirely, leaving no buds to grow. Their energy is diverted into remaining branches, which grow more vigorously. (Figure 2)

Angle and placement of cuts

Always make cuts close to a node. Branches grow only at these nodes, and if you leave too long a stub beyond the node, the stub will die and rot. (Figure 3)

Prune to the lateral bud that will produce the branch you want. The placement of that bud on the stem points the direction of the new branch. An outside bud, pruned with a slanting cut just above the bud, will usually produce an outside branch. A flat cut above the bud allows two lower buds to release and grow shots.

Pruning thick, heavy branches

1. Undercut the bottom of the branch about a third of the way through, 6–12 inches out from the trunk. (Figure 4, a)
2. Make a second cut from the top, about 2-inches farther out from the under-cut, until the branch falls away. (Figure 4, b)
3. Cut back the resulting stub to the branch collar, not flush with the trunk. (Figure 4, c)

Anatomy of a fruit tree

• Crotch: The angle where branches fork, or where a main limb joins the trunk. Strong crotches are wide-angled, 45 degrees; weak crotches are narrow.
• Scaffold: The main limbs branching from the trunk.
• Watersprout: A very vigorous shoot from a dormant bud on a branch. Remove by cutting.
• Sucker: A vigorous shoot from the roots or from below the bud union. Cut off at the base. (To remove, dig out soil around sucker, clip the sucker off and leave cut exposed to air.)

Parts of the branch

• Terminal bud: The fat bud at a branch tip will always grow first and fastest if you leave it. Cut it, and several buds will grow behind it.
• Leaf bud: Flattish triangle on the side of a branch. To make one grow, cut just above it. Choose buds pointing outward from the trunk so the growing branch will have space and light.
• Flower bud: Plump compared to leaf buds and first to swell in spring. On stone fruits they grow alone or beside leaf buds. On apples and pears they grow with a few leaves.
• Spur: A short twig on apples, pears, plums, and apricots that grow on older branches, produce fat flower buds, then fruit. Don’t remove them.
• Bud scar: A ring on a branch that marks the point where the terminal bud began growing after the dormant season. The line marks the origin of this year’s growth.

Types of tree forms

• Central leader: one dominant trunk all the way to the top; strong, good light penetration; difficult to reach higher branches with large trees
• Modified central leader: central leader trunk to 6 to 10 feet, then multiple leader; combines strength of central trunk with sun-filled center of a vase shape
• Vase shape or multiple leaders: vase shape with many branches; the short trunk of about 3 feet with three or four main limbs, each of which has fully filled-out secondary branches, creating an open center allowing light to reach all branches
• Others: include espalier and trellis

Training for a vase shape

1. First dormant season: After the tree has grown through the spring, summer, and fall and into its first winter dormancy, choose three or four branches with wide (45-degree) crotches, looking for branches that radiate evenly around the trunk. Try to have at least 6 inches vertical distance between branches, with the lowest branch about 15–18 inches above the ground. Cut off the vertical stem just above the top one. (If there are fewer than three good branches, head cut the vertical stem and choose the remaining scaffold branches during the next dormant season.)
2. Second dormant season: If necessary, choose the remaining scaffold branches and cut off the vertical stem just above the highest selected scaffold branch. Remove the weakest side branches from the scaffold branches chosen last season, leaving the main stem and laterals on each branch.
3. Third dormant season: Now is the time to thin surplus shoots and branches. Select the strongest and best-placed terminal shoot near the tip of each scaffold branch, as well as four to six other side shoots on each scaffold (branch). Leave the short weak shoots that grow straight from the trunk, to shade it and help produce food for the tree.

Frequently asked questions

Should I remove my big old apple tree?

Keep it if it has sentimental value, produces good fruit, shades the house, houses a swing or treehouse for the kids. Otherwise, remove it and replace it with several dwarf or semi-dwarf fruit trees. The ideal tree for the home orchard is 5–10 feet; at that height, you are best able to prune, spray, thin and harvest.

(See also EC 1005, Pruning to Restore an Old Apple Tree)

Is it okay to prune suckers and watersprouts? When and how do I do it?

Such overly vigorous growth can be controlled by early summer pruning, which discourages them from regrowing; cut them off at the base. Better yet, rub them off with your thumb in May or June. Watersprouts will emerge following an overzealous dormant season pruning job; sometimes it’s best to leave one or two of these, particularly as a replacement for the leader if it was cut, to discourage regrowth of the others.

Do I need to paint the wounds with a sealing compound?

No, this is no longer recommended. The tree or plant is best protected by proper pruning technique and timing. Sealing compounds encourage wood rot.

How can I slow the growth of a tree?

It is always best to select the right tree for the site, rather than try to work against nature. However, these techniques will help to retard the growth of a tree:

1. Reduce dormant pruning and prune more in June or July. (Winter pruning invigorates a tree; summer pruning decreases vigor and size.)
2. Give no or less nitrogen. Give less water.
3. Hand pull the water suckers in May or June, when they are 2–4 inches long and flexible; this makes it less likely they will regrow. (Pruning suckers in the winter ensures they will regrow in the spring.) Leave a sucker on top of the tree to dominate, called apical dominance.

Should I prune a fruit tree when I plant it?

In digging up a young tree from the nursery, some of the root system can be damaged; top pruning is usually required to prevent tree stress due to the lack of balance between the root system and the top. However, excessive pruning of young trees may delay blossoming and fruiting.

For a single whip, prune tree to waist height at planting. Branching will begin at this pruning cut.

DECIDUOUS TREE TRIMMING

Most deciduous trees should be pruned during their dormant period after leaves have fallen, which is usually October, November, December or January. Such trees include:

* Ash (Fraxinus species)

* Birch (Betula species)

* Cape chestnut (Calodendrum capense)

* Chinese elm (Ulmus parvifolia)

* Chinese pistache (Pistacia chinensis)

* Fruitless mulberry (Morus alba)

* Ginkgo (Ginkgo biloba)

* Italian alder (Alnus cordata)

* Maple

* Sweet gum (Liquidambar styraciflua)

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FLOWERING TREE TRIMMING

Prune flowering trees when they are dormant, if they are deciduous, or immediately after flowering is completed, if they are evergreen. For those trees that bloom when they are leafless, in most cases. 

* Acacias (various species) 

* Bradford pear (Pyrus calleryana, several cultivars), which blooms while leafless

* Camellia Japonica

* Cape chestnut (Calodendrum capense)

* Cassia

* Chinese flame tree (Koelreuteria bipinnata)

* Coral trees (Erythrina caffra and other species), which bloom while leafless

* Crape myrtle

* Empress tree (Paulownia tomentosa), which blooms while leafless

* Firewheel trees (Stenocarpus sinuatus)

* Jacaranda

* Lemon bottlebrush (Callistemon citrinus)

* New Zealand Christmas tree

* Purple orchid tree (Bauhinia variegata)

* Saucer magnolia (Magnolia soulangiana), which blooms while leafless

* Silk tree/mimosa ( Albizia julibrissin)

* Southern magnolia (Magnolia grandiflora)

* Tipu tree (Tipuana tipu)

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FALL & WINTER TREE TRIMMING GUIDE

BROAD-LEAF EVERGREENS TREE TRIMMING

Broadleaf evergreens should be pruned

October, through March or May or June.

Such trees include:

* Bronze loquat (Eriobotrya deflexa)

* Camphor tree (Cinnamomum camphora)

* Carrot wood (Cupaniopsis anacardioides)

* Eucalyptus species

* Kaffir plum (Harpephyllum caffrum)

* Olive (Olea europaea)

* Ornamental figs (ficus species)

* Peppermint tree (Agonis flexuosa)

* Pittosporum species, such as Victorian box (Pittosporum undulatum)

* Toyon (Heteromeles arbutifolia)

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