Trees and Summer Flooding

This strange weather we are having may be fatal to your trees!

While it’s true that trees need water to survive, too much water can injure your trees roots.

The top six inches of normal soil is composed of almost equal parts of soil, water and air.

When the soil becomes saturated with water, air is excluded and roots will become stressed.

The amount and extent of damage to the roots depends on several factors. Different species of trees react to flooding differently. The time of year that the flooding occurs also has a direct relationship to the damage it will cause. Another factor is the depth of the flood water and how long it sticks around. These are just a few of the factors to consider.

Flooding in spring along streams and rivers is a normal process and in most years, takes place before the trees have leaves. This type of flooding usually causes little damage for two reasons. The trees are not actively growing so their roots don’t require large amounts of oxygen. The second reason is most river bank, or riparian trees as they are called, have adapted over millions of years to survive this type of flooding. Willows actually have air passages in the tissues of their roots to allow them to survive and even thrive in flooded soils. Damage to trees flooded at this time is often mechanical injury from floating ice, debris or deposition of top soil over their roots. Ash trees will sometimes loose all of their bark up to the high water mark when spring flood waters rise. These types of injuries are often fatal to the trees but are not wide spread. Injuries may go unnoticed as the trees often take several years to ultimately succumb to this damage.

Once the trees have leafed out and are actively growing they are much more susceptible to serious injury from flooding. Temperatures are higher and roots are actively respiring using oxygen in the process of converting carbohydrates to energy. Waste gasses are also lost to the atmosphere and this process is interrupted by flood waters. The roots then start to operate with out oxygen. In this anaerobic state, roots will start to rot quickly if the soil remains saturated. Trees respond by shedding fine feeder roots and shutting down life processes in the larger roots. This in turn prevents the normal uptake of water and the top portions of the tree. The tree will start to exhibit drought symptoms. Leaves will curl and drop and the tree may become completely defoliated. Even though there is plenty of water around none of it is available to a tree without roots. Just as a stranded sailor in a life boat is surrounded by the salty ocean, no water is available to quench his thirst. Trees may die suddenly following this type of flooding or may become weakened and fall prey to other diseases or insects. Trees that are able to survive this type of flooding include, black and green ash, and willow. Trees that may be injured from this type of flooding include, cedars, poplars, cottonwood, birch, Manitoba maple, American elm, hackberry, honey locust, silver maple, bur oak, basswood, buckeye, crabapple, sugar maple, and most pines or spruces. Keep in mind it may take several seasons for the damage to become evident.

Trees that are in shallow depressions may need to be pumped out or drained.

Also when you are pumping out your basement take care that you’re not flooding your valuable trees and shrubs just outside the window.

The Problem With Elm Firewood

Things are happening in your wood pile that you may not be aware of!

That branch from your elm tree that broke off in last winter’s storm or the wood you brought in from the farm may be endangering our stately elms. Drying elm wood gives off a chemical perfume, or pheromone that acts as a beacon for female elm bark beetles. The North American elm bark beetle uses dead or dying elm trees as a site to lay large numbers of eggs. Fresh elm firewood is the perfect place for this egg laying to take place.

“But my tree didn’t have Dutch elm disease, so it should be fine”. The problem is that beetles can be attracted to your firewood from as far as eight kilometers, and if they came from a tree that was infected, all of the thirty offspring from that one beetle will spread Dutch elm disease. A standing dead 12 “tree can produce thirty thousand beetles as it dries out.

Dutch elm disease arrived in North America in the late 1940's from Europe in shipments of raw elm logs. Since that time it has spread west from New York State. Many people may remember a large camper caravan that passed through Southern Manitoba in the mid seventies. The campers stopped in Minnesota on the way and brought elm firewood with them. The next year Selkirk, Winnipeg and Brandon all had their first cases of Dutch elm disease. Many new cases of Dutch elm disease are associated with piles of drying elm firewood. Act now to help protect our stately elms. Check your wood pile for elm wood. If you not sure what to look for, or suspect you may have elm wood, contact your local arborist, or The Provincial Dutch Elm Disease program. Both can advise you on the correct method of disposal for elm firewood. Don’t delay as the new beetles will be emerging in the next few weeks.

If you see some thing suspicious and are in a town that is part of the Provincial Dutch Elm Disease program contact your town office. The Provincial Dutch Elm disease survey crew can be contacted at 1-204-726-6444. Contact an I.S.A. Certified Arborist for the complete story on Dutch elm disease and recommended measures to prolong the life of your graceful elms.

So You Still Want to Plant a Tree

May 17, 2005,

How to dig a fifty dollar hole for a five dollar tree.

The number one mistake made when planting trees is to make the planting hole too small. A properly dug planting hole is broad and shallow, two to three times as wide as the root ball and slightly shallower. It should be dish shaped sloping down to the deepest part below where the plant will sit. Do not place gravel in the bottom of the planting site as this will result in water being trapped in the finer soil on top of the gravel. This is called a perched water table, and often causes root death from drowning. If you site has poor drainage consider installing drain tiles to help improve the situation.

The number two mistake made in planting trees is to plant them too deep.

Roots need to breath, and don’t grow upwards readily. It is much better to plant trees “high and proud” as the saying says, than it is to have buried them in a shallow grave. More than one group of trees of different sizes has been evened up by planting the tallest one a little deeper. Only several years later after the tree has died, does digging it out reveal that it was planted too deep. Roots and tree trunk tissues are adapted to being under and over the soil respectively. The reverse never works. If you see branches coming from below the soil level it’s a tell tale sign that the tree was planted too deep.

Once you have selected your tree and dug your hole its time to put it in the ground.

In the past the most nursery stock was available as bare root, for smaller trees or balled and burlapped for larger landscape feature trees. Container grown trees are a relatively new phenomenon with tremendous advantages, and one big problem. This is the phenomenon of girdling roots. Trees grown in pots will have roots that circle the margin of the pot. When you take the tree out of the pot you will see these roots at the edge of the root ball. It is advised to take a sharp knife and cut these circling roots in a few places around the root ball to limit the chance that they will grow to strangle the trunk of the tree. Girdling roots are much less of a problem with balled and burlapped trees as exposure to air will prune the roots before they get to the edge of the root ball.

Place your tree into the planting hole carefully and fill the soil back into the area surrounding the root ball. The soil should be the same as the soil surrounding the planting site. Mixing back fill soil with peat or sand is not recommended as it creates problems with root penetration beyond the planting hole as the tree grows. The trees roots may never extend past the amended soil. Do not put soil on top of the root ball, don’t bury the trunk. Once your tree is in place and has been backfilled, gently pack the soil around the root ball to eliminate air pockets. Watering after planting is essential to keep the new roots from drying out and to establish a moist link between the planting site and the ground water. If your tree is unstable it may require staking or guying. This subject will take an additional article as it is often done incorrectly. For further advice on tree planting contact an expert, an ISA Certified Arborist.

So You Want to Plant a Tree

May 1, 2005,

The number one mistake made by home owners planting trees is to choose a tree that will be too big for their planting location. Always take into account the mature size of the tree and choose a tree that fits your site. Big site big tree, small site small tree. Look up, way up, are there wires? If so plant a tree that will mature into a small size. Crab apples, cherries, and Asian maples are ideal candidates for small sites. Avoid planting your tree over under ground utilities that may require service or interfere with the roots of the tree. Take our harsh weather into account when planting. All trees moderate the environment and reduce pollution. Large shading deciduous trees planted to the south will shade you from the summer sun while letting winter rays through. Evergreens planted to the north and west can reduce your heating bill. Carefully analyze your site before you select your tree.

Once you have your site conditions figured out chose a tree to fit those conditions. Some trees have a great degree of adaptability to adjust to different site conditions. Shade tolerance, drought tolerance and ability to survive alkaline or flooded soils are just a few potential problems. Adverse site conditions effect the survival of the trees you will plant. Hardiness refers to a trees ability to survive low temperatures. This means not only the minus forty blast of winter but the late frost and May snow storms that we occasionally receive. Native species like the green ash wait until the last frost has passed to send out leaves. Introduced species may be fooled by late winter warm spells. Trees that break dormancy early may be caught with there leaves out too soon. Check to see that the tree you plan to plant is fully hardy. Disease and pest resistance are two areas that must be addressed to avoid disappointment and expensive maintenance in the future. Choose a tree that is healthy and vigorous. Look out for old stock or trees that have just been planted into pots. Once you have crossed all these criteria off the list, you have to pick a tree that has the potential for good branch structure. Be on the look out for weakly attached branches with narrow “v” like crotches. These may fail later in the life of the tree. The process of selecting and promoting permanent branches is easy once you know the basics and will be the topic of a future article. It’s enough to say that all of the branches you have on your 5 to 6 foot tree purchased from the nursery will probably not be there for the life of the tree. Most will be removed while the tree is young for clearance and shaping in the landscape. I guess there is a lot more to planting a tree than just throwing it in a hole!

We will get to actually planting a tree next time, after the snow melts!

Tree Roots Part 2

If the purpose of an inquiry is to dig deeper into the dirt, this article is no exception.

This inquiry uncovers the secret lives of roots.

In our last discussion we touched on the three basic functions of roots:

1) Physical anchoring the above ground portions of the tree

2) Absorbing and transporting water and mineral nutrients

3) Storing starches, sugars and other food reserves

We also introduced the concept of a rhizosphere composed of roughly equal parts of, water, air, mineral soil and a small component of organic matter.

Trees use fine absorbing roots to gain access to minerals dissolved in water that are vital to plant growth. The process by which water is absorbed into the plant is called osmosis. This system is entirely passive. If the root is dryer than the soil it will take in water, much as a dry sponge soaks up a spill. When the root is full of water it stops taking it in.

By the reverse process, when the root is wetter than the soil surrounding it must lose water, much as a wet sponge on a dry surface loses water.

What this means for your tree is that when soil conditions become too dry it will lose water to the soil rather than taking water in. Trees have evolved various methods to maintain water in drought conditions. One way to do this is to shed many fine absorbing roots during periods of drought. The thicker structural roots have a waxy coating that prevents moisture loss and uptake. When conditions permit the fine absorbing roots will be re-grown and the process will begin again. Trees also form beneficial associations with a group of fungi known as mycorizae.

This term translated literally means fungal roots. These fungi grow into the roots and exchange water and mineral nutrition for sugar provided by the tree. This web of fungi around the roots can extend the surface area of the absorbing roots by as much as ten times. Additionally the fungi are better adapted to adsorb soil water when it is in short supply. These fungi are very specific to the types of trees they join in partnership with. Fortunately most soils contain billions of these fungi.

So why do I have roots growing all over my lawn. Roots generally grow downwards guided by a process called geotropism. Gravity drives this process and ensures that roots end up in the soil rather than on top of it. There are two reasons why roots come to the surface. Number one, your lawn is so compacted that the roots are unable to get enough oxygen to allow them to grow at depth. Number two, the constant removal of leaves has interrupted the soil building process. Normally, in a forest setting, roots would be showered annually with layers of leaves and plant debris that would cover the roots and decompose into a rich organic soil.

Soil compaction is the process where air is excluded from the soil by packing the soil particles tighter and tighter. Soil structure is broken down and the soil can become as dense as concrete. Roots have an extremely difficult time penetrating this type of soil. Existing roots will be injured and may not recover from soil compaction. A recent study has shown that six passes over the roots of a tree with a construction tractor will result in the death of ninety percent of the roots in that area. Construction damage effects normally are not seen until three to seven years after the

damage is done. People look out one spring and the trees they bought the house for are dead.

There are things that can be done to prevent construction injury, most are related to preventing

soil compaction.

Tree Roots Part 1

Get Back to your Roots Laddie!

The truth of this statement by a Scottish Kilt salesman, leads us into the largely unseen world of roots.

Roots are the unsung heroes of the plant world. Without the obvious utility of branches or the chromatic charisma of the leaves roots work tirelessly year round.

Roots provide 3 basic functions to a tree:

1) Physical anchoring the above ground portions of the tree

2) Absorbing and transporting water and mineral nutrients

3) Storing of starches, sugars and other food reserves

In addition to these 3 basic properties, roots synthesize important bio-chemicals that regulate how the above ground parts of the tree function.

There are many different types of roots. Trees typically have one or two basic types.

Tap roots are deep probing roots that serve to anchor trees and gain access to deep water resources. Tap roots may extend several meters directly below the trunk of the tree. The burr oak is the classic example of a tap root species. This deep root will be accompanied by many shallower fibrous roots and enable burr oaks to resist drought. Tap roots are the exception in the world of trees; fibrous roots are much more common. Tap roots normally die off and are replaced with lateral roots as trees mature.

Trees like the white spruce and Manitoba maple are good examples of fibrous rooted trees. Large numbers of shallow branched roots extend laterally from the base of fibrous rooted trees. Most often 90% of roots are in the top 150cm, or 6 inches of the soil. This area is called the rhizosphere, in English “the sphere of roots” or “root world”. Roots rely on three essential things in proper proportion in order to grow and thrive. Oxygen, found in the soil atmosphere, mineral nutrition in the form of soil particles, and water are the three basic requirements for healthy roots. Organic material constitutes a forth and smaller component of the soil. The rhizosphere has these components in a balanced proportion.

Pores in the soil are created between soil particles and by living soil organisms. These organisms digest soil particles and each other creating organic matter essential to tree growth. The proportions move in and out of balance as rain water fills pores in the soil and displaces air. Soil compaction can also disrupt the amount of air and water in the rhizosphere. Large tree roots are mainly structural and do not absorb substantial amounts of water or nutrients. The smallest roots are the water adsorbing roots, doing the vast majority of nutrient absorption. These small roots grow and fall off in response to seasonal changes in the soil climate. Winter cold or long periods of saturated soil will result in the loss of many of these small fine roots. Replacing them in the spring or when soil conditions are favorable to root growth is an energy intensive business. All this activity goes on largely unseen by the average person. Things we do above ground will often have negative effects on the delicate balance of the rhizosphere. We will dig deeper into root world in our next column, as we discuss root damage during construction.

How Sunlight Ruins Your Trees

This may come as a surprise, but excessive exposure to sunlight can ruin your trees. Before you rush out to the yard with a backpack full of sun block, consider the following; competition for sunlight is the primary agent that shapes trees in the forest. Without this evolutionary pressure, trees may not have developed into tall, stately plants. Growing tall is energy-intensive business. When competition for sunlight is removed, trees may grow horizontally with large spreading limbs. The tree’s lower branches may touch the ground, looking like the legs of a stool. This appearance is sometimes called stooling. The name actually refers to a method of propagation where some branches may root when they come in contact with the ground. If this appearance appeals to you, you have a unique eye for landscapes. Large lateral limbs on trees may be weakly attached to the main trunk and prone to failure when heavily weighted with snow or ice. What are the solutions to this potentially devastating problem? Timely corrective pruning of young trees is the best approach. Trees grown in landscapes can be trained early, through careful pruning, to limit the growth of large, low limbs. Another option for prevention is to design tree plantings in groups to shade each other, mimicking the natural processes that keep trees growing upright. Unfortunately, these processes can't be implemented on large existing trees. Large cuts on the lower trunks of mature trees usual leads to extensive decay. This decay may cause the trees to fail at the points where the limbs were removed. Careful reduction of large lateral limbs can lessen the impact of eventually removing these large branches. Cabling and bracing, the installation of support rods, and cables or props can reduce, but will not eliminate the risk of limb failure. Put the sun block away and reach for a modern book on tree pruning. If you have a mature tree that has large low limbs that require removal, consult an ISA certified arborist. A small fee paid for a consultation will certainly pay off in the long run.