These pages are meant to be an open forum for your discussions of anything horticultural in nature. Please feel free to contact us with your thoughts or concerns of our horticultural world here on the north Oregon coast.
Aphids' feeding on the spruce needles cause them to dessicate and fall off of the tree. These photos show a couple of aphids found feasting in Nehalem, OR (note the yellowish discoloration where the lower aphid is feeding in the photos below).
A very invasive weed impacting our area
is knotweed. This non-native weed was introduced to America from Asia
a century ago, and has since spread across the nation. This noxious weed
is very difficult to control, and spreads vigorously when mowed. We are
currently working with the city of Manzanita to control this weed within
city limits. Direct-injection of herbicide into knotweed canes is proving
very effective. Please help inform your neighbors with knotweed to avoid
mowing this weed.
Ecologically speaking…building with trees.
Preventing Construction Damage
Sometimes it seems we see trees as solid, invincible objects impervious to human influence. On the contrary, trees are dynamic living organisms that can easily be wounded or injured. Like all living organisms, trees are healthier in favorable environments and suffer in unfavorable conditions. Damage to trees happens often during building construction as their living environment is altered. Even when sincere attempts to preserve trees are done incorrectly, the trees still suffer.
There are many cases where a home was built around a tree with good intentions of preservation. Unfortunately, if the builder lacks knowledge of tree physiology, construction impacts still cause injury and decline. The damage done to trees can go unnoticed for several years as the tree survives on carbohydrate reserves stored within. After time has passed, and the damage is done, is often the first time an arborist is called in to explain why the tree is dying or “not looking good”. How can we increase the survival rate of trees impacted by construction? The best chance begins with collaboration of the owner, builder, and arborist all working together from the project’s inception. Following current industry guidelines for tree preservation can help prevent inadvertent loss of trees during building. These guidelines set standards for minimizing the impact to trees and mitigating the effects of construction that do occur.
There are several methods by which trees can be damaged during development.
* Soil compaction.
Up to 80% of tree injury during construction occurs below ground. The most common, yet often overlooked, is soil compaction. Pore spaces within soil contain both oxygen and water, which roots absorb along with minerals and nutrients. Ideal pore space volume in soil is around 50%. When construction equipment and hundreds of footsteps pass over a building site, much of this valuable pore space is lost. Keeping construction processes out from underneath a tree’s drip line will prevent this issue. Physical injury to tree trunks and limbs is also avoided when trees are not encroached upon.
Surprising to some, 90% of a trees roots are found within the top 2’ of soil. Most of the fine roots used to absorb water and nutrients are found within the top 8-12”. When even the slightest excavation occurs below a tree, root damage occurs. The best choice for tree health is to avoid this area altogether, but locating structures on urban lots often makes this unrealistic. To minimize damage to a tree’s critical root zone, clean cuts should be made to roots 1-2” and larger. Ripped and torn roots cause dieback, and increase the potential for root rot or other pathogens to invade. After excavation, pruning torn roots to smooth cuts allows the tree to more easily seal this wound; new roots will also grow from this point. When placing utility lines, tunneling beneath the root system greatly reduces the damage caused by digging trenches.
Sloping lots and uneven terrain are usually graded level or backfilled with foreign soil; both circumstances alter a tree’s chance of survival. Depositing more than 6” of fill-soil above original grade can smother the root system, depriving it of oxygen. The added soil also holds moisture against the trunk flare, where the trunk meets the soil, and often causes issues of root rot infection. One method of mitigating this damage is to create a tree-well around a tree to be preserved. A simple well built around the tree’s trunk should leave at least 6-12” of space around the exposed trunk flare, and be built higher than the new grade. Drain pipe is then place along the tree’s structural root system and vented to above the desired grade, allowing for increased oxygen filtration to the buried roots.
Since some trees simply have to be removed on many building sites, those that remain may suddenly become exposed to new environmental elements. Trees growing close together usually share a combined root system and grow taller as they compete for light. Opening up this forested environment exposes previously sheltered trees to increased wind loads, and shaded trees to potential sunscald damage. Preserving stands of trees in groupings, or tree islands, can usually help alleviate this problem.
Trees damaged by construction often become more susceptible to infestation. As the tree struggles to survive and adapt to its new environment, its natural defense mechanisms become compromised. In this weakened state, insect and disease pathogens can infect the tree and cause further decline. Keeping your trees healthy during and after site development is fundamental to preventing pathogen attack. Different tree species react differently to various environmental stresses and proper planning of your tree preservation methods are important.
Preserving large mature trees can be more challenging, as younger trees are more adaptable to change. However, successful tree preservation projects can be accomplished when you begin with a comprehensive plan. Beginning your construction project by including an arborist with your design and architectural team is advantageous to all. Your arborist may begin with a site inspection and tree survey to identify both hazard trees and those best suited for preservation. Discussion between your arborist and architect can lead to a building plan designed to balance facilitating construction with tree preservation. Making the tree locations and root-zone protection areas evident on all relevant blueprints should help ensure your building crews understand your goals. Orange construction fencing placed around the critical protection areas is designed to be an obvious deterrent to construction crews. Someone may still need to be assigned the responsibility of enforcing your protection plan.
Once the homeowner, designers, and builders are all committed to the same goals, a successful project will likely follow. Efforts to ensure tree preservation will more than offset the cost of benefits these trees provide. The cost to remedy construction damage in the years following impact greatly increases, while the trees suffer and decline. Trees that must be removed can be recycled onsite; by spreading woodchips to reduce compaction or including felled logs into the home’s design. With proper planning and design, you can keep the dead lumber in the framing and not in the forest. You will be truly…building with trees.
Contributed by David Sip, of Manzanita, an ISA Certified Arborist. Please direct questions or comments to email address: firstname.lastname@example.org. Source references for data provided herein are available upon request.
**Originally published in Cannon Beach Gazette and North Coast Citizen's "realizing your HOME & home enhancement" insert volume #5. Published under heading: "Building among trees challenging, but doable". Release date: 5-29-06.**
Arbor day is, by no accident, timed with the birth of spring as we slowly trudge our way out of winter.