By: Jean Ferdinandsen, Certified Arborist WI-0149A
Trees are a large component of a home site. Retaining trees in good condition is worth the effort, especially during a construction project.
In order to give your trees their best chance of survival during, and after, construction. Get a Certified Arborist involved early in the process. Develop and follow a tree preservation plan before starting any work.
The main causes of tree decline and death during construction are soil compaction, grade change, and root loss. Even seemingly small activity that compacts or moves soil can kill roots. Soil compaction or fill cuts off air and water to the roots. The damage and stress caused by construction weakens the tree and also sets it up for other issues caused by insects, disease, and drought.
Trees vary in their response to construction depending on species, age, condition, location, and extent of damage. Not every tree should be saved. Focus on preserving healthy young to middle-aged trees, species more resistant to construction, and high value trees.
Decline issues may show up immediately or even up to 10-15 years after construction. Symptoms of decline include:
-Basal suckering or suckering in general.
Decrease in annual growth or leaf size.Wilted or scorched leaves.
-Early fall color.
-Excessive amounts of seed.
The overall goal of tree protection is to minimize root loss. The critical root zone (CRZ) contains 80-85% of the tree’s root mass. Damage within this zone will reduce tree health and survival. Identify and protect the CRZ from construction damage. The CRZ is generally 1.25 to 1.5 feet of radius for every inch of diameter breast height (dbh). For example, a tree that is 20 inches dbh will have a CRZ extending up to 30 feet. Avoid the CRZ as much as possible.
Follow a four-step plan for tree protection:
a. Identify and map trees on the site and determine their CRZ.
b. Predict the extent of damage and make adjustments as necessary to house size, etc.
c. Remove trees within 10 feet of construction.
d. Talk with all contractors to include them in the plan and incorporate necessary access of equipment, cement trucks, utilities, etc.
e. Fence-off CRZs, limit grade changes in the site grading plan to outside of the CRZ.
f. Cushion and protect root zones with six inches of wood chips and ¾-inch plywood for traffic.
II. Pre-condition trees for disturbance:
a. Remove competition from weeds, lawn, etc.
b. Prune out weak or dead branches and those that will conflict with construction.
c. Aerate the soil within the CRZs and prune roots at the boundary of the construction zone.
d. Follow arborist’s recommendations for root zone therapy (fertilizer, root stimulants, compost tea, mycorrhizal fungi, growth regulators, etc.).
f. Water one inch per week .if nature does not provide it.
III. Supervise the construction:
a. Meet with all contractors to obtain their commitment to tree preservation.
b. Maintain the protection measures.
c. Set up penalties for damage to trees.
IV. After care:
a. Commit to long-term maintenance.
b. Maintain mulch and continue watering.
c. Aerate the soil to help mitigate compaction.
d. Protect against insects and disease.
e. Root zone treatments as recommended
f. Prune appropriately and as-needed.
Wachtel Tree Science has decades of cumulative experience regarding trees and construction. Call us before you start your next construction project, to maintain the trees and the value of your property.