Installation and Establishment: ISA Exam Study Notes

Domain Review: This topic is one of the [10 ISA exam domains](/blog/isa-arborist-exam-domains-explained) you must master.

You might think planting a tree is easy: Dig a hole, put it in, fill it up. But on the ISA exam, "planting" is a science called Installation and Establishment. This domain covers everything from selecting the tree at the nursery to ensuring it survives its first few years.

Here are the key concepts you need to know.

1. "Right Tree, Right Place"

This is the mantra of the domain.

• Site Analysis: Before you pick a tree, analyze the site.
  • Above Ground: Wires? Lights? Buildings?
  • Below Ground: Utilities? Soil volume? Drainage? pH?
  • Climate: Hardiness Zone (Cold) and Heat Zone.

2. Choosing Quality Stock

When inspecting a tree at the nursery, look for:

• Good Taper: The trunk should get wider at the bottom.
• Central Leader: (For most shade trees) avoid co-dominant stems.
• Root System: Avoid "circling" or "girdling" roots in container stock.

3. The Planting Hole

• Width: The hole should be 2-3 times wider than the root ball.
• Depth: The hole should be no deeper than the root ball.
  • The Golden Rule: The Root Flare (where the trunk widens into roots) must be visible at or slightly above grade.
  • Exam Tip: If the tree is planted too deep, roots can suffocate (lack of O2) or develop stem girdling roots.

4. Staking

• Old Rule: Stake every tree.
• ISA Rule: Stake only if necessary (windy site, large crown, loose root ball).
• Removal: Stakes should be removed after 1 year (or as soon as the tree is stable). Leaving them too long creates a "weak" trunk because the tree doesn't build reliance wood.

5. Pruning at Planting

• Do NOT: Prune to "balance the crown with the roots." This is an old myth. Leaves produce the energy (photosynthesis) needed to grow new roots.
• Do: Prune only broken, dead, or rubbing branches.

6. Mulching

• Depth: 2-4 inches.
• Placement: Keep it back from the trunk (no "Volcano Mulching"). Mulch against the bark causes decay and attracts rodents.

Summary table

| Concept | Recommendation | | :--- | :--- | | Hole Shape | Wide and saucer-like | | Fertilizer | Generally NOT recommended at planting (slow release if needed) | | Watering | Deep and infrequent | | Wrapping | Only if risk of sunscald, remove after winter |