8.6 Planting Plans, Plant Schedules & Installation Details

1. Planting Documentation: Schedules, Standards & Calculations

Botanical Nomenclature Standards

Landscape construction documents must adhere to the International Code of Nomenclature for algae, fungi, and plants (ICN):

• Format: Genus (capitalized, italicized) + specific epithet (lowercase, italicized) + 'Cultivar' (capitalized, roman type, enclosed in single quotation marks).
  • Correct: Quercus rubra 'Splendens'
  • Incorrect: Quercus Rubra "Splendens"
• Common names must never stand alone on a planting schedule because a single common name may refer to half a dozen distinct botanical species with radically different soil and moisture requirements.

Nursery Stock Conditions (ANSI Z60.1)

Governed by the American Standard for Nursery Stock (ANSI Z60.1):

Trunk Caliper vs. DBH vs. Height

• Caliper: The standard measurement for nursery-grown landscape trees under ANSI Z60.1. Measured at 6 inches above ground for trees up to and including 4-inch caliper; measured at 12 inches above ground for trees larger than 4-inch caliper.
• Diameter at Breast Height (DBH): Used strictly by arborists and foresters to measure existing mature trees in the field, taken at 4.5 feet (54 inches) above ground.
• Height & Spread: Used for multi-stem small trees, columnar evergreens, and shrubs (e.g., 6–8 ft ht B&B conifer).

Plant Spacing Formulas: Square vs. Triangular Spacing

When planting ground covers or massed shrub beds, plants can be laid out in an orthogonal square grid or an offset equilateral triangular grid:

SQUARE SPACING GRID                      TRIANGULAR (OFFSET) SPACING GRID
      S                                         S
*-----------*                             *-----------*
|           |                             \    / \    /
|   A = S²  |                              \  /   \  /
|           |                               \/  h  \/
*-----------*                                *------*   h = S x 0.866
                                            A = S² x 0.866

• Square Spacing Formula: $\text{Area per plant} = S^2$ $\text{Number of Plants} = \frac{\text{Total Bed Area}}{S^2}$
• Triangular Spacing Formula: $\text{Area per plant} = S^2 \times 0.866$ $\text{Number of Plants} = \frac{\text{Total Bed Area}}{S^2 \times 0.866}$
• The Spacing Constant: An equilateral triangular grid covers ground more evenly and requires 15.5% more plants (1 / 0.866 = 1.155) than a square grid at the identical spacing ($S$).

---

2. Technical Tree & Shrub Planting Details

Field research by modern arboricultural researchers (e.g., Dr. Gary Watson, Dr. Kim Coder) has radically updated technical planting details. Deviating from these modern standards causes premature tree mortality:

                    MODERN TREE PLANTING DETAIL
   No mulch against trunk!                      2" - 3" Shredded Bark Mulch
   (Keep 3"-4" clear)                          (Over entire excavation)
          \                                     /
           v                                   v
        | | |                               . . . . . .
=======/     \=============================*-----------*===== Finished Grade
      / Root  \ <-- Root Flare FLUSH or    |  Backfill |  ^
     /  Flare  \    1"-2" ABOVE grade!     |   Native  |  | Root Ball
    [===========]                          |    Soil   |  | Height
    |   Root    | <--- Top 1/3 Burlap &    |    (No    |  |
    |   Ball    |      Wire Cut & Removed! |Amendments)|  v
    +-----------+--------------------------*-----------*-----
    | Undisturbed Native Subgrade Soil (Prevents Settling)  |
    <---------------- 2x to 3x Root Ball Width ------------->

Key Construction Specifications

1. Excavation Geometry: The planting hole must be dug 2 to 3 times the diameter of the root ball, with sloped sides. The wider the hole, the faster horizontal lateral roots establish into the surrounding site soil.
2. Depth & Undisturbed Base: The depth of the planting pit must be slightly less than the height of the root ball. The bottom of the root ball must rest directly on firm, undisturbed native subgrade. If loose soil is placed beneath the root ball, the heavy ball will settle over time, sinking the trunk below grade.
3. Root Flare (Trunk Flare) Positioning: The root flare—the noticeable swelling where top lateral roots branch out from the trunk base—must be completely visible and positioned FLUSH with or 1 to 2 inches ABOVE finished grade. Planting too deep is the number one cause of premature urban tree mortality; burying the root flare suffocates roots of oxygen and induces adventitious roots that encircle the trunk, becoming lethal stem-girdling roots that strangle vascular cambium.
4. Wire Basket and Burlap Removal: Once the root ball is positioned and secured in the pit, the contractor must cut and completely remove the top 1/3 to 1/2 of the wire basket, all twine, and all burlap. Synthetic burlap, treated burlap, and nylon twine will never rot and must be removed entirely to prevent root constriction.
5. Backfill Soil Physics (No Soil Amendments): Backfill with 100% native excavated site soil. Research conclusively proves that amending the planting hole with rich organic matter (peat moss, compost) creates a sharp textural boundary. Water is held tightly in the fine amended pocket (the "bathtub effect" drowning roots), and developing roots refuse to cross the soil interface into the surrounding unamended native soil, creating a self-rootbound tree.
6. Mulching Standards: Apply 2 to 3 inches of shredded hardwood bark mulch across the entire excavated zone to conserve moisture and suppress weeds. Keep mulch 3 to 4 inches away from the trunk flare. Piling mulch up against the trunk ("mulch volcanoes") keeps bark continuously wet, causing bark rot, fungal infections, and rodent girdling.
7. Staking & Guying Rules: Trees should be staked only when strictly necessary (sites with extreme winds, high vandalism, steep slopes, or loose sandy soils). When staking is required, use broad, flexible webbing straps (never bare wire run through a garden hose) attached loosely to allow the trunk to sway slightly in the wind. Trunk sway stimulates the production of reaction wood (caliper taper) and encourages deep root anchoring. All stakes and guy wires must be removed within one growing season (maximum 1 year) to prevent trunk strangulation.

---

3. Real-World Case Scenario: The Corporate Headquarters Arboretum

Scenario: A landscape architect is detailing a planting plan for a new corporate campus situated on a heavily disturbed former agricultural site in Ohio (USDA Zone 6a). Soil tests indicate heavily compacted clay subsoils with an alkaline pH of 7.8 and severe drainage impedance. The client requests a grand allée of 3-inch caliper shade trees along the entrance drive and a 2-acre naturalized pollinator meadow.

Design Development Solution:

1. Tree Selection for Edaphic Matching: The designer completely avoids Pin Oak (Quercus palustris) due to the 7.8 pH, which would cause severe iron chlorosis. Instead, the designer selects Bur Oak (Quercus macrocarpa) and Chinkapin Oak (Quercus muehlenbergii), both native calciphiles that thrive in alkaline clay soils.
2. Planting Detail Adjustments: To counteract poorly drained clay, the trees are specified with root flares set 2 to 3 inches above finished grade on low, broad earth mounds. The planting holes are specified 3 times the root ball diameter, backfilled entirely with native site soil (no peat moss amendments). The contractor is specified to cut away the top half of all wire baskets and burlap.
3. Meadow Succession & Spacing: The 2-acre meadow is seeded with a mix of native warm-season grasses (Schizachyrium scoparium) and prairie forbs (Echinacea, Asclepias), combined with an oats (Avena sativa) annual cover crop to stabilize the soil during the first year. Ground cover plugs along the building entry are detailed in an equilateral triangular grid at 12 inches on center, utilizing the $S^2 \times 0.866$ formula to ensure rapid visual closure.