Rethinking Tree Planting Design

By Phil Woolery

Introduction

The traditional model for tree planting has remained largely unchanged for decades: trees planted in evenly spaced rows at relatively close intervals. While there have been adjustments in spacing to balance self-pruning and growth rates, the core approach has stayed consistent. This design offers clear advantages, including straightforward maintenance and flexibility in selecting crop trees.

However, rising costs—particularly for deer protection and labor—suggest it may be time to reevaluate this system. This article examines conventional planting designs and explores alternative approaches that may reduce costs while maintaining or improving outcomes.

Current Methods

Grid planting with spacing of 8 feet by 8 feet will have a total of 680 trees per acre. This layout allows for easy weed management in the first years after planting. The tight spacing will force the trees to grow straight with good self-pruning.  Some disadvantages of this system include the need for thinning 10 to 15 years after planting. Genetically improved seedlings that are now available can improve growth and future revenue but planting them at this high rate will further increase costs. High deer populations can cause slow growth or failure of tree plantings. Individual tree protection or fencing to protect trees adds significant costs to tree planting.

Increasing spacing is one way to reduce costs. For example, planting at 12-foot by 12-foot spacing reduces density to approximately 302 trees per acre. This lowers both seedling and protection costs while promoting faster growth and extending the time before thinning is required. However, wider spacing reduces natural self-pruning, which may increase the need for manual pruning later.

When these plantings reach the stage for thinning other issues can arise. There is plenty of information on what stocking levels should be at certain sizes and how to do crop tree release. This issue arises when you must apply those practices in your planting.  Landowners may hesitate to remove well-established trees, especially after years of investment in protection and pruning. This indecision can delay thinning and ultimately reduce overall stand productivity.

Lessons from Europe

European forestry has been looking at alternative approaches: cluster or group planting. Somidh Saha, a forest scientist in Germany details his research into cluster planting in a interview the with podcast SilviCast (https://www.uwsp.edu/wfc/wisconsin-forestry-center/silvicast/season-5/an-old-new-idea-cluster-planting/).  Cluster planting was first implemented in the early 1900s in Russia. A range of 25-100 acorns or seedlings were planted in clusters (approximately 20 square feet) and the clusters were separated by around 21 feet. Later modifications of this design in Europe were later implemented. In these designs, around 20 oaks were planted at three-foot spacings, and surrounded by shade tolerant trainer trees. These groups were separated by 30 feet. The space between groups had either trainer trees or early successional vegetation. Research comparing cluster planting with traditional row planting has shown:

• No significant difference in tree height or diameter at 7 and 11 years.
• A higher number of stems with desirable form in cluster plantings.
• No reduction in the number of potential crop trees, despite using about 40% fewer seedlings.
• Lower overall management costs, as weed control and deer protection are concentrated on fewer trees.

Potential Applications

While European planting densities are often higher than those used in the United States, the underlying principle of cluster planting—focused investment in future crop trees—can still be applied effectively.

Consider a typical planting of 680 trees per acre. Over time, this stand may undergo multiple thinnings before reaching a final harvest of roughly 100 trees per acre. Applying equal management effort across all trees can dilute resources, including those spent on trees that will ultimately be removed.

Group planting shifts this approach by concentrating resources on high-value trees from the outset.

Example Planting Design

Planting

• Each group contains 9 potential crop trees planted at 3-foot spacing.
• These are surrounded by trainer species such as river birch, pine, or persimmon.
• Groups are spaced 25 feet apart (center to center), resulting in about 70 groups per acre.
• Areas between groups can remain fallow or be planted with shrubs or additional tree species at wider spacing.

Management

• Focus deer protection and weed control on crop trees within each group.
• Tight spacing promotes good stem form with minimal pruning.
• Begin thinning within groups at years 5–7 to maintain growth rates.
• Select final crop trees by years 10–15.
• Final crop trees will be spaced approximately 20–30 feet apart.

Advantages

• Targeted investment: Resources are concentrated on trees most likely to remain to harvest.
• Simplified decision-making: Each group is expected to yield one crop tree, reducing uncertainty during thinning.
• Improved structure: The layout establishes a clear management framework from the beginning.
• Flexibility: Different species and arrangements can be tailored to site conditions and landowner goals.

There are opportunities to customize the plans for each site and to meet other landowner objectives. The areas between groups can be planted with shrubs to provide food and cover for wildlife. There could be the protentional for some additional revenue from a faster growing species like tulip tree that can be harvested before they start competing with the final crop trees. The number of potential crop trees planted per group could be decreased if you have good survival and management.

Challenges

One limitation of cluster planting is the difficulty of mechanization. Irregular spacing may not be compatible with mechanical tree planters. A hybrid approach—machine planting for trainer trees and hand planting for groups—may be necessary, but this increases labor requirements.

Conclusion

Silviculture is defined as the art and science of controlling the establishment, growth, competition, and quality of forests. Group planting can highlight the creative side of this discipline by allowing the customization of the planting design to meet the site conditions and landowner objectives.

By focusing on long-term crop trees from the outset, this approach has the potential to reduce costs, simplify decision-making, and improve outcomes. While it may require more planning and flexibility, it offers a promising alternative to traditional row-based planting systems.

Source

Saha, S., Kuehne, C., & Bauhus, J. (2017). Lessons learned from oak cluster planting trials in central Europe. Canadian Journal of Forest Research, 47(2), 139–148.