Ask the Expert-Best Practices for Pinching in Horticulture

Pinching is a horticultural tool that can be used to influence plant architecture, branching, flowering and overall crop development. By removing the growing tip, the dominance of the main shoot is removed, changing the hormonal balance of the plant and encouraging the development of more side branches.
Understanding how and when to use pinching is important, as the response can affect not only branching but also flowering time, crop uniformity and the final plant habit.

Key Highlights & Quick Summary

• • What Pinching Does: Removes apical dominance, stimulates lateral branching, creates a compact plant habit, and increases total flower stems.
  • Main Trade-offs: Delays flowering time, temporarily increases plant stress, adds labor costs, and creates open wounds that can elevate disease risk.
  • Trial Results:

    • Salvia SALLYFUN™: Unpinched plants flowered earlier and filled pots nicely. Pinched plants developed up to 4 strong side shoots but experienced delayed flowering.

    • Mimulus MAI-TAI™: Unpinched plants reached first flower in Week 15; pinched plants reached first flower in Week 17 (a 2-week delay).

• What Does Pinching Do to Plant Physiology?

• When the terminal shoot tip is removed, the source of auxin production drops, allowing cytokinins to trigger lateral bud outgrowth.

• Primary Benefits in Commercial Production

• 1. Enhanced Branching: Encourages secondary and tertiary shoots, resulting in higher floral yield.
  2. Compact Habit & Reduced Stretching: Prevents leggy growth, leading to a sturdier plant habit.
  3. Improved Crop Uniformity: Helps align crop height across batch productions when applied correctly.
  4. Maintenance of Vegetative Phase: Keeps plants in a vegetative state longer before flower initiation.

• The Risks and Challenges of Pinching

• Despite its benefits, pinching must be carefully integrated into crop timing models due to potential drawbacks:

• Flowering Delay: The primary side-effect; pinched crops require additional time to reach market readiness.
• • Disease Vulnerability: Pruning wounds serve as potential entry points for fungal and bacterial pathogens (e.g., Botrytis). Handling plants during pinching can also vector diseases across trays.
• • Uneven Growth: Improper or uneven pinching heights can result in erratic shoot growth and non-uniform plant architecture.
• • Increased Production Costs: Manual pinching substantially increases labor requirements per unit.

Case Studies: Danziger Trial Insights

1. Salvia SALLYFUN™ Trial (2026)

A comparative trial was conducted at the Danziger facility in 2026 to evaluate pinched vs. unpinched performance across the SALLYFUN™ series (including Blue Lagoon, Blue Ice, Pure White, Bicolor Blue, and Deep Ocean).

• • March 8 (Pinching Date): Pinch applied to 3 plants; 3 plants left unpinched.

•   March 18 (10 Days Post-Pinch): Unpinched plants were noticeably larger and approaching bloom. Pinched plants were smaller, developing up to 4 side branches.

• • March 22 (2 Weeks Post-Pinch): Unpinched plants began blooming with complete pot coverage. Pinched branches grew steadily, but flowering was visibly delayed.

• • March 30 (3 Weeks Post-Pinch): Unpinched plants reached full bloom on main and side stems. Pinched plants maintained vegetative equivalence but lagged in flowering progression.

• April 6 (Market Ready): Both groups reached market readiness, showing distinct visual differences in shoot density vs. flower timing.

 2. Mimulus MAI-TAI™ Trial

A second Danziger trial examined the influence of pinching on Mimulus MAI-TAI™.
The production process was:

The trial therefore showed a difference in first-flower timing: the unpinched plants reached first flower in week 15, while the pinched plants reached first flower in week 17. Side-by-side comparisons were documented for MAI-TAI™ Red and MAI-TAI™ Orange Imp., comparing pinched and unpinched plants on April 21, 2024 and again on May 1, 2024

Execution Matters: The Impact of Pinch Height

Precision during execution is critical. Commercial observations in Verbena demonstrate that pinching too low in the tray stage can cause lower lateral shoots to completely dominate the canopy.
This creates an unbalanced, unharmonic plant habit that diminishes overall market appeal.

Pinching as a Crop-Management Tool

Pinching is a valuable agronomic tool when used strategically. Much like PGRs, fertilization regimes, and irrigation scheduling, it allows growers to program and fine-tune crop timing and quality.
The key to success lies in balancing the desired benefits – such as improved branching, additional flowering stems, compactness, and crop uniformity – against the operational realities of flowering delays, temporary plant stress, disease exposure, and added labor costs.

Frequently Asked Questions (FAQ)

How does pinching affect flowering time?

Pinching typically delays flowering by 1 to 3 weeks, as the plant needs to redirect energy into developing lateral buds into mature stems before initiating floral buds.

Does mechanical pinching work as well as manual pinching?

Yes, mechanical pinching is widely used in commercial production to reduce labor costs, though precise control over pinch height remains critical to prevent structural defects.

Is pinching necessary for all commercial crops?

No. Pinching should be used as a targeted crop-management tool alongside Plant Growth Regulators (PGRs), irrigation, and fertilization, depending on the cultivar’s natural branching ability and target market window.