Scientific Articles

Title: Exploring Phenotypic and Genotypical Response Through Crop Steering: A Case Study on “Crusty Giant C3”

Author: Stoner Dave | Head Breeder-ReeferMadness Genetics

Over the past two years, the Crusty Giant project has become one of the most coveted strain development efforts under ReeferMadness Genetics. In our ongoing work, we have begun to observe notable results not only through traditional phenotype selection, but also through deliberate manipulation of environmental inputs such as nutrient schedules, light cycles, and training techniques—commonly referred to as “crop steering.”

In the latest phase of experimentation, a specific plant from the third seed in the C-set of Crusty Giant—now dubbed C3—has displayed unexpected and promising variation when compared to its siblings. Initially exhibiting traits that suggested a flowering time beyond 10 weeks, this phenotype responded strongly to intervention.

Techniques Applied:

  1. Nutrient Shift: Switched from the Floraflex dry line to the wet line, resulting in more responsive uptake and easier adjustments to macro/micronutrients during flowering. Additionally, the introduction of Floraflex’s ripening additive before taking clones led to a noticeable reduction in flowering time in subsequent runs.
  2. Training Through Flower: Extensive low-stress training (LST) was carried into the flower cycle, rather than stopping at pre-flower. This appeared to promote longer bud development and more even light distribution.
  3. Light Cycle Manipulation: In the fifth generation of clones, the light cycle was adjusted to 13 hours on and 11 hours off during the first week of flower, then reverted to a standard 12/12 schedule from the second week onward. This approach encouraged additional vertical stretch, which may contribute to increased final yield.
  4. Cloning and Stabilization: Now into the fifth generation of clones, C3 has shown consistent traits across each cycle. The terpene profile, flowering behavior, and overall structure have remained stable after the changes were implemented, reinforcing the fact that genotypical response may be applied to any strain.
  5. Growth Stimulant Addition: In this latest run, Floraflex’s “Bulky B” growth stimulator was introduced at a rate of 1 tablespoon per 10 gallons of feed. This was intended to promote increased bud density and size during mid to late flower.
  6. Irrigation System Change: The current grow features a shift to an automated watering system, now delivering feed 12 times per day, compared to 3–5 times per day in previous cycles. This frequent, smaller volume feeding supports consistent nutrient uptake and root zone hydration. Additionally, implementing one full day of dry back every two weeks has shown increased growth in both lateral and vertical directions.

Environment and Equipment:

  • Lighting: 480w LED from GrowPros Solutions has been used consistently across all three grows.
  • Climate Control: AC Infinity humidifier and fan system manages heat and humidity. An AC unit is also used during summer months to help maintain target ranges.
  • Targets: 78°F temperature and 55% RH are the environmental goals.
  • Canopy Management: Lower branches are removed in a light lollipop-style pruning method. Defoliation in week 3 allows for better light penetration into the canopy.

Terpene Profile Evolution:

One of the most fascinating shifts observed has been the transition in dominant terpenes: originally leaning toward a creamy berry profile, C3 now expresses a creamy and citrus characteristic, suggesting a phenotypic response to crop steering or stress-specific terpene modulation.

Week 4–5 Observations:

During weeks 4 and 5 of flowering in the fifth generation of clones, pistil growth has been closely monitored. Increased pistil development and earlier browning have been observed, suggesting time frame may have not been altered from grows 1 and 2 ending around 50 days slightly. Additionally, top cola growth appears more vigorous than in previous generations at the same stage, possibly indicating improved stacking and final yield potential.

Pollination Timing Insight: With the notable abundance of pistils appearing at the beginning of week 4, this stage presents itself as an optimal window for controlled pollination in future breeding experiments.

Yield and Structure:

  • Plants are showing increased vertical growth in the 12x fertigations per day runs.
  • Nodal spacing remains incredibly tight since the second run, supporting strong structural integrity.
  • Previous runs yielded about 7oz of dry flower per 4ft plant, indicating strong production potential.

Project Direction:

C3 has been removed from the Crusty Giant label in order to be evaluated as its own identity and potential new cultivar. If current trends continue, this line may present new opportunities for breeders and growers seeking phenotypic control through environment—not just genetic sorting.

Future experimentation will focus on maintaining a consistent 7-week flowering time, through light cycle manipulation and nutrient tapering without triggering hermaphroditism.

More to come as information becomes available, stay tuned and enjoy! Much love

HOW TO:

Extend Flowering to 9 Weeks Without Herming

  1. Adjust the Light Cycle Gradually

Start with 13/11 for the first 2-3 weeks of flower instead of jumping to 12/12. Switch to 12/12 from Weeks 4-6 for normal flowering progression. Drop to 11/13 or even 10/14 in Weeks 7-9 to slow ripening without triggering stress. This mimics a gradual fall transition, keeping the plant hormonally in flower while delaying peak ripeness.

  1. Slow Down Phosphorus Uptake (Without Starving the Plant)

Weeks 1-5: Maintain a balanced Bloom formula but don’t push PK boosters early. Week 6+: Slightly reduce phosphorus (P) while maintaining moderate nitrogen (N) and steady potassium (K). Week 8-9: Introduce a mild ripening additive but in small doses (avoiding a hard flush). Keeping P lower helps delay the plant’s internal signal to finish, while moderate nitrogen prevents it from thinking it’s at the end of its life.

  1. Cooler Temperatures & Humidity Control

Day Temp: 74-77°F (23-25°C) Night Temp: 62-65°F (16-18°C) (Cooler nights delay ripening) RH: 50-55% (Prevents drying out too fast) Cooler temps slow plant metabolism, preventing it from rushing to finish.

  1. Maintain Low-Stress Training (LST) & Leaf Management

Light defoliation only in Week 3-4 to improve airflow and light penetration. Avoid major defoliation or pruning past Week 5, which could stress the plant into survival mode. Continue gently bending taller colas in Weeks 5-7 to redirect auxins and extend the bud-building phase.

  1. Prevent Stress That Could Trigger Herming

No excessive drought stress—watering should taper, but never let the plant dry out too much. No heavy nutrient flushing until the last 4-5 days (hard flushing too early signals the plant to rush to finish). Stable dark periods—even a small light leak late in flower could trigger survival-mode pollination.

7 Weeks: Add ripening agent at end of week 6 to ensure a timely and perfect end to the grow. To achieve this is subsequent runs(clones) you can add a ripener before taking the clones and then modifying your light cycle similarly to the Extend to week 9 timing but leave in 12/12 after the change from 13/11.

Shorten flowering time: Add a ripening agent to the mother before taking the clones. This may only need to be done once to “stick” for future clones but it may be cultivar dependent(you might need to do it more than once if you keep taking from the same mother as obviously you don’t want to add ripening agent to a mom normally).