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• Episode focus: Mastering the veg → flower transition—called the most influential ~10-day window of the cycle. Bad transitions cap yield early; you can’t “add days” later.
• Core idea: Avoid compounding stress. Moving plants is already stressful—don’t stack harsh environmental shifts, heavy pruning/topping, high VPD, and high EC all at once.
• Environment fundamentals
• Lighting / DLI matching: Match day-one flower DLI to veg by increasing intensity (PPFD) for the shorter 12-hour photoperiod.
• Typical targets: ~35–40 mol·m⁻²·day⁻¹ early, ramp to ~45–50 later.
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• VPD matching: Keep VPD close to veg on flip; veg ~0.8–1.0 kPa, then ease into ~1.2–1.4 kPa early flower rather than jumping to dry rooms (1.5–2.0 kPa is too stressful at flip).
• Use VPD strategically to moderate stretch (slightly lower VPD can curb internodal elongation).
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• CO₂: Less finicky but watch costs. Start around ~800 ppm (veg level), 800–1000 ppm in week 1–2, then up to ~1200–1400 ppm depending on style.
• Humidity & red stems
• Many flower rooms lack humidification; day-one rooms run too dry, forcing excessive transpiration and causing stress cues like red stems.
• Plants are humidifiers, but early in flower they’re too small to humidify the room—installing steam/dedicated humidifiers prevents early drought stress.
• EC balance with VPD: High EC + high VPD (e.g., 1.5–2.0 kPa) risks toxicity/lockout. If humidity is good, 3.0 EC is fine; if day-one is dry, start with lower EC until humidity improves.
• “Balance over silos” principle
• Climate (light/VPD/CO₂), root-zone, and irrigation are intrinsically linked. Don’t change one without adjusting the others (“law of minimums” thinking).
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• Canopy management
• Topping vs. no topping: Depends on planting density and cultivar. Topping can delay flower set 3–5 days—costly in a fast crop. Many short/medium cultivars in dense programs perform better untopped.
• Crop registration: Build a simple program to learn genetics (short/medium/tall, heavy/light feeders, topping response).
• Run experiments with new cultivars (e.g., vary drip stakes and leave some untopped) to see true morphology and water response.
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• Defoliation/skirting: Do light skirting in the last 5–7 veg days for airflow and access (easier emitter placement). Avoid heavy defol or topping right before flip—it causes hormonal “whiplash.”
• Trellis best practices: Usually two layers suffice (third is for extremes). Lay both layers in one visit and “hover” the second high, then slide down as plants grow.
• Aim for ~1 top per square; redistribute shoots early before stems get rigid.
• Substrate & rooting strategy
• Common at flip: block-on-slab or block-on-coco.
• Veg-in-place vs. flip immediately:
• Anders’ take: Prefer no veg-in-place if environment is dialed; accept 3–5 days of natural rooting lag (“roots before shoots”) rather than adding calendar time.
• Exception: If day-one flower VPD is too high/dry, consider 3–5 days veg-in-place to avoid compounding stress.
• Requires team precision in irrigation/root-zone control; know your crew’s skill level and market economics (days matter in tight markets).
• Plant readiness (flip criteria)
• Mature root mass fully colonizing its substrate and healthy apical growth—a plant that can handle rapid cell division without collapsing under stress.
• In multi-tier programs, typical veg finish: ~12–18 inches tall with rooted substrate.
• Substrate size trend: Smaller, faster-to-root media (e.g., ~1-gal coco/rockwool); in 2025, 3-gal is “large.”
• Operational pitfalls & lean moves
• Flip too early → low yield density, inconsistent canopy heights.
• Flip too late → light competition, airflow issues, pest/mildew pressure.
• Watch for empty trellis squares—a cue to revisit density or veg time.
• Lean practice: Combine tasks (e.g., apply both trellises once), reduce unnecessary motion.
• Team alignment & checklists
• Synchronize irrigation techs, plant techs, HVAC—use a transition checklist so day-one through day-ten needs are clear.
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• Digital readiness (often forgotten)
• Update track-and-trace (e.g., METRC) plant moves.
• Reset control systems to Day 1 / Week 1 of flower; load verified climate recipes.
• Fill day tanks, flush/clean lines, and set the correct fertilizer recipe.
• Ensure fertigation & climate computers are synchronized on the same day/phase.
• Turn on production tracking (e.g., Aroya harvest tracker) on Day 1.
• Do a quick pass to confirm valves/states are correct.
• Process discipline
• Treat transition as a plant-readiness checkpoint, not a calendar date (when possible).
• Favor small, coordinated adjustments (VPD/EC/irrigation timing) over dramatic single-parameter swings.
• Document & debrief every flip; measure stretch (yes, the humble measuring tape) to inform future runs.
• Wrap-up
• Balance across parameters—not mono-factor tweaks—is what consistently nails the transition and elevates both yield and quality.

ABOUT CULTIVATION ELEVATED:

If you are a grower or owner looking to optimize your existing or new cultivation facility or anyone looking to cultivate more in less space, then this is the show for you. Each week, join Host Michael Williamson as he travels across the country, to explore the world of vertical farming and the future of cannabis and food production through his conversations with leading industry operators, growers and executives who are demonstrating success and resilience as growers and cultivators. Each episode provides stories and key insights that will inspire and show you first-hand, how each of these companies have overcome challenges, and found their own path to success. Brought to you by Pipp Horticulture.

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