047: The Final Push: Dialing in the Last Weeks of Flower

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🌱 Cultivation Elevated – The Final Push: Dialing in the Last Weeks of Flower

Hosts: Michael Williamson & Anders Peterson

Presented by: Pipp Horticulture

Focus: The science and strategy behind the final 2–3 weeks of flower — managing senescence and finishing techniques to maximize chemical quality, aroma, terpene retention, coloration, and smooth burn.

💡 Listen to learn:

• What senescence actually is — and why guiding it matters more than forcing it
• How to taper environmental cues (light, temp, RH, VPD, CO₂) without shocking the crop
• Why extreme “flushing” or 48-hour dark periods are outdated
• How color expression works and when anthocyanins are worth chasing
• The right way to manage root zone EC during the finish
• How airflow, canopy thinning, and uniformity protect quality and drying consistency
• Why trichomes should drive your harvest timing
• Data to track each harvest to refine finishing cycles over time

⏱ Episode Breakdown

Intro: Understanding Senescence

0:00–4:20

• Senescence = the plant’s genetically programmed aging and biochemical refinement phase

• Peaks in cannabinoid + terpene development

• Outdoors, shortening days and cooler nights drive senescence

• Senescence isn’t the plant dying — it’s perfecting what it has built

Why Finishing Matters & Common Late-Stage Mistakes

4:20–7:15

• Growers often stack stressors late (pruning + EC shift + temp change at once)

• Many facilities harvest too early due to tight scheduling

• Early cutting reduces terpene, potency, and maturity

• Final weeks are about refinement, not heavy intervention

Defining a Finished Flower: Trichomes, Pistils & Visual Cues

7:15–11:55

• Trichome progression: clear → milky → amber

• Ideal target: mostly milky, some amber

• Excess new white pistils signal incomplete maturity

• Fan leaf fade = carbohydrates relocating to resin glands

• Avoid sending any late “reveg” signals

Environmental Tapering: Light, CO₂, Temperature, Humidity, VPD

11:55–17:06

• Reduce DLI by 10–25% to avoid photo-oxidative stress

• Taper CO₂ from 1200–1400 ppm down to ~650 ppm pre-harvest

• Lower temps 3–5°F in final week

• Maintain 50–55% RH; avoid deep swings

• Allow modest VPD rise without overdrying

• Cooler late-stage temps help retain volatile terpenes

Color, Anthocyanins & Phenotypic Plasticity

17:06–20:28

• Color = genetics + environment

• Anthocyanins are temp-sensitive and highly plastic

• Some cultivars purple even in warm rooms; others resist

• Extreme cold to force color can reduce yield and slow photosynthesis

The 48-Hour Dark Period Myth

20:28–21:54

• No evidence darkness increases THC

• Benefits come from reduced temperature, not lack of light

• Better: taper light + temp rather than shutting lights off entirely

Drying-on-the-Vine Strategy

21:54–23:54

• Reduce or pause irrigation 12–48 hours before harvest

• Helps start internal drying if dry rooms are undersized

• Avoid wilting; maintain some light for transpiration

Root-Zone & Nutrient Strategy: The Flushing Debate

23:54–29:32

• Full RO flushes cause osmotic shock and reduce yield

• Modern method: gradual EC