Glossary

A fungal rot that starts inside dense buds (brown/mushy core turning to gray fuzz) with the nearest leaf 'flagging' or wilting. Controlled by removing and bagging infected material without shaking, dropping night RH ≤50%, and raising VPD.

A plant, such as cannabis, that fixes carbon via the C3 pathway and loses ~25–30% of its energy to photorespiration at ambient CO₂. This is why CO₂ enrichment to ~1,200 ppm meaningfully raises photosynthetic rate when paired with high light.

A supplemental feed of extra calcium (~150–200 mg/L) and magnesium (~50–75 mg/L) required on RO/soft water and in coco, where CEC binds Ca/Mg away from roots. Its absence causes new-growth Ca deficiency and interveinal Mg chlorosis.

A substrate's capacity to hold and exchange cations (Ca, Mg, K), measured in meq/100 g. Coco is medium-CEC (~40–100) so it buffers nutrients and responds slowly; rockwool has near-zero CEC so its EC tracks feed directly for fast but unforgiving steering.

Raising room CO₂ above ambient ~400 ppm to lift photosynthesis in this C3 crop, typically to 1,000–1,500 ppm for ~20–43% dry-bud gains — but only if light and temperature rise to match. About 1,200 ppm captures ~95% of the benefit; above ~2,000 ppm is diminishing or harmful.

The lab report scoring finished flower on potency, terpenes, moisture, water activity, and microbials before sale. Typical targets are ~18–30% THC, >2% terps for a standout, aw 0.55–0.65, and microbials within limits (Aspergillus action <10,000 CFU/g).

Pre-saturating coco's cation-exchange sites with Ca/Mg (a Cal-Mag or calcium-nitrate soak) before planting so they arrive 'full' and supplemented Ca/Mg stays plant-available. Skipping it causes guaranteed Cal-Mag lockout — the #1 rookie coco failure.

A medium-CEC soilless substrate (porosity ~80%) that behaves like hydroponics but forgives operator error; its non-linear moisture curve makes EC creep, not waterlogging, the dominant failure mode. pH target 5.8–6.2; must be buffered and supplemented with Cal-Mag.

Deliberately pushing the plant toward vegetative or generative metabolism by manipulating root-zone water content, EC, and dryback plus climate (VPD, temp, light). Steering decisions are driven by continuous in-substrate sensor data, not the calendar.

The controlled ~2+ week hold of dried flower in airtight containers (~70–75% full) at ~18 °C and 60% RH, holding internal RH 58–62%, to develop aroma and stabilize the product. Below 55% RH the cure stalls; above 65% mold risk rises. Two-way packs (58%/62%) buffer humidity.

Selective removal of fan leaves to open the canopy for light and airflow, typically a light pass in veg and a two-touch flower schedule around day ~21 and day ~42. Heavy defoliation is avoided deep in the bulking phase.

The total daily photon dose delivered to the canopy, in mol·m⁻²·d⁻¹, calculated as PPFD × photoperiod-seconds ÷ 1,000,000. Cannabis yield responds to total DLI, ranging ~10–20 in propagation up to ~78 at the research ceiling.

The drop in VWC from the post-irrigation daily maximum to the next-day pre-irrigation minimum, expressed as % VWC or % of field capacity. Small drybacks (~5–10% daily) steer vegetative; large drybacks (15–30%) steer generative.

The target finish of the 7–14 day dry at 60–68 °F / 55–65% RH: roughly 75–80% wet-weight loss, stems that clean-snap, ~9–13% moisture, and water activity 0.55–0.65. Temperatures above 40 °C drive terpene loss.

A measure of dissolved salt/nutrient concentration, in mS/cm (=dS/m). Feed EC runs ~0.5–0.8 at clone up to 2.0–2.8 in flower (HPS 3.0–3.5, LED 3.5–4.0); lower EC steers vegetative and higher EC steers generative.

The maximum VWC a substrate holds before it begins shedding leachate. Coco commonly sits ~45–65% VWC; rockwool has a consistent FC measured with a saturation test, and each substrate batch should be measured rather than assumed.

A steering strategy that pushes flower initiation, density, and terpene/resin expression via lower water content, higher EC, large drybacks, fewer large shots, minimal runoff, higher VPD, and cooler air. Used in stretch and ripening.

A mechanically transmitted viroid ('dudding disease') that silently cuts cannabinoids/terpenes ~50% and produces stunted, brittle plants with airy loose buds. Diagnosed by RT-qPCR on root tissue; managed by roguing, TC remediation, and sterile single-use blades.

The daily fertigation cycle across the 24-h photoperiod: P0 overnight/pre-irrigation dryback, P1 morning ramp to field capacity, P2 midday maintenance shots, and P3 the overnight dryback after the last shot. Larger P3 dryback is a generative cue.

The actual temperature of the leaf surface, which under LED runs ~1–3 °C (≈2–4 °F) cooler than air. Because VPD is a leaf-surface phenomenon, computing it from air temperature alone overstates VPD, so leaf temp should be measured (IR gun) or assumed at −2 to −3 °F.

The intensity at which added light stops increasing photosynthesis. A key Bugbee finding is that while single leaves saturate below ~400–800 µmol, whole-canopy cannabis yield does NOT saturate within practical indoor limits, rising near-linearly to ~1,800 µmol PPFD.

Stripping the lower larf (small underneath growth) off plants pre-flip so the plant redirects energy to the top-canopy bud sites that receive full light. Part of the standard commercial recipe of top + LST + SCROG + lollipop.

The seed-to-sale compliance system using unique, non-reusable RFID plant and package tags (100-clone batch tags, individual tags at veg) that must be reconciled within days of every move, harvest, or waste event. Unreconciled variances are among the most-cited violations.

Whether a nutrient can relocate within the plant, which dictates where deficiency appears. Mobile nutrients (N, P, K, Mg, Mo) show deficiency on old/lower leaves first; immobile nutrients (Ca, S, Fe, Mn, Zn, B, Cu) show it on new/upper growth.

The 400–700 nm waveband of light that drives photosynthesis; ePAR extends the definition to ~750 nm because far-red drives photosynthesis synergistically. It defines which photons 'count' for plant growth.

The acidity of the feed and root zone that governs nutrient availability; targets are 5.8–6.2 in coco and 5.5–6.0 in rockwool. Drift above ~6.5 locks out Fe, Mn, Zn, and B, so most field 'deficiencies' are actually pH-driven lockout.

When nutrients are present in the feed but unavailable because root-zone pH is out of range — e.g., pH above ~6.5 locking out Fe, Mn, Zn, and B. It mimics true deficiency, so pH and EC should always be confirmed before dosing more nutrients.

The number of PAR photons a fixture delivers per watt of electricity drawn — the single most important fixture spec for ROI. HPS runs ~1.7 µmol/J versus ~2.5–3.0+ µmol/J for modern white+red LED.

A fungal disease appearing as white powdery circular colonies on upper leaf surfaces that wipe off and return, favored by RH >55–60% and stagnant air. Controlled by keeping RH <55%, airflow, and K-bicarb/sulfur; treated as zero-tolerance on flower.

The instantaneous density of photosynthetic photons hitting the canopy, measured in µmol·m⁻²·s⁻¹. Typical targets run ~150–300 for clones, 300–600 in veg, and 600–1,500 in flower depending on CO₂.

An inert, sterile, homogeneous slab substrate with a near-linear water-release curve, making it the most steerable but least forgiving medium. Has near-zero CEC, needs low-pH conditioning, and must never dry below ~25–30% VWC or it goes hydrophobic.

The nutrient solution that drains from the substrate after irrigation; its EC and pH reveal what is happening in the root zone. Runoff should read roughly feed EC + ~0.3 mS/cm — much higher means salts are stacking. Coco targets 10–20%, rockwool 5–25% depending on steering.

A trellis-net training method installed in late veg (weeks ~3–5) with tops woven to fill ~70–80% of the screen before flip, locking an even canopy for uniform light penetration. Commonly cited at 2–3× yield versus untrained plants.

The volume of a single irrigation event, expressed as a percent of substrate volume (a '3% shot' raises VWC by ~3%), typically 2–6%. Vegetative uses many small shots (shot > dryback); generative uses fewer large shots (shot ≈ dryback).

Neutralizing rockwool's native alkalinity before transplant by soaking ≥24 h in a pH 4.5 (never below), EC 0.5–0.6 mS/cm solution, then stabilizing to pH ~5.5 and EC 0.4–0.5. Going below pH 4.5 dissolves the fiber structure.

A hot-and-dry-loving pest causing pale stippling on the upper leaf surface that progresses to bronzing and fine webbing, working from the lower canopy undersides up. Confirmed with a 10–14× loupe and acted on at first webbing; controlled with predatory mites like P. persimilis.

The rapid vertical elongation phase in the first ~3 weeks of flower after the 12/12 flip, during which plants can roughly double in height. Growers steer generative and ramp PPFD as the canopy fills; peak light is reached during or after stretch, not at flip.

Heat-treating blades to 160 °C for ~10 min between plants (140 °C is insufficient) or using dedicated single-use tools to stop mechanical viroid spread. Chemical dips like bleach, Virkon, and ZeroTol do not reliably inactivate HpLVd.

A high-stress veg-only training cut above node ~3–4 that splits one apical tip into multiple colas; requires sterile tools and a 3–5 day recovery before resuming LST. Multiplies cola sites for a wider, more even canopy.

The evaporative water flow from roots out through leaf stomata that cools leaves, keeps stomata open for CO₂ uptake, and pulls the water-plus-nutrient stream up from the root zone. Mass-flow nutrients like calcium and boron depend on steady transpiration.

The golden rule of P1 timing: the first drain of the day should occur during the active transpiration window, not at lights-on. Watering before the plant is transpiring waterlogs roots at the coldest, least-active point of the day.

The primary harvest-window indicator, judged on calyx gland heads under a 30–60× loupe: ~80–90% cloudy plus 5–15% amber marks peak THC. Pistil browning (70–90%) is corroborating only.

The standard split of a nutrient base into Part A (the nitrate/calcium side) and Part B (the phosphate/sulfate/potassium side), kept separate in concentrate because concentrated calcium plus phosphates/sulfates precipitates insoluble gypsum. Combined only diluted in the mix tank.

A steering strategy that pushes root/leaf/stem growth, stretch, and recovery via higher water content, lower EC, small drybacks, frequent small shots, higher runoff, lower VPD, and warmer root zone. Used to build canopy and to bulk flowers mid-bloom.

The drying power of the air at the leaf surface, in kPa — saturation vapor pressure at the leaf minus the air's actual vapor pressure. It is the true driver of transpiration; targets run ~0.4–0.8 in propagation, ~0.8–1.2 in veg/early flower, and 1.2–1.6 in late flower.

The volume of water divided by total substrate volume, expressed as a percent, read continuously by in-substrate sensors. Higher VWC steers vegetative and lower steers generative; it is the primary irrigation metric.

A measure of free (microbially available) water in dried/cured flower on a 0–1 scale — the key stability and compliance metric. Targets are 0.55–0.65 aw for finished product (USP 0.60 ± 0.05); above ~0.65 invites mold, below ~0.55 stalls the cure.