General Hydroponics Flora Series Feeding Schedule 2026 (Soil, Coco & Hydro)
Complete General Hydroponics Flora Series feeding schedule — FloraMicro, FloraGrow, FloraBloom week-by-week charts for soil, coco, and hydro. Lucas Formula included.
Why the Flora Series Remains the Industry Standard
General Hydroponics (GH) Flora Series has been the benchmark hydroponic nutrient system since the 1980s. NASA used Flora Series in early space agriculture experiments. It remains the most versatile 3-part system available — the same bottles that work in a basic DWC bucket work in commercial greenhouse operations.
The three-part system:
FloraMicro: The foundation — micronutrients, calcium, nitrogen. Add this first, always.
FloraGrow: Nitrogen, potassium, and secondary nutrients for vegetative growth.
FloraBloom: Phosphorus, potassium, and magnesium for flowering and fruiting.
By adjusting the ratio of these three bottles, you create the exact nutrient profile needed at each growth stage.
Flora Series Feeding Schedule (Full Aggressive Chart)
GH publishes a "light," "medium," and "aggressive" schedule. Below is the aggressive schedule used by experienced cultivators for maximum yield. For first-time growers, start at 75% of these doses and scale up based on plant response.
pH Target: Hydro/Coco: 5.5–6.1 | Soil: 6.0–7.0
Mix order: Always add FloraMicro to water first, then FloraGrow or FloraBloom.
| Week |
Stage |
FloraMicro |
FloraGrow |
FloraBloom |
PPM (500 scale) |
| 1 | Seedling | 2.5 ml/L | 2.5 ml/L | 1 ml/L | 400–600 |
| 2–3 | Early Veg | 5 ml/L | 5 ml/L | 2 ml/L | 700–900 |
| 4–5 | Late Veg | 8 ml/L | 8 ml/L | 4 ml/L | 900–1200 |
| 6 | Transition | 8 ml/L | 4 ml/L | 6 ml/L | 1000–1200 |
| 7–8 | Early Bloom | 8 ml/L | 2 ml/L | 8 ml/L | 1000–1300 |
| 9–11 | Peak Bloom | 8 ml/L | — | 10 ml/L | 1100–1400 |
| 12 | Ripening | 5 ml/L | — | 8 ml/L | 800–1000 |
| 13–14 | Flush | — | — | — | 0–200 |
The Lucas Formula: Simplest GH System
The Lucas Formula is a simplified 2-part approach using only FloraMicro and FloraBloom — no FloraGrow. Developed by a grower named Lucas on cannabis forums in the early 2000s, it remains one of the most trusted minimal-input approaches.
Lucas Formula ratios:
Vegetative: 8 ml/L FloraMicro + 16 ml/L FloraBloom (1:2 ratio)
Flowering: 8 ml/L FloraMicro + 16 ml/L FloraBloom (same ratio — don't change)
Target PPM: 1100–1300 throughout
pH: 5.7–6.2
Why it works: FloraMicro contains enough nitrogen for cannabis regardless of growth stage when used at this ratio. The absence of FloraGrow means lower nitrogen in flower, which cannabis prefers. The simplicity reduces mixing errors.
When to use it: RO water or soft water users get best results. Hard water users should use the hard water version of FloraMicro (GH makes a hard water formula) and may need additional Cal-Mag.
GH Additives: CALiMAGic, Rapid Start, Floralicious
CALiMAGic (3–5 ml/L): Calcium-magnesium supplement essential for RO water users and coco grows. If you're using GH Flora in coco or with RO water, CALiMAGic is not optional — deficiencies will appear by week 3 without it.
Rapid Start (0.5–1 ml/L weeks 1–3): Root development supplement containing plant-derived hormones. Accelerates root branching and speeds early establishment. Worth using in the first 3 weeks then discontinue.
FloraBlend (5 ml/L): Vegan biostimulant with humic/fulvic acids and plant extracts. Improves nutrient uptake and beneficial microbial activity. More relevant in soil than hydro.
Armor Si (0.5–1 ml/L throughout): Potassium silicate supplement that strengthens cell walls, improves heat tolerance, and increases resistance to pests and pathogens. One of the most cost-effective additives available — use from week 1 through week 10.
For a full breakdown of nutrient PPM targets by stage, see our
Cannabis PPM Chart.
Frequently Asked Questions
What is the GH Flora Series feeding schedule for cannabis?
The aggressive GH Flora schedule: Seedling — 2.5/2.5/1 ml/L (Micro/Grow/Bloom). Veg — 8/8/4 ml/L. Transition — 8/4/6 ml/L. Peak bloom — 8/0/10 ml/L. Always add FloraMicro to water first. Target pH 5.5–6.1 in hydro/coco, 6.0–7.0 in soil.
What is the Lucas Formula for General Hydroponics?
The Lucas Formula uses only FloraMicro and FloraBloom at a 1:2 ratio — 8 ml/L Micro and 16 ml/L Bloom throughout the entire grow. No FloraGrow is used. Target 1100–1300 PPM and pH 5.7–6.2. It works for both veg and flower without changing ratios.
Do I need CALiMAGic with GH Flora Series?
Yes if using RO water or growing in coco. RO water strips calcium and magnesium. Coco coir naturally binds calcium, creating deficiencies even with proper nutrient ratios. Add 3–5 ml/L CALiMAGic from week 1. If using tap water above 200 ppm, you may not need supplemental Cal-Mag — test first.
Can I use GH Flora Series in soil?
Yes. Adjust pH target to 6.0–7.0 (versus 5.5–6.1 for hydro). Reduce feeding frequency — water every second or third feeding with plain pH'd water to flush salt buildup. The full 3-part Flora system works well in soil, though simpler options like GH MaxiGro/MaxiBloom are more forgiving for soil beginners.
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