General Hydroponics Feeding Schedule for Cannabis

Growing, buying or possessing cannabis and seeds is legal only in some places. Check the law where you live before acting on this information.

What the General Hydroponics Flora Series feeding schedule is

General Hydroponics publishes a feeding chart for its Flora Series three-part liquid nutrients: FloraMicro (nitrogen, calcium, micronutrients), FloraGro (nitrogen, potassium for vegetative growth), and FloraBloom (phosphorus, potassium, magnesium, sulfur for flowering). The chart specifies exact milliliters per gallon of each component across nine growth stages: seedling, early veg, late veg, transition, early bloom, mid bloom, late bloom, ripen, and flush.

The schedule is published in two main variants:

• Recirculating (for reservoir systems like DWC and RDWC, where nutrients accumulate)
• Drain-to-Waste (for coco coir, soilless mix, or run-to-waste systems, using lower concentrations)

General Hydroponics also provides Easy and Aggressive versions; the aggressive variant targets higher electrical conductivity (EC) and approximates commercial-scale feeding.

Optional supplements mentioned on GH product pages include CaliMagic (calcium and magnesium), Rapid Start (root hormones and carbohydrates), Floralicious Plus, Liquid KoolBloom, and Diamond Nectar.

Why growers use the General Hydroponics schedule

Three practical reasons the Flora Series remains popular for cannabis growers:

Adjustable three-part ratios. Because FloraMicro, FloraGro, and FloraBloom are separate bottles, you can modify the nitrogen-to-phosphorus-to-potassium (N:P:K) ratio by changing the proportion of each bottle. This is more flexible than single-bottle "grow" and "bloom" formulas, which force you to switch products entirely.

Availability and cost. The Flora Series has been in production since the 1970s and is stocked at most hydroponic retailers and online marketplaces ^[1]. A gallon set of the three-part system is affordable and lasts through multiple growing cycles for small to mid-scale home growers.

Documented targets. The published feeding chart and product labels provide exact EC (electrical conductivity) and ppm (parts per million) targets for each stage. This explicit guidance is easier for beginners than estimating nutrient strength.

Importantly, the Flora Series is not demonstrated to outperform comparable nutrient lines in controlled yield or quality trials No data. No peer-reviewed comparative data shows the Flora Series produces higher yields or better cannabinoid profiles than brands such as Jack's 321, Canna, Athena, or MegaCrop. Its value lies in predictability and ease of use, not inherent superiority.

When to start feeding

Seeds and freshly rooted clones carry enough stored nutrients and do not require synthetic feeding immediately ^[2].

Start light feeding when:

• Seedlings have 2–3 sets of true leaves and are actively growing.
• Clones show new leaf growth after transplant into the hydroponic medium, indicating root establishment.

Begin at approximately 25% of the GH chart's seedling column—roughly 0.6 EC or 300 ppm on the 500 ppm scale—and increase gradually over 1–2 weeks Anecdote. Many small growers find the published seedling dosages slightly strong for young plants under LED lighting, particularly when combined with dilute tap water that already contains some minerals.

For photoperiod plants (those dependent on a 12-hour dark period to flower), begin feeding in the vegetative stage once the plant shows vigorous growth. For autoflowering varieties, follow the same leaf-stage cues but expect to transition to early bloom dosing much sooner, often 4–6 weeks after germination.

How to mix and feed, step by step

The order of addition is critical: mixing FloraMicro and FloraBloom together in concentrate will cause calcium and phosphate to precipitate out of solution, locking up those nutrients. Follow this sequence:

Step 1: Use clean water. Reverse osmosis (RO) or filtered water is ideal. If using tap water, test it first to know its starting EC and calcium/magnesium content, which will add to your final target.

Step 2: Add FloraMicro first. Measure the amount from the chart for your growth stage (e.g., ~5 mL per gallon for mid-vegetative). Pour into the reservoir and stir well for 1–2 minutes.

Step 3: Add FloraGro second. Add the specified amount (e.g., ~5 mL/gal for mid-veg) and stir thoroughly for 1–2 minutes.

Step 4: Add FloraBloom third. Add the chart dose even during vegetative growth (e.g., ~5 mL/gal)—the small amount of phosphorus and potassium supports root and stem development.

Step 5: Add any supplements. CaliMagic is beneficial with RO water (typically 2–3 mL/gal, depending on water hardness and plant demand). Add supplements one at a time, stirring between each.

Step 6: Check EC/TDS. Use a calibrated EC or TDS meter to verify you have reached the target. Common targets are:

• Mid-vegetative: 1.2–1.6 EC (600–800 ppm, 500 scale)
• Peak flower: 1.6–2.2 EC (800–1100 ppm, 500 scale)

Step 7: Adjust pH. Add pH Down (phosphoric acid) or pH Up (potassium hydroxide/carbonate) until the reservoir or batch reaches the target pH Strong evidence^[3]. Target 5.5–6.2 for hydroponic and coco systems, which offers the broadest nutrient availability in these media.

Step 8: Feed. In recirculating systems (DWC, RDWC, NFT), add the prepared solution to the reservoir. In drain-to-waste systems (coco, soilless), water plants to mild runoff (10–20% of the volume applied) to prevent salt accumulation.

Stage-by-stage EC reference (approximate, not absolute):

• Seedling / early veg: 0.6–1.0 EC
• Late veg: 1.2–1.6 EC
• Transition / stretch: 1.4–1.8 EC
• Peak flower: 1.6–2.2 EC
• Late flower / ripen (weeks 6–8): 1.2–1.6 EC
• Flush (optional, days 7–10 before harvest): plain pH'd water, 0.1–0.3 EC

Using the chart at reduced strength: If you are new to hydroponic feeding, growing under 400W-equivalent lighting or less, or running autoflowers, run the 50–75% column of the chart rather than the full-strength dose. The published chart assumes strong lighting and mature photoperiod plants.

Common mistakes

Running full chart strength on seedlings or weak lighting. Seedlings and small plants under modest light do not need adult-stage EC. Burnt leaf tips and stunted growth appear within days. Cut to 25–50% of the published dose and increase over 2–3 weeks Anecdote. See Common Beginner Overfeeding Mistakes for details.

Mixing Micro and Bloom together before diluting. Adding concentrated FloraMicro and FloraBloom to each other precipitates calcium phosphate and makes both nutrients unavailable. Always add FloraMicro to water first, stir, add FloraGro, stir, then add FloraBloom.

Ignoring starting water EC. The chart's mL-per-gallon ratios assume near-zero starting water (RO or very soft tap). Hard tap water may start at 0.4–0.8 EC before nutrients are added. Add the chart dose to your water, measure the resulting EC, and adjust downward if needed to match your target.

Not calibrating meters. pH and EC/TDS meters drift over time. Calibrate both monthly using reference solutions to avoid silent errors that cause either overfeeding or apparent deficiencies Strong evidence.

Chasing every supplement. CaliMagic is genuinely useful when using RO water, which lacks calcium and magnesium. Floralicious Plus, Liquid KoolBloom, and Diamond Nectar are advertised as cannabis-specific enhancements, but published trials and controlled data supporting their benefit for cannabis yields or cannabinoid levels are limited Weak / limited.

Long pre-harvest flushes based on folklore. The popular claim that a 14–21 day flush removes residual nutrients and improves taste is not supported by published research Disputed. One controlled trial found no sensory or chemical difference between flushed and non-flushed cannabis. A modest taper (7–10 days of plain water or half-strength feed before harvest) is a reasonable middle ground between folklore and evidence.

Related techniques and troubleshooting

EC and PPM fundamentals. EC (electrical conductivity) and ppm (parts per million) measure nutrient concentration. The two most common ppm scales are the 500 and 700 scales; GH charts default to the 500 scale. Understand which scale your meter uses and convert if needed. EC is more accurate and reproducible than ppm.

pH management. Incorrect pH is the single most common cause of apparent nutrient deficiency symptoms in hydroponic cannabis. Even if you are feeding at the right EC, poor pH causes the roots to absorb some nutrients poorly while blocking others. Target 5.5–6.2 in hydro and coco systems. See pH Management in Cannabis Cultivation for diagnosis and correction.

Coco coir-specific feeding. Coco coir naturally binds potassium and calcium, so plants benefit from slightly higher Cal-Mag supplementation (3–5 mL/gal rather than 2–3 mL/gal) and more frequent feeding (daily or every other day) compared to other hydroponic systems. Use the GH drain-to-waste chart as a baseline. See Coco Coir Growing for full details.

Alternative nutrient programs. Jack's 321 (Jack's 5-12-26 dry fertilizer, calcium nitrate, and Epsom salt) is popular with commercial and advanced home growers for cost, mixing simplicity, and consistency. It requires accurate scaling of dry salts rather than measuring liquids.

Autoflower considerations. Autoflowers progress faster and often show nutrient stress more visibly than photoperiods. Start at 25–50% of the seedling chart and increase cautiously. Many autoflower growers use reduced-strength feeding throughout. See Autoflowering Cannabis Cultivation for stage timing.

Flushing before harvest. The evidence for pre-harvest flushing is limited. If you choose to flush, do so for 7–10 days with plain pH'd water. Do not flush for 14+ days unless you observe severe salt buildup symptoms. See Flushing before harvest and related articles for the science and the folklore.

Sources

How this page was made

Related

• Autoflowering Cannabis Cultivation — Age-based flowering cannabis for faster harvests and simplified growing.
• Building Your Own Feed Schedule — Create a nutrient plan tailored to your water, medium, and strain instead of following man...
• Coco Coir Growing — Soilless growing medium offering root oxygenation and nutrient control for cannabis cultiv...
• Common Beginner Overfeeding Mistakes — How salt accumulation stuns growth and how to avoid it.
• General Hydroponics Flora Series — The three-part liquid nutrient system (FloraMicro, FloraGro, FloraBloom) that became the d...
• pH Management in Cannabis Cultivation — Control nutrient availability by maintaining pH in your growing medium.