General Hydroponics Flora Series Feed Chart: Expert Feeding Schedule
Whether you are running a DWC hydroponic system or a complex drip irrigation setup, you need a nutrient line that is stable, highly soluble, and perfectly balanced. The General Hydroponics Flora Series is arguably the most famous and widely used 3-part nutrient system in the world. However, its flexibility is also its biggest trap for beginners.
Because you have to mix the three bottles (Micro, Grow, and Bloom) yourself, getting the exact ratios wrong will quickly lead to nutrient burn, deficiencies, and stunted growth. Understanding how to read and execute the general hydroponics flora series feed chart is the difference between a struggling garden and an explosive canopy of heavy fruits and flowers.
Insights Most Growers Overlook
- The “Micro First” Rule: The Flora Micro bottle contains highly concentrated Calcium. If you add Grow or Bloom before the Micro is fully diluted into the water, the phosphorus will instantly bind with the calcium, creating a white cloudy precipitate that your plants cannot absorb.
- The Aggressive pH Drop: These nutrients are extremely acidic. Never adjust your pH before adding the Flora series. Always mix all three parts into your reservoir, let the water circulate for 10 minutes, and then adjust your pH.
- The Lucas Formula Hack: Many commercial growers completely skip the “Grow” (green bottle) entirely. They use an 8ml Micro / 16ml Bloom ratio (per gallon) for the entire plant life cycle. This is famously known as the Lucas Formula and simplifies the feed chart dramatically.
- Hard Water vs Soft Water Micro: General Hydroponics sells two versions of Flora Micro. If your tap water has a starting PPM over 200, you must buy the “Hard Water” Micro bottle to prevent calcium toxicity.
The Golden Rule: Mixing Order Matters
Before you even look at the milliliters on the chart, you must understand the chemistry of the bottles. If you pour all three bottles into a measuring cup together and then dump them into your reservoir, you will instantly ruin the batch. This is called “nutrient lockout.”
The brown bottle, Flora Micro, contains the heavy base elements like Calcium and Iron. If these elements come into direct contact with the concentrated Phosphorus in the Flora Bloom (pink bottle) without being diluted in water first, they chemically bond into an insoluble solid that falls to the bottom of the tank like white snow. Your plants cannot eat solids.
The exact mixing sequence must be:
1. Fill your reservoir with fresh water.
2. Measure and add the Micro (Brown). Stir the water vigorously until it is totally clear.
3. Measure and add the Grow (Green). Stir again.
4. Measure and add the Bloom (Pink). Stir one final time.
The Complete Flora Series Feeding Schedules
The standard feed chart relies on dynamic ratios that shift as your plant ages. During the vegetative stage, the plant demands high nitrogen (from the Grow bottle) to produce lush green leaves. When you flip the lights to trigger flowering, the plant demands extreme amounts of phosphorus and potassium (from the Bloom bottle) to build dense fruits.
| Growth Stage | Flora Micro (Brown) | Flora Grow (Green) | Flora Bloom (Pink) | Target EC (mS/cm) |
|---|---|---|---|---|
| Seedling / Clone (Week 1) | 2.5 ml | 2.5 ml | 2.5 ml | 0.4 – 0.6 |
| Mild Vegetative (Week 2) | 5.0 ml | 5.0 ml | 5.0 ml | 0.8 – 1.1 |
| Aggressive Vegetative (Week 3+) | 7.5 ml | 10.0 ml | 2.5 ml | 1.2 – 1.5 |
| Transition to Bloom (Week 1 of Flower) | 7.5 ml | 7.5 ml | 7.5 ml | 1.3 – 1.6 |
| Aggressive Bloom (Mid-Flower) | 7.5 ml | 2.5 ml | 10.0 ml | 1.6 – 2.0 |
| Ripening / Late Bloom (2 Weeks Before Harvest) | 5.0 ml | 0.0 ml | 15.0 ml | 1.5 – 1.8 |
| Final Flush (Last 5 Days) | 0 ml | 0 ml | 0 ml (Pure Water) | 0.0 – 0.2 |
Reading and Adjusting Your EC Levels
While the chart provides a baseline milliliter dosage, your plant’s environment will dictate how much food it actually eats. If you are growing hydroponic tomatoes under intense LED lights, they will drink massive amounts of water and may require a stronger feed. You must use a hydroponic nutrient calculator alongside an EC/TDS pen to verify the strength of the final mix in the reservoir.
The target EC column in the chart above is your guide. If you mix the recommended milliliters and your EC is too low, you have dilute water and can add more nutrients (maintaining the same ratio). If you mix the nutrients and your EC spikes too high, you must add plain water to dilute the tank to prevent fertilizer burn. You can use an EC/TDS calculator to convert between EC and PPM if your pen only reads parts-per-million.
Special Adjustments for Coco Coir and RO Water
The standard Flora Series is incredibly potent, but it assumes you are using tap water with a base level of trace minerals. If you are using purified Reverse Osmosis (RO) water, or if you are growing in a high-cation exchange medium like coco coir hydroponics, you must modify the chart.
Coco coir naturally binds to Calcium and Magnesium, stealing it away from the plant roots. RO water is completely stripped of these minerals entirely. In both scenarios, you must supplement the feeding schedule with a Cal-Mag (Calcium-Magnesium) additive. Always add 2.5ml to 5ml of Cal-Mag per gallon to the reservoir before you add the Flora Micro bottle to establish a strong mineral base buffer.
| Growth Stage | Cal-Mag Supplement | Flora Micro | Flora Grow | Flora Bloom |
|---|---|---|---|---|
| Vegetative Growth | 5.0 ml | 7.5 ml | 10.0 ml | 2.5 ml |
| Transition (Pre-Flower) | 5.0 ml | 7.5 ml | 7.5 ml | 7.5 ml |
| Aggressive Bloom | 2.5 ml | 7.5 ml | 2.5 ml | 10.0 ml |
| Late Bloom Ripening | 0.0 ml | 5.0 ml | 0.0 ml | 15.0 ml |
| Flush (Last Week) | 0.0 ml | 0.0 ml | 0.0 ml | 0.0 ml |
Balancing the Reservoir pH
No matter how perfectly you follow the feeding schedule, your plants will starve to death if your pH is out of range. The Flora Series is designed to be highly acidic to keep the concentrated minerals dissolved in solution. Once you mix your entire batch of nutrients, let the water pump circulate the tank for 10 minutes, and then perform your final pH management check.
If the pH falls below 5.5, the plants will suffer from magnesium and calcium lockout. If the pH rises above 6.5, the plants will suffer from iron lockout and turn yellow. Use a pH calculator and standard pH Up/Down solutions to precisely hit the 5.8 to 6.0 sweet spot every single time you change the reservoir. Always ensure your water temperature remains below 72°F to keep the pH stable and prevent root rot.
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Written by Sarah Collins
Sarah Collins is a hydroponic grower and horticultural researcher with 8+ years of hands-on experience in DWC, NFT, recirculating, and soil systems. She designs tools and publishes guides at currentgardening.com to help indoor growers optimize their yields.
