General Hydroponics Flora Series

What it is

Flora Series is a three-bottle liquid mineral nutrient system sold by General Hydroponics, a California company founded in 1976 and now owned by Hawthorne Gardening (a Scotts Miracle-Gro subsidiary) ^[1][2]. The three bottles are:

• FloraMicro (5-0-1): nitrogen, calcium, and chelated micronutrients (iron, manganese, zinc, copper, boron, molybdenum).
• FloraGro (2-1-6): nitrogen, phosphorus, and potassium weighted for vegetative growth.
• FloraBloom (0-5-4): phosphorus, potassium, magnesium, and sulfur weighted for flowering.

By adjusting the ratio of the three bottles, a grower delivers a complete N-P-K plus secondary and micronutrient profile appropriate to the plant's life stage. The system is designed for hydroponics but is fully usable in coco coir, peat-based soilless mixes, and even amended soil ^[1].

The label guarantees are public and the formulation has been stable for decades, which is why it shows up as the reference base in countless DIY feed recipes including the well-known Lucas Formula.

Why growers use it

Three practical reasons:

1. Availability and price. Flora Series is stocked in nearly every hydro shop in North America and Europe and is among the cheapest complete hydro nutrients per gallon of finished solution Anecdote.
2. Flexibility. Because the macronutrients are split across three bottles, you can shift the N:P:K ratio continuously rather than switching products at flip. This suits cannabis, which wants more N in veg and more P/K in flower.
3. Documented recipes. Decades of community feed charts exist for Flora Series, including the Lucas Formula (a simplified two-part recipe that drops FloraGro entirely) and General Hydroponics' own "aggressive" and "circulating" charts ^[1].

What it does not do: outperform comparable mineral nutrients like Canna, Athena, Jack's 321, or MaxiBloom in any controlled comparison we're aware of No data. Choice of brand at this tier is largely preference and price.

When to start, when to stop

Start: For seedlings in an inert medium, begin feeding at roughly 25% strength once the first set of true leaves expands. For rooted clones going straight into hydro or coco, start at 50% strength on day one. Seedlings in pre-fertilized soil usually don't need any nutrients for the first 2–3 weeks.

Veg: Ramp from ~50% to 100% of your target EC over the first 2 weeks. Target EC for cannabis in veg is typically 1.2–1.8 mS/cm depending on cultivar and environment Weak / limited.

Flower: Transition the ratio toward more FloraBloom and less FloraGro starting around the stretch (weeks 1–2 of 12/12). Target EC in mid-flower is typically 1.6–2.2 mS/cm.

Stop: Most growers reduce or stop nutrients in the last 1–2 weeks ("flush") to use up stored nitrogen in the leaves. Whether flushing actually improves smoke quality is disputed Disputed.

How to mix it (step-by-step)

Mix in this exact order. Skipping order is the #1 cause of nutrient lockout with this product because FloraMicro contains calcium, and adding concentrated phosphate (FloraBloom) to concentrated calcium causes insoluble calcium phosphate to precipitate out ^[1][3].

1. Start with your water. Reverse osmosis or low-PPM tap water is easiest. If using RO, plan to add a calcium-magnesium supplement only if your feed math shows you need more Ca/Mg than FloraMicro provides — often it doesn't, especially in flower.
2. Add FloraMicro first. Stir.
3. Add FloraGro. Stir.
4. Add FloraBloom. Stir.
5. Add any supplements (silica first if used, then cal-mag, then bloom boosters last).
6. Check EC. Adjust with more water (to lower) or more nutrients (to raise) until you hit your target for the stage.
7. Check and adjust pH. Target 5.5–6.1 for hydro and coco, 6.2–6.8 for soil.

Example mid-flower mix (per gallon)

A conservative starting point — not the bottle's maximum:

• FloraMicro: 5 ml
• FloraGro: 5 ml
• FloraBloom: 10 ml

This lands near EC 1.6–1.8 in RO water and is the basis of the Lucas Formula at the upper end.

Common mistakes

• Mixing out of order. As above — FloraMicro must go in first, fully dissolved, before FloraBloom touches the water. Cloudy reservoirs and locked-out calcium are usually this ^[3].
• Running label strength. The bottle's "aggressive" chart pushes EC well over 2.4 mS/cm. Most modern cannabis genetics burn before they get there. Start at 50–75% of label and let the plant ask for more.
• Adding cal-mag reflexively. FloraMicro already provides calcium. Adding a full dose of cal-mag on top often pushes calcium too high and antagonizes potassium uptake Weak / limited.
• Ignoring EC, trusting ml/gallon. Source water varies. The only number that matters in the reservoir is EC (or PPM) and pH. Measure both every time.
• Not adjusting pH after nutrients. Flora Series drops pH significantly on mixing. Always pH after the full mix is made, not before.
• Buying the 'cannabis-specific' rebrand. General Hydroponics also sells the FloraFlex and CocoTek lines, and competitors sell cannabis-branded versions of basically the same chemistry. The molecules don't know what plant they're feeding.

Related techniques and alternatives

• Lucas Formula: Two-part simplification of Flora Series (FloraMicro + FloraBloom only). Easier to mix, harder to fine-tune in veg.
• Jack's 321: Dry powder, much cheaper per gallon, similar results. Requires more careful weighing.
• Canna Aqua / Coco: Two-part liquid systems tuned for specific media. Pricier, sometimes simpler.
• Athena Pro: Powdered two-part professional line; popular in commercial coco and rockwool.
• Coco coir cultivation: The medium most Flora Series users actually grow in.
• EC and pH management: The skill that matters more than brand choice.

Sources

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