General Hydroponics Flora Series Review: The Industry Standard

The short version: The General Hydroponics Flora Series is the most proven three-part nutrient system in hydroponics. It works across a wide range of crops, it’s well-documented, and the mixing ratios are forgiving enough for beginners while flexible enough for experienced growers to dial in. At $35–45 for a set that lasts months, it’s also genuinely affordable. If you’re not sure what nutrients to use, start here.

Why the Flora Series Has Lasted 40+ Years

General Hydroponics was founded in 1976 and introduced the Flora Series as one of the first commercially formulated, three-part hydroponic nutrient systems. That was not a small thing — before systematic formulations like the Flora Series, hydroponic growers were mixing nutrients manually from industrial fertilizer sources, which required considerably more expertise.

The Flora Series solved the formulation problem and made consistent results accessible to hobbyists and small commercial growers. NASA used it for plant growth experiments in space. Commercial lettuce and herb operations use it today. Home growers have been producing reliable harvests with it for over four decades.

That track record is the most important thing to understand about the Flora Series: it works, it’s been proven in an enormous range of conditions and crops, and virtually every hydroponic question you can ask about it has already been answered online. That last point alone is worth something when you’re troubleshooting at 11pm and your plants are showing deficiency symptoms.

View the General Hydroponics Flora Series on Amazon →

The Three Bottles and What They Do

The Flora Series comes in three components. Each addresses a different nutritional need, and you combine them in different ratios depending on your crop and growth stage.

FloraMicro — The Base

FloraMicro is the foundation of every Flora Series mix. It contains:

Nitrogen (in both nitrate and ammonium forms for balanced uptake)
Calcium
Trace elements: iron, manganese, zinc, boron, copper, molybdenum

Calcium is in FloraMicro rather than the other bottles because calcium and certain other nutrients create precipitates when mixed at high concentration. By keeping calcium here and adding it to water first (before the other components), you avoid the common “calcium lockup” problem that plagues poorly formulated nutrients.

Key rule: Always add FloraMicro to water first, before FloraGrow or FloraBloom. If you combine FloraMicro and FloraBloom directly, you’ll get a white precipitate that’s essentially useless — the nutrients have locked up and won’t be available to plants.

FloraGrow — Vegetative Growth

FloraGrow is nitrogen-heavy with added phosphorus and potassium. It supports:

Leaf and stem development
Root system expansion
Vegetative growth during the early and mid phases of a plant’s life

For leafy crops like lettuce, herbs, and spinach — which never transition to a true fruiting/flowering phase — FloraGrow stays as the dominant component throughout the grow.

FloraBloom — Fruiting and Flowering

FloraBloom shifts the nutrient balance toward phosphorus and potassium, which fruiting plants need when they transition from vegetative growth to producing flowers and fruit. Less nitrogen, more P and K.

For herbs and leafy greens, FloraBloom plays a supporting role. For tomatoes, peppers, cucumbers, and strawberries, it becomes the dominant bottle as plants start to flower.

How to Mix It: The Beginner-Friendly Ratios

General Hydroponics publishes a full mixing chart, but most beginners don’t need all of it. Here are the practical starting points:

For leafy greens and herbs (per gallon of water):

5 ml FloraMicro
10 ml FloraGrow
5 ml FloraBloom

This produces a balanced solution at roughly 1.0–1.5 mS/cm EC — appropriate for basil, lettuce, parsley, cilantro, spinach, and mint.

For seedlings and early growth (per gallon):

2.5 ml FloraMicro
5 ml FloraGrow
2.5 ml FloraBloom

Half-strength at the seedling stage prevents nutrient burn while plants establish their root systems.

For fruiting crops in the flowering/fruiting stage (per gallon):

5 ml FloraMicro
5 ml FloraGrow
10 ml FloraBloom

Shift toward FloraBloom as you see the first flowers forming.

The golden rule: Mix into water in this order — FloraMicro first, FloraGrow second, FloraBloom last. Stir or circulate between each addition. Check EC, then check pH.

Target pH for most crops: 5.5–6.5. Use pH Up or pH Down to adjust after mixing. See our full guide on hydroponic nutrients for beginners for more detail on EC and pH management.

What It Actually Grows Well

The Flora Series is genuinely versatile across crop categories. Here’s what you can expect:

Herbs: Excellent. Basil, parsley, cilantro, mint, thyme, chives, oregano — all grow reliably well with the vegetative-focused ratios. Herbs are fast-cycling and forgiving, and the Flora Series gives them what they need without complexity.

Leafy Greens: Excellent. Lettuce, spinach, kale, arugula, Swiss chard — the Flora Series is used commercially for lettuce production for good reason. These crops reward consistent nutrient delivery and the Flora Series delivers.

Tomatoes: Very good. The ability to shift ratios toward FloraBloom during flowering is exactly what tomatoes need. Cherry tomatoes do well in countertop systems; larger varieties need more root space.

Peppers and Cucumbers: Good. Same approach as tomatoes — vegetative-focused early, then shift toward FloraBloom. Results are better with systems that have strong light output.

Strawberries: Good for everbearing varieties. The Flora Series provides the P/K balance strawberries need for continuous fruiting.

Flora Series vs. FoxFarm Trio

The most common comparison to the Flora Series is FoxFarm’s liquid nutrient trio (Grow Big, Big Bloom, Tiger Bloom). Both are three-part systems, both are widely used, both work.

The key differences:

Synthetic vs. organic-blend: The Flora Series is fully synthetic — pure mineral salts in precise ratios. FoxFarm’s nutrients contain organic compounds alongside synthetics (fish meal, kelp, bat guano). The organic components can support slightly more microbial activity and give aromatic herbs a bit more complexity in flavor.

Reservoir cleanliness: Flora Series runs clean. The reservoir stays clear, algae is easier to prevent (since there’s no organic matter to feed it), and the system is easier to maintain between reservoir changes. FoxFarm can cloud your reservoir and requires more frequent cleaning.

pH stability: Flora Series is more pH-stable after mixing. FoxFarm with organic components can cause more pH drift, requiring more frequent testing and adjustment.

Cost per gallon: At the mixing ratios above, the Flora Series works out to roughly 10–15 cents per gallon of prepared nutrient solution. FoxFarm is in the same range. Masterblend (dry concentrate) beats both on cost if you’re scaling up.

Verdict: For a countertop system or any setup where reservoir cleanliness matters, the Flora Series is easier to manage. If you’re growing in a dedicated grow tent and prioritize organic inputs, FoxFarm is a legitimate alternative.

How Long a Bottle Set Lasts

At the mixing ratios above (20 ml total per gallon), a standard 1-liter set of Flora Series nutrients will make approximately 50 gallons of prepared solution. For a countertop system with a 1.5-gallon reservoir changed every two weeks, that’s around 1.5+ years of growing from one set of bottles.

This is part of why the Flora Series represents such good value. The $35–45 price tag isn’t a frequent recurring expense — it’s a one-time purchase that covers a long growing season.

What the Flora Series Doesn’t Do

A few limitations worth knowing:

No pH buffering. You need a pH meter and pH adjustment solutions. The Flora Series doesn’t auto-correct pH. This isn’t unique to General Hydroponics — no mainstream nutrient system does this automatically (Advanced Nutrients makes a “pH Perfect” claim that’s somewhat marketing-inflated). Budget for pH Up, pH Down, and a basic meter.

Not organic-certified. If you’re growing for organic consumption specifically, the Flora Series isn’t certified. FoxFarm or a true organic concentrate would be the alternative.

Three bottles means three things to measure. Compared to a simple one-part formula, the Flora Series does require more measuring. The ratios are straightforward, but if you’d prefer to shake one bottle and pour, there are simpler options (though with some tradeoffs in flexibility).

Hard Water vs. Soft Water: Flora Series and FloraMicro Variants

If you’re in an area with hard water (high calcium and magnesium content), General Hydroponics sells FloraMicro Hard Water, which has adjusted calcium levels to compensate. Standard FloraMicro is designed for soft water.

A quick test: if your tap water EC reading is above 0.4 mS/cm before adding any nutrients, you likely have hard water and should consider the hard water variant or use reverse osmosis filtered water as your base.

Most users start with standard FloraMicro and adjust if they see calcium-related symptoms (tip burn on lettuce, blossom end rot on tomatoes). It’s worth knowing the variant exists.

Pros and Cons

What Works	What Doesn’t
Proven across 40+ years and thousands of grows	No pH buffering — need separate pH management
Flexible ratios work across a wide range of crops	Three bottles to measure (not as simple as one-part)
Very clean — reservoir stays clear	Not organic-certified
Well-documented — problems have been solved before	Hard water version sold separately (check which you need)
Excellent value — $35–45 lasts a long time
Industry-standard — used commercially

Who It’s For

Start with the Flora Series if:

You’re new to hydroponics and want the most proven, well-supported option
You want flexibility to grow a range of crops (herbs, greens, fruiting plants)
You’re running any countertop system (AeroGarden, iDOO, LetPot, or similar) and want to upgrade from starter nutrients
Reservoir cleanliness is important (synthetic = cleaner)
You value having 40 years of community troubleshooting behind your nutrient system

Consider alternatives if:

You want organic inputs (FoxFarm is the better option)
You’re scaling up and want the most cost-effective system per gallon (Masterblend wins)
You genuinely want the simplest possible one-bottle system (accept some flexibility tradeoffs)

The Verdict

The General Hydroponics Flora Series earned its reputation by doing exactly what it’s supposed to do, consistently, across a huge range of crops and growing setups. Forty years of adoption doesn’t happen by accident.

For beginners, it’s the ideal starting point: clear documentation, forgiving ratios, a massive online community for troubleshooting, and a price point that won’t sting. For experienced growers, it remains a reliable baseline to dial in for specific crops.

If you’re running an iDOO, LetPot, AeroGarden, or any countertop hydroponic system and you want to move beyond the included starter nutrients — start here.