General Hydroponics Flora Series Feeding Schedule: The Feed Chart and the Lucas Formula
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General Hydroponics Flora Series Feeding Schedule: The Feed Chart and the Lucas Formula
The General Hydroponics Flora Series is one of the most popular and proven nutrient systems ever made, and for good reason: three affordable bottles, mixed in different ratios as your plant grows, cover a plant from seedling to harvest. But two things trip growers up. First, the official feed chart looks fiddly, with different numbers every week and a long list of optional add-ons that General Hydroponics, like every nutrient company, would love to sell you. Second, there is a famous shortcut, the Lucas Formula, that many growers swear by but few explain clearly. As a shop that stocks the whole Flora line, we would rather keep it simple and honest than sell you a shelf of extras. This guide gives you the complete Flora Series feeding schedule stage by stage, the single mixing rule that actually matters, an honest take on which add-ons are worth it, and the Lucas Formula laid out plainly. You can shop the line on our General Hydroponics page. We don't upsell.
The 30-Second Answer
- The Flora Series is three bottles: FloraGro (vegetative growth), FloraMicro (the base, used the whole grow), and FloraBloom (flowering). You mix them in shifting ratios: Gro-heavy in veg, Bloom-heavy in flower, with Micro steady throughout.
- The one rule that matters: always mix in this order into your water: FloraMicro first, then FloraGro, then FloraBloom. Out of order, the nutrients can precipitate and lock out.
- Dose to EC, not to fixed numbers: aim for roughly EC 0.9 to 1.1 in early veg, rising to 1.4 to 1.7 in flower, then tapering for a flush. Reduce by 25 to 50 percent in soil.
- Or use the Lucas Formula: skip FloraGro entirely and run 8 mL FloraMicro plus 16 mL FloraBloom per gallon for the whole grow. Simple, cheap, and great with RO water.
The three bottles do everything most growers need. We stock the whole line and the add-ons, and we will still tell you to keep it simple. We don't upsell.
The Flora Series: three bottles, three jobs
The whole system rests on understanding what each of the three bottles does, because once you know that, the ratios make intuitive sense. FloraMicro is the foundation of the program and is used during every stage, from seedling through harvest; it supplies nitrogen, potassium, calcium, and the chelated micronutrients that keep everything else available to the plant. FloraGro is the vegetative-growth component, rich in nitrogen and potassium, which builds strong roots, stems, and leafy structure, so it features heavily during veg. FloraBloom is the flowering component, supplying the phosphorus, potassium, magnesium, and sulfur that support bud and flower development, so it dominates during bloom. The genius of the system is that you are not locked into a single formula: you simply adjust the ratio of these three bottles to match what the plant needs at each stage, running more FloraGro when the plant is building green growth and more FloraBloom when it is making flowers, with FloraMicro holding steady as the base underneath. This modular approach is why the Flora Series has remained a favorite for decades and works across so many plants and growing styles. You can run it as a simple base program or dial it in as precisely as you like, which our nutrient buyer's guide discusses alongside other brands.
The one rule that matters: mixing order
If you remember nothing else from this guide, remember this: you must add the three parts to your water in the correct order, which is FloraMicro first, then FloraGro, then FloraBloom, stirring between each. This is not a preference or a superstition; it is chemistry. If you add FloraBloom, which is high in phosphorus, directly to concentrated FloraMicro, which contains calcium, before they are both diluted in water, the calcium and phosphorus can bind together and precipitate out of solution, forming a solid that your plants cannot absorb, which both wastes nutrients and can cause deficiencies. Adding FloraMicro to the water first ensures the calcium is well diluted before the phosphorus arrives, preventing that reaction. For the same reason, you must never mix the concentrated bottles together directly, and you should never pre-mix a batch of full-strength nutrient solution to store for later, since the same precipitation can occur over time; always mix fresh into water. Follow the order every single time, dilute properly, and mix fresh, and you will avoid the single most common and most preventable Flora Series mistake. It takes only a few extra seconds and it protects the entire feed.
The Flora Series feeding chart, stage by stage
Here is the schedule in table form, matching the chart above, in milliliters per gallon. The pattern to notice is that FloraGro leads during veg and FloraBloom takes over during flower, while FloraMicro stays relatively steady as the base. This mirrors the plant's real biology, since research confirms cannabis has a higher nitrogen requirement during vegetative growth and then shifts toward phosphorus and potassium during flowering.
| Stage | FloraMicro | FloraGro | FloraBloom | Target EC |
|---|---|---|---|---|
| Seedling / early | 2 mL/gal | 2 mL/gal | 2 mL/gal | 0.4 to 0.5 |
| Vegetative | 5 mL/gal | 5 mL/gal | 3 mL/gal | 1.4 to 1.7 |
| Transition (early bloom) | 5 mL/gal | 5 mL/gal | 6 mL/gal | 1.4 to 1.7 |
| Bloom (mid to late) | 5 mL/gal | 4 mL/gal | 7 mL/gal | 1.4 to 1.7 |
| Late / ripen | 3 mL/gal | 3 mL/gal | 4 mL/gal | 0.9 to 1.1 |
| Flush (final 1-2 weeks) | Plain pH-balanced water | 0.4 or lower | ||
Treat these as a well-tested starting framework rather than exact commandments, since your ideal numbers depend on your water, medium, and plants. The EC column is the more important guide: if your target EC is met at lower doses because your tap water already carries dissolved minerals, use less. Keep your pH between about 5.5 and 6.5, and in a recirculating reservoir, change the solution every seven to ten days to prevent salt buildup.
The Lucas Formula: the simpler way
For growers who find the shifting three-part ratios tedious, there is a beloved shortcut called the Lucas Formula that simplifies the Flora Series down to just two bottles. The idea, developed by a grower named Lucas, is that FloraMicro already contains enough nitrogen and minerals that FloraGro becomes redundant, so you skip FloraGro entirely and run only FloraMicro and FloraBloom. The classic ratio is 8 mL of FloraMicro plus 16 mL of FloraBloom per gallon of water, a one-to-two ratio, used at the same strength throughout the entire grow, both vegetative and flowering, with no changes as the plant matures. That is the whole method: mix those two amounts into every gallon, and feed. Some growers run a lighter version during veg, such as 5 mL FloraMicro and 10 mL FloraBloom per gallon, then move to the full 8 and 16 in flower, but the appeal of the standard formula is that it never changes. The Lucas Formula was originally designed for reverse osmosis water, with which it tends to self-balance to a good pH, and it is especially popular in hydroponic and deep water culture systems for its simplicity and consistency. If you use tap water, you will need to monitor and adjust pH more actively. It is a genuinely excellent, low-effort way to run the Flora Series, and it saves you from buying FloraGro at all.
How to read and adjust the doses
The most important habit with any feed chart is to dose to your EC or PPM target rather than blindly following the milliliter numbers, because your starting water varies. If your tap water already reads a certain EC, you will hit the target with less nutrient than a grower using pure RO water, so measure your solution and adjust. Beyond that, a few adjustments matter. Start on the lower end and build up, since overfeeding causes the burnt leaf tips of nutrient burn far more readily than underfeeding causes deficiency, a balance our nutrient burn guide covers. Crucially, the standard Flora chart is calibrated for hydroponic and soilless growing, so if you are growing in soil, reduce the doses by roughly 25 to 50 percent to avoid overfeeding, since soil holds and supplies some nutrition of its own. Keep your pH in the correct range for your medium, which our pH guide lays out, and in recirculating systems change your reservoir every seven to ten days. Watch the plant as your final guide: lush, healthy new growth means you have it right, while burnt tips mean back off and pale, hungry leaves mean you can give a little more.
Which Flora add-ons are actually worth it
Here is where an honest shop saves you money. General Hydroponics, like every nutrient company, sells a long list of supplements alongside the three base bottles, and it is easy to feel you need all of them. You do not. The three-part Flora Series is a complete nutrient program on its own and will grow excellent plants with big yields without a single add-on. That said, a few extras genuinely earn their place for some growers. CaliMagic, a calcium-magnesium supplement, is worth having if you use reverse osmosis or soft water, or grow in coco coir, since those situations often need extra cal-mag. RapidStart can give a real boost to early root development. And Liquid KoolBloom, added in the final couple of weeks of flower, is a respected bloom-and-ripening booster that some growers value for a final push. Beyond those three, the rest of the lineup, the various bioactive blends and specialty additives, is genuinely optional, and most growers will not notice a meaningful difference from them. So if you want to add anything, reach for CaliMagic if your water calls for it, RapidStart for roots, and Liquid KoolBloom at the finish, and feel free to ignore the rest. We stock all of it, and we will still tell you the three bottles do the job. We don't upsell.
Flora Series by growing medium
How you run the Flora Series shifts a little with your medium. In hydroponics and deep water culture, the Flora Series is right at home, since it was designed for soilless growing; you can run the full chart rates or the Lucas Formula, keep your reservoir well maintained, and monitor EC and pH closely, since there is no buffer to catch mistakes. In coco coir, which behaves much like hydroponics but can hold onto calcium and magnesium, you feed a full nutrient solution regularly and will very likely want to add CaliMagic, since coco commonly creates cal-mag demand. In soil, the important adjustment is to cut the doses, using roughly half to three-quarters of the hydroponic chart rates, because soil holds nutrients and supplies some of its own, so full hydro rates will overfeed and burn your plants; feed less often, too, letting the soil dry appropriately between waterings. Our guide to soil versus coco versus hydro explains these differences in depth. The core schedule and the mixing order stay the same across all three; you are mainly adjusting concentration and frequency to fit how forgiving your medium is.
Flora Series versus other three-part systems
The Flora Series is far from the only three-part nutrient system, and it is worth understanding where it sits. Its great strengths are affordability, availability, flexibility, and a decades-long track record, which make it a superb choice for beginners and budget-conscious growers as well as experienced ones who value control. Advanced Nutrients offers its own popular three-part and pH-buffered systems with more hand-holding and a larger booster ecosystem, at a higher price, while Athena's professional line takes a lean, dial-to-EC approach favored by commercial growers. None of these is simply better than the others; they suit different priorities and budgets, a comparison we lay out honestly in our General Hydroponics versus Advanced Nutrients guide. What the Flora Series does exceptionally well is deliver proven, flexible, complete nutrition at a very reasonable cost, with the bonus of the Lucas Formula shortcut for those who want maximum simplicity. If you want a trusted base system that adapts to your plants and your wallet, it is hard to beat, which is why it remains a staple on grow-shop shelves worldwide, including ours.
Common Flora Series mistakes
A handful of mistakes cause most Flora Series problems, and avoiding them keeps your grow smooth. The biggest and most preventable is mixing the parts in the wrong order or mixing the concentrates together, which causes nutrients to precipitate and lock out; always go FloraMicro, then FloraGro, then FloraBloom, into water. The second is using the full hydroponic chart rates in soil, which overfeeds and burns plants; cut the doses by a quarter to a half for soil. The third is buying the entire add-on lineup under the impression it is necessary, when the three base bottles do the job. The fourth is following the milliliter numbers blindly instead of dosing to an EC or PPM target, which leads to feeding too strong when your water already carries minerals. The fifth is neglecting pH, since even a perfect nutrient mix is useless if the pH locks nutrients out. And the sixth is forgetting to flush with plain water in the final one to two weeks. Avoid these by mixing in order, adjusting for your medium, keeping your lineup simple, dosing to EC, watching pH, and flushing at the end. We don't upsell, and steering clear of these six is worth more than any supplement.
What We'd Tell You at the Counter
If you brought the Flora Trio to the counter looking a little unsure, we would tell you it is genuinely one of the easiest, most forgiving systems to run, and you need far less than the shelf of add-ons suggests. Get FloraGro, FloraMicro, and FloraBloom, and remember the one rule: always mix them into your water in that order, Micro first, then Gro, then Bloom, never the concentrates together. In veg, lean on FloraGro; in flower, lean on FloraBloom; keep FloraMicro steady the whole time. Dose to your EC, start on the light side, and if you are in soil, use about half the hydro numbers. If all of that still sounds like too much fuss, run the Lucas Formula instead: 8 mL FloraMicro and 16 mL FloraBloom per gallon, the same the whole grow, and skip FloraGro entirely, which is our go-to suggestion for hydro growers on RO water. Add CaliMagic if your water needs it, RapidStart for roots, and KoolBloom at the finish, and ignore the rest. We sell every bottle GH makes, and we will still tell you the three bases do everything. We don't upsell.
Shop the Flora Series
Here is the whole system as a shopping list, so you can grab the trio and only the extras you actually need.
Frequently asked questions
What is the General Hydroponics Flora Series?
The Flora Series is a three-part liquid nutrient system from General Hydroponics, designed for hydroponic and soilless growing but usable in soil at reduced strength. It consists of three bottles: FloraMicro, the foundation of the system, used the whole grow, supplying nitrogen, calcium, potassium, and chelated micronutrients; FloraGro, the vegetative component, rich in nitrogen and potassium for roots, stems, and leaves; and FloraBloom, the flowering component, supplying phosphorus, potassium, magnesium, and sulfur for buds and flowers. You mix the three in different ratios depending on your plant's stage, using more FloraGro in vegetative growth and more FloraBloom in flowering, with FloraMicro steady throughout. It is one of the most popular nutrient systems ever made because it is affordable, widely available, flexible, and proven, and it can be run as a simple base program or dialed in precisely. The three bottles form a complete program on their own.
What order do you mix FloraGro, FloraMicro, and FloraBloom?
Always mix them into your water in this order: FloraMicro first, then FloraGro, then FloraBloom, stirring between each addition. This order is essential, not optional, because of chemistry. FloraMicro contains calcium and FloraBloom is high in phosphorus, and if these two are combined while still concentrated, before being diluted in water, the calcium and phosphorus can bind and precipitate out of solution into a solid your plants cannot use, wasting nutrients and potentially causing deficiencies. Adding FloraMicro to the water first ensures it is well diluted before the phosphorus-rich FloraBloom arrives, preventing the reaction. For the same reason, you should never mix the concentrated bottles directly together, and you should never pre-mix a batch of full-strength solution to store, since precipitation can occur over time; always mix fresh into water. Getting this order right every time prevents the single most common Flora Series mistake, and it costs only a few seconds.
What is the Lucas Formula?
The Lucas Formula is a popular simplification of the Flora Series that uses only two of the three bottles, FloraMicro and FloraBloom, skipping FloraGro entirely. Its creator reasoned that FloraMicro already provides enough nitrogen and minerals that FloraGro is unnecessary. The standard ratio is 8 mL of FloraMicro plus 16 mL of FloraBloom per gallon of water, a one-to-two ratio, run at the same strength throughout the entire grow, both veg and flower, with no changes as the plant matures. That consistency is the whole appeal: you mix the same two amounts into every gallon and feed. Some growers run a lighter version in veg, such as 5 mL FloraMicro and 10 mL FloraBloom per gallon, before moving to the full 8 and 16 in flower. The formula was designed for reverse osmosis water, with which it tends to self-balance pH nicely, and it is especially popular in hydroponics and deep water culture. It is a simple, cheap, effective way to run the Flora Series.
How much Flora Series do I use per gallon?
At typical full strength, a common approach is roughly 2 mL of each part per gallon for seedlings, then around 5 mL FloraMicro, 5 mL FloraGro, and 3 mL FloraBloom per gallon during vegetative growth, shifting to about 5 mL FloraMicro, 4 mL FloraGro, and 7 mL FloraBloom per gallon during flowering, tapering down in the final weeks before a plain-water flush. However, the more reliable guide is to dose to a target EC rather than fixed milliliters, aiming for roughly EC 0.9 to 1.1 in early veg, up to 1.4 to 1.7 in peak growth and flower, then down to 0.9 to 1.1 as you taper. This matters because your starting water varies, so if your tap water already carries dissolved minerals, you will reach the target EC with less nutrient. Start on the lower end and build up, since overfeeding causes nutrient burn more readily than underfeeding causes deficiency, and reduce these amounts by 25 to 50 percent if you are growing in soil rather than hydroponics.
Do I need the Flora Series add-ons?
No. The three-part Flora Series is a complete nutrient program on its own and will grow excellent, high-yielding plants without any supplements. General Hydroponics, like every nutrient company, sells a long list of add-ons, but most growers do not need them. That said, a few genuinely earn their place for some situations: CaliMagic, a calcium-magnesium supplement, is worth adding if you use reverse osmosis or soft water or grow in coco coir, since those often create cal-mag demand; RapidStart can meaningfully boost early root development; and Liquid KoolBloom, used in the final couple of weeks of flowering, is a respected bloom and ripening booster. Beyond those three, the rest of the lineup is optional, and most growers will not notice a significant difference. So keep your kit simple: run the three base bottles, add CaliMagic if your water calls for it, consider RapidStart for roots and KoolBloom at the finish, and feel free to skip everything else.
Can I use the Flora Series in soil?
Yes, but you must reduce the doses. The standard Flora Series feed chart is calibrated for hydroponic and soilless growing, where the medium holds no nutrients of its own, so using those full rates in soil will overfeed and burn your plants, because soil already holds and supplies some nutrition. The fix is to cut the chart amounts by roughly 25 to 50 percent for soil, and to feed less frequently, letting the soil dry appropriately between waterings rather than feeding every time. The mixing order and the general stage pattern stay the same: FloraMicro first, then FloraGro, then FloraBloom, with more FloraGro in veg and more FloraBloom in flower. Watch your plants closely, since burnt leaf tips signal you are still feeding too strong for your soil and should cut back further. Many soil growers also feed plain water between nutrient feedings. With the doses reduced appropriately, the Flora Series works perfectly well in soil.
Flora Series versus Advanced Nutrients: which is better?
Neither is simply better; they suit different priorities. The General Hydroponics Flora Series is affordable, widely available, flexible, and proven over decades, making it an excellent choice for beginners, budget-conscious growers, and experienced growers who value control and the option of the simple Lucas Formula. Advanced Nutrients offers its own three-part and pH-buffered systems with more hand-holding, pH Perfect technology that reduces the need to adjust pH manually, and a larger ecosystem of boosters, but at a noticeably higher price. If your priorities are value, flexibility, and a trusted base system, the Flora Series is hard to beat. If you want maximum convenience and do not mind paying more, Advanced Nutrients has appeal. Both will grow great plants when used correctly, so the honest answer comes down to your budget and how much simplicity versus hand-holding you want. We carry both and are glad to talk through which fits your setup, and we compare them directly in our dedicated guide.
Whether you run the full three-part chart or the simple Lucas Formula, the FloraGro, FloraMicro, and FloraBloom trio plus any extras you actually need live on our General Hydroponics collection, with the alternatives in our premium nutrients range if you want to compare. Keep it simple, mix in order, dose to your EC, and pair this with our guides to how GH compares to Advanced Nutrients, avoiding nutrient burn, pH for cannabis, and the full week-by-week grow guide. Because, as always, we don't upsell.
For informational and educational purposes only. This article is general horticultural guidance and is not legal advice, nor is it affiliated with or endorsed by General Hydroponics. Product names are trademarks of their respective owners. Cannabis cultivation laws vary by country, state and locality, and growing cannabis may be illegal where you live. Always understand and comply with the laws and regulations that apply to you, and follow the manufacturer's official instructions when mixing nutrients, before growing any cannabis plant.
Related guides: which hydroponic system to run and the hydroponic reservoir workflow guide.