Ideal PPM for Cannabis: Nutrient Levels by Stage
Quick answer: On the common 500 (US) scale, the ideal PPM for cannabis rises with the plant: roughly 100-300 for seedlings and clones, 300-600 in early veg, 600-900 in late veg, 900-1100 in early flower and 1100-1400 at peak flower, then a plain-water flush at the end. PPM measures nutrient concentration, so start low, raise it as the plant grows, and let the plant’s response fine-tune it. Note there are two PPM scales (500 and 700), so always use the one your meter reports.
PPM (parts per million) tells you how concentrated your nutrient solution is, essentially how much food is dissolved in the water your cannabis drinks. Get it right and the plant takes up nutrients efficiently; get it wrong and you risk nutrient burn (too high) or deficiencies and slow growth (too low). Because the plant’s appetite changes through its life, the ideal PPM is a moving target that rises from seedling to peak flower, then drops for the final flush.
Recommended Strains
24K Gold Regular
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THC | 19% - 22% (Medium) |
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Type | Regular |
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Yield | High |
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Phenotype | 60% Indica / 40% Sativa |
Acapulco Gold
|
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THC | 15% - 19% (Medium) |
|
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Type | Feminized |
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Yield | High |
|
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Phenotype | 30% Indica / 70% Sativa |
This guide gives the ideal PPM ranges by stage, how to measure and adjust them, and how PPM relates to EC. The chart below is your quick reference. One important note up front: there are two PPM scales (the 500/US and 700/EU scales), and the same solution reads differently on each, so always check which scale your meter uses before following any chart.
| Stage | PPM (500 scale) |
|---|---|
| Seedlings / clones | 100-300 |
| Early vegetative | 300-600 |
| Late vegetative | 600-900 |
| Early flowering | 900-1100 |
| Peak flowering | 1100-1400 |
| Late flush | 0-400 (plain water) |
Ideal PPM Levels by Growth Stage
Seedlings and fresh clones are delicate and want a very weak solution, around 100-300 ppm (500 scale), as their small roots burn easily. Through vegetative growth you steadily raise it: roughly 300-600 in early veg and 600-900 as the plant bulks up, feeding the heavy leaf and stem growth of this stage. These are guidelines, heavy feeders take the top of each range, light feeders and autoflowers the bottom.
In flowering, demand peaks: about 900-1100 ppm in early bloom and up to 1100-1400 at peak flower, before you drop to plain water (near 0) for the final flush to clean out salts. Watch the plant, burnt, clawed tips mean the PPM is too high, so dilute; pale, slow growth with correct pH can mean it is too low. These numbers are a framework, not a rule.
Promos & Deals
How to Measure and Adjust PPM
Measure PPM with a cheap TDS/PPM meter: dip it in your mixed nutrient solution to read the input PPM, and test the run-off too, run-off much higher than input means salts are building up in the medium and you should flush. To raise PPM, add more nutrients; to lower it, dilute with plain (pH-corrected) water. Always adjust pH after changing nutrient strength, as the two interact.
Because PPM is just a conversion of EC, many growers prefer to read EC directly to avoid the 500-vs-700 scale confusion. Whichever you use, stay consistent. For the EC and pH side of the same equation, see our guide on the best EC and pH for nutrient uptake, and to plan feeds over the season, the outdoor nutrient schedule.
PPM by Medium: Soil, Coco and Hydro
The growing medium changes how you apply these numbers. In hydroponics the roots feed directly from the solution, so PPM targets are followed closely and watched carefully, with little buffer for error. Coco behaves similarly to hydro and is fed regularly to target PPM. Soil, especially rich organic soil, buffers nutrients and supplies some itself, so you generally run at the lower end of the ranges, or feed less often, to avoid overfeeding.
So treat the chart as a hydro/coco baseline and dial it down for soil. Whatever the medium, the plant is the final judge: healthy green growth means your PPM is about right, while burn or deficiency tells you to adjust. Keeping input and run-off readings in check across the week is the simplest way to stay in the ideal range.
Troubleshooting PPM Problems
If your plants look unhappy, PPM is a good first thing to check. Signs the PPM is too high include burnt, brown leaf tips, clawing or curling leaves, and dark, overly green foliage, the fix is to dilute the solution, flush the medium with plain pH-corrected water if salts have built up, and feed lighter. Checking run-off PPM against your input PPM reveals salt accumulation: run-off much higher than input means the medium is loading up with excess nutrients.
Signs the PPM is too low include pale, yellowing leaves and slow, weak growth, but only after you have ruled out pH lockout, which mimics deficiency even when nutrients are present. Always confirm pH is in range before adding more food. Adjust in small steps, re-measure, and give the plant a day or two to respond rather than overcorrecting, PPM management is about steady fine-tuning, not big swings.
FAQs
What is the ideal PPM for cannabis?
On the 500 scale, roughly 100-300 ppm for seedlings, 300-600 early veg, 600-900 late veg, 900-1100 early flower and 1100-1400 at peak flower, then plain water for the flush. PPM rises as the plant grows. Start low, adjust to the plant’s response, and use the scale your meter reports (500 or 700).
What PPM for the vegetative stage?
Around 300-600 ppm (500 scale) in early vegetative growth, rising to 600-900 in late veg as the plant bulks up. Heavy feeders take the top of the range; light feeders and autoflowers the bottom. Start lower and raise it as growth demands, watching for burnt tips (too high) or pale growth (too low).
Is PPM the same as EC?
They measure the same thing, nutrient concentration, on different scales. PPM is a conversion of EC, and there are two PPM scales (500 and 700) that give different numbers for the same solution. Many growers prefer EC because it is unambiguous. Whichever you use, stay consistent and check which scale any chart refers to.
What happens if PPM is too high for cannabis?
Too high a PPM over-concentrates the nutrient solution and causes nutrient burn: brown, crispy leaf tips, clawing leaves and salt build-up in the medium. The fix is to dilute the solution, flush with plain pH-corrected water if salts have accumulated, and feed lighter. Checking run-off PPM against input PPM helps spot the problem early.
