As I mentioned in my Hydroponics Guide to pH and EC, getting the pH and EC right can make the difference between plants that merely survive and ones that absolutely thrive in your hydroponic garden.
In this guide, I’ll elaborate on why different plants need different pH and EC ranges!
And, I’ve put together easy-to-read charts so you can dial in your nutrient solution perfectly for herbs, leafy greens, and fruiting vegetables.
Why Do Different Plants Need Different pH and EC Ranges?
Think of pH and EC as the keys that unlock your plants’ ability to absorb nutrients:
pH controls nutrient availability
Nutrient availability shifts with pH.
Certain nutrients dissolve more easily (and are easier for plants to absorb) at specific pH levels.
For example, iron and manganese are more available in slightly acidic conditions, while calcium and magnesium are easier to take up closer to neutral pH.
A nutrient that’s easy to absorb at pH 6.0 might be harder to access at pH 7.0.
Read more: Hydroponic Nutrients 101
Plants evolved in different environments
Herbs, leafy greens, and fruiting vegetables all come from unique native soils and climates.
As a result, they naturally prefer different nutrient profiles and pH levels.
For example, herbs like basil or parsley come from regions with slightly acidic soils, so they’re naturally adapted to absorb nutrients best at pH 5.5–6.5.
Fruiting crops like tomatoes, on the other hand, are more tolerant of a wider pH range.
They often benefit from a slightly higher pH to optimize calcium and magnesium uptake, which is important for fruit development.
Root sensitivity matters
Some plants have sensitive roots that need a stable, narrower pH range to efficiently take up nutrients without stress.
Leafy greens especially have finer, more sensitive roots.
They’re more easily affected by pH swings and need a narrower window of pH to stay healthy.
How to Test pH and EC
You can test pH using an inexpensive test kit like this one. If your solution is too acidic or basic, use pH up or down to adjust.
EC can be easily tested using a meter.
I like this one – it’s small and unobtrusive, works with virtually any brand of countertop indoor gardens and is accurate yet affordable.
By fine-tuning both pH and EC, you help your plants take up the right nutrients at the right time.
This gives them what they need for strong growth, vibrant leaves, and tasty harvests.
Ideal pH and EC Chart for Hydroponic Plants
Herbs
| Plant | pH | Ideal EC (mS/cm) |
|---|---|---|
| Basil | 5.5 – 6.5 | 1.0 – 1.6 |
| Chives | 6.0 – 7.0 | 1.0 – 1.8 |
| Cilantro | 6.5 – 7.5 | 0.8 – 1.2 |
| Dill | 5.5 – 6.5 | 1.0 – 1.8 |
| Lavender | 6.5 – 7.5 | 1.2 – 1.8 |
| Lemon Balm | 5.5 – 6.5 | 1.0 – 1.6 |
| Mint | 6.0 – 7.0 | 1.6 – 2.2 |
| Oregano | 6.0 – 7.0 | 1.0 – 1.8 |
| Parsley | 5.5 – 6.0 | 0.8 – 1.8 |
| Rosemary | 6.0 – 7.5 | 1.4 – 2.0 |
| Sage | 6.0 – 7.5 | 1.4 – 2.2 |
| Thyme | 6.0 – 7.0 | 1.0 – 1.8 |
| Watercress | 6.0 – 7.0 | 1.0 – 2.0 |
Vegetables
| Plant | pH | Ideal EC (mS/cm) |
|---|---|---|
| Bok Choy | 6.0 – 7.5 | 1.5 – 2.5 |
| Broccoli | 6.0 – 6.8 | 2.8 – 3.5 |
| Cabbage | 6.5 – 7.0 | 2.5 – 3.5 |
| Cauliflower | 6.5 – 7.0 | 0.5 – 2.0 |
| Carrots | 6.3 – 6.8 | 1.6 – 2.4 |
| Celery | 6.3 – 6.7 | 1.8 – 2.4 |
| Leeks | 6.5 – 7.0 | 1.4 – 1.8 |
| Lettuce | 5.5 – 6.5 | 1.2 – 2.0 |
| Kale | 5.5 – 6.5 | 1.8 – 2.3 |
| Radish | 6.0 – 7.0 | 1.6 – 2.2 |
| Spinach | 6.0 – 7.0 | 1.8 – 2.3 |
| Swiss Chard | 6.0 – 7.0 | 1.8 – 2.5 |
| Tatsoi | 6.0 – 7.0 | 1.5 – 2.5 |
Fruiting Plants
| Plant | pH | Ideal EC (mS/cm) |
|---|---|---|
| Beans | 6.0 – 7.0 | 1.4 – 2.4 |
| Blueberries | 4.0 – 5.0 | 1.8 – 2.0 |
| Cucumbers | 5.5 – 6.0 | 1.7 – 2.5 |
| Edible Flowers | 5.5 – 6.5 | 1.0 – 2.0 |
| Eggplant | 5.5 – 6.5 | 2.5 – 3.5 |
| Melons | 5.5 – 6.5 | 2.0 – 3.5 |
| Peas | 6.0 – 7.5 | 0.8 – 1.8 |
| Peppers, Bell | 5.8 – 6.8 | 2.0 – 3.5 |
| Peppers, Hot | 5.5 – 6.5 | 2.0 – 3.5 |
| Tomatoes | 5.8 – 6.8 | 2.0 – 3.5 |
| Squash | 5.5 – 6.8 | 1.8 – 2.4 |
| Strawberries | 5.5 – 6.5 | 1.0 – 1.5 |
| Watermelon | 5.8 – 6.2 | 1.5 – 2.4 |
| Zucchini | 5.5 – 6.5 | 1.8 – 2.4 |
How to Use the Charts
- Group plants with similar ranges together in the same indoor garden.
- Certain vegetables may want different nutrient strengths depending on where they are in their growing cycle. The ranges above are a general guideline, and you should research your specific crop and growing cycle to fine tune.
- Seedlings and young plants need gentler nutrient solutions because their roots are still developing. Start low and gradually increase EC as the plants mature.
- Test pH and EC regularly (2–3 times a week) to make sure you’re staying within target ranges. I recommend measuring at the time of mixing, as well as after it’s had time to become available to your plants.
- EC values will fluctuate, so it’s helpful to measure EC every single day using a continuous meter like this one. By doing so, you’ll be able to spot and fix issues much more quickly.
- It’s a good habit to completely empty your reservoir and supply fresh nutrient solution every 7-10 days.
Note:
These charts are designed specifically for hydroponic growing, where plants get nutrients directly from water. Hydroponic plant roots are much more sensitive to changes.
In soil, plants benefit from buffering by organic matter and soil particles, so they tolerate slightly wider ranges of pH and nutrient strength.
EC typically isn’t measured for soil gardening.
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