Controlling environmental factors is a huge benefit of hydroponic gardening. The flip side of that, is you need to know what your plant wants so you can help it grow and produce at its peak.
Two important factors in hydroponic gardening are pH & EC levels. A hydroponic solution’s pH refers to its level of acidity or alkalinity. The acidity of a solution affects the availability of specific nutrients for absorption by plants.
Want to learn more about pH?
Check out Understanding & Maintaining pH in Hydroponics.
EC (Electrical Conductivity) is a measurement of dissolved salts in a solution. As a hydroponic gardener, EC measures how strong your hydroponic solution is. Too strong and your plants will burn and ultimately be unable to absorb water and nutrients. Too weak and your plants will struggle to develop due to a lack of nutrients.
The charts and images below are excellent resources to save you time and jump-start your next hydroponic grow.
I've been using this kit for about 8 months and love it. It comes with everything you need to keep the tester calibrated and highly accurate.
Optimal pH & EC for Hydroponic Vegetables
These values will get you safely in the ballpark for growing happy, healthy plants. Your local climate and hydroponic system will play a part in these values as well, so experiment within these ranges to find the optimal combo for your specific growing environment.
Note: Seedlings and young plants will respond best to nutrient solutions on the weaker end of the ranges listed. Slowly increase the strength of the nutrient solution throughout the growth of the plant.
Want perfect lighting?
Check out How to Get Perfect Plant Lighting!
Plant DLI Charts – DLI Calculator – How To Guide
Hyperlinked vegetable names below will take you to full-length hydroponic growing articles. These are super helpful if you want to learn how to grow something new!
| Vegetable | | Optimal pH | | Optimal EC | |
|---|---|---|
| Artichoke | 6.5-7.5 | 0.8-1.8 |
| Arugula | 6.0-7.5 | 0.8-1.2 |
| Asparagus | 6.0-6.8 | 1.4-1.8 |
| Basil | 5.5-6.5 | 1.0-1.6 |
| Bean (Common) | 6.0 | 2.0-4.0 |
| Beatroot | 6.0-6.5 | 0.8-5.0 |
| Bok Choi | 6.0-7.0 | 1.5-2.5 |
| Broad Bean | 6.0-6.5 | 1.8-2.2 |
| Broccoli | 6.0-6.5 | 2.8-3.5 |
| Brussell Sprout | 6.5-7.5 | 2.5-3.0 |
| Cabbage | 6.5-7.0 | 2.5-3.0 |
| Capiscum | 6.0-6.5 | 1.8-2.2 |
| Carrots | 6.3 | 1.6-2.0 |
| Cauliflower | 6.0-7.0 | 0.5-2.0 |
| Celery | 6.5 | 1.8-2.4 |
| Cucumber | 5.5-6.0 | 1.7-2.5 |
| Eggplant | 5.5-6.5 | 2.5-3.5 |
| Endive | 5.5 | 2.0-2.4 |
| Fodder | 6.0 | 1.8-2.0 |
| Garlic | 6.0 | 1.4-1.8 |
| Kale | 5.5-6.5 | 1.2-1.5 |
| Leek | 6.5-7.0 | 1.4-1.8 |
| Lettuce | 5.5-6.5 | 0.8-1.2 |
| Marrow | 6.0 | 1.8-2.4 |
| Okra | 6.5 | 2.0-2.4 |
| Onions | 6.0-6.7 | 1.4-1.8 |
| Pak Choi | 7.0 | 1.5-2.0 |
| Parsnip | 6.0 | 1.4-1.8 |
| Pea | 6.0-7.0 | 0.8-1.8 |
| Pea (Sugar) | 6.0-7.0 | 0.8-1.8 |
| Pepino | 6.0-6.5 | 2.0-5.0 |
| Peppers | 5.8-6.3 | 2.0-3.0 |
| Peppers (Bell) | 6.0-6.5 | 2.0-3.0 |
| Peppers (Hot) | 5.0-6.5 | 3.0-3.5 |
| Potato | 5.0-6.0 | 2.0-2.5 |
| Pumpkin | 5.5-7.5 | 1.8-2.4 |
| Radish | 6.0-7.0 | 1.6-2.2 |
| Spinach | 6.0-7.0 | 1.8-2.3 |
| Silverbeet | 6.0-7.0 | 1.8-2.3 |
| Sweet Corn | 6.0 | 1.6-2.4 |
| Sweet Potato | 5.5-6.0 | 2.0-2.5 |
| Taro | 5.0-5.5 | 2.5-3.0 |
| Tomato | 5.5-6.3 | 1.5-3.0 |
| Turnip | 6.0-6.5 | 1.8-2.4 |
| Zucchini | 6.0 | 1.8-2.4 |
I use this graduated cylinder set all the time for small measurements. They're well-marked and work great for diluting hydrogen peroxide and mixing nutrient solutions.
Optimal pH & EC for Hydroponic Herbs
Like the above list for vegetables, this list will set you on the right track for growing happy hydroponic herbs. Depending on where you live, and the climate of your hydroponic garden, you’ll want to experiment within the listed ranges to find the optimal pH & EC for your plants. Experimenting is part of the fun!
Most herbs perform well in a pH range of 5.5-6.5, and an EC range of 1.0-1.6, but there are exceptions as you’ll see below. If an herb you want to grow isn’t listed, it’s a safe bet that this general range will get the plant started safely.
Note: Seedlings and young plants respond better to the low end of the listed EC ranges. As the plant begins to grow and mature, increase the strength of the nutrient solution towards the higher end of the recommended range.
| Herb | | Optimal pH | | Optimal EC | |
|---|---|---|
| Anise | 5.8-6.4 | 0.9-1.4 |
| Basil | 5.5-6.0 | 1.0-1.6 |
| Catnip | 5.5-6.5 | 1.0-1.6 |
| Chamomile | 5.5-6.5 | 1.0-1.6 |
| Chervil | 5.5-6.0 | 0.8-1.8 |
| Chickory | 5.5-6.0 | 2.0-2.4 |
| Chives | 6.0-6.5 | 1.8-2.4 |
| Cilantro | 5.8-6.4 | 1.2-1.8 |
| Coriander | 5.8-6.4 | 1.2-1.8 |
| Dill | 5.5-6.4 | 1.0-1.6 |
| Fennel | 6.4-6.8 | 1.0-1.4 |
| Lavender | 6.4-6.8 | 1.0-1.4 |
| Lemon Balm | 5.5-6.5 | 1.0-1.6 |
| Mint | 5.5-6.0 | 2.0-2.4 |
| Mustard Cress | 6.0-6.5 | 1.2-2.4 |
| Oregano | 6.0-7.0 | 1.8-2.3 |
| Parsley | 5.5-6.0 | 0.8-1.8 |
| Rosemary | 5.5-6.0 | 1.0-1.6 |
| Sage | 5.5-6.5 | 1.0-1.6 |
| Tarragon | 5.5-6.5 | 1.0-1.8 |
| Thyme | 5.5-7.0 | 0.8-1.6 |
| Watercress | 6.5-6.8 | 0.4-1.8 |
Download the First Grow Cheat Sheet for step-by-step instructions, DIY templates, and shopping lists that will take your first grow to the next level!
Time to Grow
Be sure to bookmark this page, and save the image if you like, for future quick reference! As I come across new plants I’ll keep updating. If you’re looking for something not listed above, let me know and I’ll research and include it.
If you’re new to soilless gardening, hydroponic herbs are a great way to get started! They will grow well in pretty much any hydroponic system and are really easy to care for.
Keep in mind, the levels and ranges listed here are for soilless hydroponic gardening. Now it’s time to get out your pH & TDS meter, and get growing!
Download the First Grow Cheat Sheet for step-by-step instructions, DIY templates, and shopping lists that will take your first grow to the next level!