The complete guide to growing hydroponic lettuce
Seed to salad in about 30 days. Lettuce is the crop hydroponics was practically designed for, and the best possible confidence builder.
Lettuce is fast, shallow-rooted, and undemanding, which is why almost all commercial hydroponic produce is leafy greens. It also gives you visible progress every single day, which matters more than people expect when you are learning.
| Target | Value |
|---|---|
| Time to harvest | 3 to 5 weeks from transplant |
| pH | 5.5 to 6.5, ideally 6.0 |
| EC | 0.8 to 1.2 mS/cm (low, lettuce is a light feeder) |
| Air temperature | 60 to 70F (15 to 21C) |
| Light | 10 to 14 hours per day |
| Spacing | 6 to 8 inches between plants |
Best varieties
- Buttercrunch. The classic hydroponic lettuce. Reliable, tender, and forgiving.
- Black Seeded Simpson. Extremely fast loose-leaf. Often pickable in under three weeks.
- Romaine (Parris Island). Slower but sturdy, and it holds up in a sandwich.
- Salanova and oakleaf mixes. Attractive, and they regrow well after cutting.
- Avoid iceberg. Slow, needs to head up tightly, and much fussier about temperature.
Cut and come again
This is where lettuce earns its place. Rather than pulling the whole plant, cut the outer leaves about an inch above the base with clean scissors and leave the growing centre intact. New leaves push from the middle and you can repeat this two or three times over several weeks from one plant.
Stopping bolt
Other greens on the same settings
Spinach, arugula, bok choy, kale, chard, mizuna and watercress all run happily on the numbers in the table above. Kale and chard simply take a couple of weeks longer and then produce for months.
Need a system to grow it in?
Every plan on this site is free and costs under $50 to build.