Spinacia oleracea
How to grow spinach hydroponically
Cool-loving leafy green that bolts fast in heat. Ideal for cooler rooms and winter indoor grows.
Difficulty
Beginner
Days to harvest
30–40 days
pH range
5.5–6.6
EC range
1.8–2.3 mS/cm
PPM range
900–1150 PPM (500 scale)
Temperature
50–70°F (10–21°C)
Light hours
12–14 hours
PPFD target
200–350 µmol/m²/s
Best systems
Spinach is a cool-season crop — treat it that way
Spinach evolves for cool conditions. Warm air and warm nutrient solution accelerate bolting (flower stalk), bitterness, and quality loss. If your grow room runs hot for basil and tomatoes, spinach will fight you.
Aim for air roughly 50–70°F and cooler solution temperatures. Many growers keep reservoirs under ~68°F for spinach.
Nutrition and growth rate
pH about 5.5–6.6. EC for spinach is often higher than lettuce — commonly cited bands around ~1.8–2.3 mS/cm (roughly 900–1150 PPM on 500 scale), adjusted to cultivar and light.
Moderate PPFD (~200–350 µmol/m²/s) with 12–14 hour days is a sensible indoor starting point. Long photoperiods and heat together encourage bolting.
Systems and harvest
NFT and DWC both work when temperatures cooperate. Dense NFT plantings need good flow and cleaning because spinach cycles can be quick succession crops.
Harvest baby leaf early for salads; full leaves before the stalk elongates. Once bolting starts, flavor and texture decline fast — replant rather than fighting a committed flower stalk.
Troubleshooting
Yellow older leaves: check EC and nitrogen supply. New-growth chlorosis: check pH/iron. Tip burn under strong LEDs: lower intensity or EC and improve airflow.
If plants elongate and taste sharp, assume heat/bolting stress first.
Quick lab tips
• Keep solution under ~68°F to delay bolting.
• Harvest baby leaves early for tender texture.
• Use moderate light — intense PPFD plus heat triggers stress.
Frequently asked questions
Why does my hydroponic spinach bolt?
Usually heat, long stressful days, or cultivar choice. Cool the room/reservoir and harvest earlier.
What EC for hydroponic spinach?
Often higher than lettuce — many programs sit near ~1.8–2.3 mS/cm. Verify with plant response.
Is spinach good for beginners?
Yes if you can keep temperatures cool. In a warm basil room, choose lettuce instead.