Can I grow spinach indoors year-round?
Written by
Benjamin Miller
Reviewed by
Prof. Charles Hartman, Ph.D.In order to successfully grow your spinach plants indoors, you'll need to recreate what they would experience outdoors in their ideal environment. I have been growing them successfully indoors all year with 6500K LED panels that are about 12 inches from the plants. I also have a timer set to provide 14 hours of light daily: this will reduce the chances of your plants becoming leggy. Placing an oscillating fan is also a nice touch to help strengthen the plants' stems, and to provide airflow through the plants with a temperature around 60 - 65°F.
Lighting Requirements
- 6500K spectrum for vegetative growth
- 30-40 watts per square foot
- Adjust height as plants grow
- Use reflective mylar walls
Hydroponic Setup
- pH 6.0-6.5 for nutrient uptake
- EC 1.8-2.2 mS/cm
- NFT or deep water culture
- Weekly reservoir changes
Variety Selection
- Baby leaf types: 20-day harvest cycles
- ‘Space' hybrid for compact growth
- ‘Tyee' for slow bolting
- Avoid savoy varieties indoors
Indoor growing in soil can utilize 5-gallon fabric pots with a peat-free mix. A client of mine had a soil mix made of 60% coco coir, 30% perlite, and 10% worm castings and had up to 8 harvests per year for 5 different crops. Bottom-watering on a tray prevents fungal problems. After watering, simply let the pots sit for 20 minutes and then drain completely.
Having pest control indoors requires vigilance. Put hypoaspis mites into the soil system for the control of fungus gnats. For hydroponics, add 1 tsp of hydrogen peroxide per gallon of water once a week. I eliminated thrips using sticky traps and weekly neem sprays. Test on one leaf before spraying and wait a week to ensure it is not phytotoxic.
You can harvest the microgreens (the young leaves) at 10 days or the mature leaves at 25 days. Sterilize the scissors so you can try a technique called cut-and-come-again; using this technique, I harvested 300g weekly from a 2x4ft shelf. To lengthen their fridge life to 2 weeks, always rinse the leaves in a combination of iced lemon water (1 Tbsp/gal).
Energy efficiency is important. LED panel lighting costs $15 per month for a space with 16 feet by 16 feet, or 256 square feet, footprint. In 2023, I trialed to compare to T5 fluorescents and based on my best estimates saved approx $82 per/year and saw peanut plant increased yield (25%). Use smart plugs to energize and display lighting schedules, capacities, etc. along with the energy monitors to maintain patterns.
Read the full article: How to Grow Spinach: 7 Essential Steps for Success
