How to Grow Spinach Using Hydroponics

  • Nutrient pH 5.5-6.6
  • EC – 1.8-2.3
  • PPM 1260-1610

Spinach is a cool weather crop that lends itself well to the hydroponic realm only when properly cared for. It does not perform as well in higher temperatures

Hydroponic Spinach Temperatures

  • Maximum Temp 75° Fahrenheit
  • Optimal Day Cycle Temps 65 – 70° Fahrenheit
  • Optimal Night Cycle Temps 60 – 65° Fahrenheit
  • Seed Storage 40 to 70° Farenheit
  • Germination 60 to 75° Farenheit

Cold stratification. 1 to 3 weeks prior to planting some growers will store seeds in the refrigerator. It has the effect of hardening them and leads to a healthier plant.

Prolonged warm temperatures will cause most varieties of spinach to bolt to seed, which basically ruins your crop. Spinach that has bolted is bitter and fit only for the compost pile.

Lowering the temperature a few degrees in the days just before you harvest is a good idea as it will promote sweeter, tastier spinach.

The drawback to this is that growth under the cooler conditions will be a tad slower, but I would rather have tasty spinach than useless bitter leaves.

Seed Starting Spinach

Starting Spinach from seed is the best option in my opinion. Seeds become less viable as they age, germination rates decline incredibly. Be sure to use seed that is packaged for the current growing season.

I generally start my seeds in cell packs with potting soil and vermiculite, but they can also be started in Oasis Cubes. They take 6 to 10 days to germinate and emerge. It is best to wait at least two weeks before transplanting the seeds into the Hydroponic setup

Naturally, you’ll want to take care to remove the soil clinging to the young roots without damaging the delicate root system.

Once the soil has been tapped or washed off the roots, I like to dust them with Mycorrhizae, a beneficial fungus that penetrates the root systems of most plants in nature. They are helpful in providing improved uptake of water and nutrients from the growing media.

This is, of course, optional but it does lead to a healthier more robust, and rapidly maturing plant.

Seed Starting in Cubes

Oasis Cubes and similar products are also suitable for starting Spinach seeds. Oasis Cubes are manufactured from water-absorbent foam, Phenolic foam, also known as Floral Foam. Also known as Oasis Root Cubes, they offer a good starting environment for seedlings and plant cuttings, not as a full growing medium.

  1. Moisten the starter cubes.
  2. Insert the seeds into the cube’s holes. You.ll need roughly 4 – 5 seeds per cube, anticipating that some will not germinate and weaker ones can be weeded out later.
  3. They should be placed on a tray and watered daily with 1/4 strength nutrient solution till the seeds germinate and sprout which should only be a few days. After sprouting use 1/2 strength solution.
  4. Once the seedlings are growing, thin out any extra seedlings leaving only the fittest looking seedlings in each cube. Some of the thinned out plants may be suitable for transplant elsewhere.
    When roots begin to show and seedlings reach 2-3 inches tall, with 3-4 true leaves, Your seedlings are ready to leave the nest and enter into the setup.
  5. Spinach plantings should be staggered – roughly 2 – 3-week intervals in order to ensure a continuous harvest.
Lettuce rafts are another method that works well for many growers. They are economical and relatively easy to put together and maintain. They work well for growing spinach, lettuce and other light leafy vegetables and herbs.

Lighting Requirements of Spinach

12 hours of light daily is optimal for spinach. Fluorescent lighting works great, HID, high-pressure sodium and another lighting will work also but be aware that Spinach will grow, but not thrive in excessive light.

If you are in a position to use direct sunlight for your hydroponic spinach, during the peak summer months you might want to consider providing some sort of partial shade.

Putting blue light on plants enhances chlorophyll production and facilitates vegetative leaf growth which is a good thing when growing Spinach.

Red light and yellow is good for flowering, fruit production, neither of which is desirable in a spinach crop.

If you have the resources, Dual Spectrum Lighting is ideal for hydroponic production.

Adjusting light ratios at various points in a plant’s life cycle, or for different plants can be advantageous. Most lighting purchased for indoor or hydroponic gardening is set at a fixed ratio.

However some newer LED systems are designed for maximum plant productivity, they allow for control of each color individually. Red, Blue, Green, Far Red, ultraviolet are all adjustable with the proper system.

Related: Growing Hydroponic Cucumbers

Nutrients for Spnach Grown Hydroponically

Once you’ve perpetrated your transplant – No fertilizer is needed for the first week.

After that, young Spinach plants should be started with 1/4 strength hydroponic nutrients for about 2 weeks. Elevated levels of Calcium and Magnesium are beneficial. Spinach is somewhat nitrogen sensitive and easily gets leaf tip burn when nitrogen levels are too high. You’ll need nitrogen, but not in excess.

After two weeks increase the nutrient to 3/4 strength for a week and then full strength the following week.

Spinach should grow to the point where it is almost ready to develop flower stalks, This is when they should be harvested. At this stage, many fruits and vegetables generally need an abundance of hydroponic nutrients. 

There are exceptions to every rule As spinach approaches maturity, reduce the nutrient strength to ensure the leaves have no bitter taste.