Growing Spinach Hydroponically: A Tower Garden Growing Guide

Spinach Quick Facts

Spinach doesn't require pollination or additional support, and it doesn't take up a tremendous amount of room in a Tower Garden. The challenge is giving it the cool conditions it prefers and getting good germination from the seed.

How to Germinate Spinach Seeds

For spinach, we normally plant 3–5 seeds per rockwool cube. That's more than we use for many of our other crops because spinach germination can be unpredictable.

We also store our spinach seeds in the refrigerator in an airtight container. We've found that properly stored, refrigerated seed gives us much better germination than we typically see from spinach seed stored at room temperature.

That doesn't mean every seed will germinate, which is one reason we don't rely on planting just one seed in each cube.

Keep the rockwool evenly moist during germination without leaving it sitting in standing water. Temperature matters here too—trying to germinate spinach in very warm conditions can make an already finicky seed even more difficult.

Once you have healthy seedlings with roots beginning to emerge from the rockwool, they're ready to move into the Tower Garden or another hydroponic system.

For seed-starting recommendations for other crops, see our guide to how many seeds to plant.

Where Should Spinach Go in a Tower Garden?

Spinach is relatively easy to place because it doesn't require a cage or trellis and doesn't become as large as crops such as Swiss chard, tomatoes or cucumbers.

Give the plants enough room for the leaves to develop without being shaded by larger neighboring crops. When planning a mixed Tower Garden, remember to think about the eventual size of everything around the spinach rather than the size of the plants when they're first planted.

Spinach also works well for indoor growing, where you have much more control over temperature and light than you do outdoors.

Light and Temperature for Spinach

Growing Spinach Outdoors

Spinach is a cool-season crop. This is one crop where we would not describe the plant as heat tolerant based on our experience growing in the Florida Keys.

When temperatures rise, spinach becomes increasingly difficult to grow well. Warm conditions can stress the plant and shorten the productive growing period, so growers in hot climates should treat spinach as a seasonal crop rather than trying to force it through summer.

This is very different from crops such as Swiss chard, which we successfully grow here throughout the summer.

Growing Spinach Indoors

Indoor growing can make spinach much easier in warm climates because you have greater control over the growing environment.

When using Tower Garden LED grow lights, provide approximately 14–16 hours of light per day followed by complete darkness overnight.

We generally start the LEDs approximately 6–8 inches above the tops of the plants and adjust the lights as the plants grow.

Remember that indoor lighting can also contribute heat. Good airflow and reasonable room temperatures are especially important for a crop that naturally prefers cooler conditions.

For more information about indoor and outdoor lighting, visit our Tower Garden Light Guide.

Water, pH and Nutrients

Spinach can grow alongside other crops in the same Tower Garden and doesn't require its own special nutrient formula.

For established plants, our standard Tower Garden nutrient rate is 20 mL Mineral Blend A and 20 mL Mineral Blend B per gallon of water.

For young seedlings, we generally begin at approximately half strength: 10 mL of A and 10 mL of B per gallon.

Keep the nutrient solution at approximately pH 5.5–6.5.

Because spinach prefers cooler growing conditions, pay particular attention to the reservoir when outdoor temperatures begin climbing. Warm nutrient solution can add another source of stress to a crop that's already unhappy in hot weather.

For more information about managing your system, visit our Tower Garden Nutrients Guide and Tower Garden Water Guide.

Common Spinach Growing Problems

Spinach isn't necessarily difficult once it's established in the right environment. Many of the problems growers experience come back to two things: germination and temperature.

Spinach Seeds Aren't Germinating

Don't assume you're doing something terribly wrong if spinach germination is inconsistent. It can simply be a finicky seed.

Start with good-quality seed, avoid overly warm germination conditions and keep the rockwool consistently moist without soaking it. We also use 3–5 seeds per cube and keep our spinach seed refrigerated in an airtight container.

Spinach Struggling in Warm Weather

If the plants were doing well and begin declining as temperatures rise, heat may be the problem rather than nutrients or something wrong with the Tower Garden.

Spinach simply isn't one of the crops we expect to perform through our Florida Keys summer. In hot climates, switching to a more heat-tolerant leafy green can make more sense than trying to keep spinach productive through unfavorable conditions.

Yellowing or Unhealthy Leaves

If temperatures are appropriate but the plant still looks unhealthy, check nutrient strength, pH, water quality, light and root health.

Pests

Check the leaves regularly, including the undersides, for insects or signs of feeding damage. Catching a pest problem early is much easier than dealing with one after it spreads throughout a densely planted tower.

If you're trying to identify an insect, disease or other plant problem, visit our Pests & Diseases Guide.

How to Harvest Spinach

You don't need to pull the entire spinach plant when you're ready to eat it.

We harvest spinach by cutting the larger outer leaves while leaving the center of the plant intact. The center continues producing new growth, allowing you to return for additional harvests.

Take the larger leaves as you need them rather than allowing older leaves to remain on the plant indefinitely. Be careful not to damage the central growing point when cutting.

Is Spinach Good for Hydroponic Growing?

Yes—but spinach is a good example of why choosing the right crop for your growing conditions matters.

It doesn't need pollination, doesn't need additional plant support and works well in a Tower Garden or other hydroponic or aeroponic system. But it prefers cooler conditions, and germination can require a little more patience than many other leafy greens.

If you're growing indoors in a temperature-controlled environment, spinach can be a particularly useful crop. Outdoors, your location and season become much more important.

Here in the Florida Keys, we grow spinach when conditions are suitable rather than trying to force it through our hottest months. During the summer, we have other leafy greens—such as Swiss chard—that are much better suited to the heat.

Want to compare your options? Visit our Hydroponic Crop Library to explore more leafy greens, herbs, fruiting crops and vegetables for hydroponic growing.

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