Best Temperature for DWC Hydroponics (Tips on Control)

In a system like deep water culture, where roots are placed in water for a long time, maintaining a healthy temperature is vital. In fact, aside from the hydroponic system itself, a thermometer is one of my first investments in gardening, and here’s why.

Generally, plants can tolerate 65 to 80°F nutrient solution temperature in deep water culture (DWC) hydroponics. To control this, a gardener can 1) grow in a controlled set up 2) paint the reservoir white, 3) keep the plants off the ground, 4) put ice packs, 5) add cold water, 6) invest in ventilation, and 7) use grow tents.

At this point, you may be wondering: Is the temperature requirement of lettuce similar to that of tomatoes? How can I control the temperature if I am from a place with a hot climate? What should I do during cold seasons? Let me equip you with answers in this article.

Does Temperature in Deep Water Culture Matter?

Yes, temperature matters. Studies revealed that temperature significantly affects the metabolism and nutrient uptake of plants.

Considering this, they can change the plant’s composition such as nutrition factors and active phytochemicals. For instance, it was found that hydroponic lettuce cultivated in a cold environment gained 20% more dry matter content compared to those produced in warm places.

This is the reason why there is a need to control the temperature when growing in deep water culture hydroponics.

Temperature Range for Common Hydroponic Veggies and Herbs
Temperature Range for Common Hydroponic Veggies and Herbs – Infographic

10 Plants & the Best Temperatures in DWC Hydroponics (Full List)

To help you further, here is a list of different veggies and herbs along with their respective ideal temperatures for growth in a deep water culture (DWC) hydroponic setup.

PlantsNutrient Solution Temperature Range (°F)
Lettuce45-70
Spinach64-70
Kale59-77
Basil59-77
Chives64-70
Watercress77-86
Strawberries55-70
Tomatoes71-78
Peppers73-78
Cucumbers71-75
Best Temperatures for Common Hydroponic Veggies and Herbs

At this point, I believe that you already noticed that each plant requires and tolerates a certain temperature range. Some veggies and herbs love hotter climates while some, like lettuce, are fit for cooler climate areas.

But how does cold or hot temperature affect our plants? Let us move forward!

Effects of Hot and Cold Temperatures on DWC Hydroponics

Too hot or too cold nutrient water temperatures are detrimental for the plants. Heat promotes microbial proliferation; whereas coldness slows growth.

A hot solution will cause the proliferation of bad bacteria and an increase of microorganisms. This will be bad for the plant roots as it can trigger root rot disease.

Conversely, the plants will develop slower at lower temperatures. The coldness will shut down the functioning of the roots. When this happens, they will not be able to get enough oxygen.

Effect of Cold Temperature on Plant Growth
Effect of Cold Temperature on Plant Growth

7 Ways to Control Temperature

Both surrounding and water temperature are important to control in deep water culture hydroponics. Thus, one of the best practices a gardener does is to place thermometers around the growing area.

Remember that the surrounding temperature also affects the water temperature. Thus, this practice will surely help you monitor if you are giving your veggies and herbs the right temperature they need.

10 Tips to Lower the Temperature of your Hydroponic Reservoir

1. Grow Indoors or in a Greenhouse

Growing in a controlled environment, such as indoor spaces and greenhouses, is the best way to control and manipulate external and nutrient water temperature in hydroponics.

One of the interesting questions I encountered in my hydroponic journey is: What if I do not have access to cooler or hotter temperatures and I want to grow a plant like strawberries?

I always answer that the best solution for that is indoor growing or growing in a greenhouse where you can have full control over the temperatures and other climate factors.

2. Paint Your Reservoir White

White color reflects light. Thus, coating the reservoir with white paint can prevent the increase of nutrient water temperature.

White-coated reservoirs do not absorb the heat along with light.

Ever wondered why polystyrene or styrofoam boxes are used as deep water culture hydroponic systems? This is the reason why! Using them takes advantage of their color and their physical property as an insulator.

This makes a cheap and effective choice for hydroponics gardening.

3. Keep the Plants Off the Floor

For people with cooler climates, plants must be placed above a platform such as tables or shelves. This is because cold air sinks and can further slow the growth of plants.

This is an applicable step during the winter season or if you are someone who lives in a cold location.

Remember that cold air is heavier and therefore, sinks. Considering this, it is best to keep items such as water and plants off the ground. Plants will thrive better on a table.

4. Put Ice Packs into the Nutrient Water

Adding one ice pack every 15 minutes is a simple and attainable way to control nutrient water temperature.

If you are a hydroponic gardener in a hot climate area, keeping 10-15 ice packs on hand and adding one to your reservoir every 15 minutes is a wise option.

With every ice pack added, remember to check the water temperature and stop when it is already within the acceptable range based on your plant’s specific needs and requirements.

However, this tip is only applicable to household and small-scale gardens. Why? Because this approach may become time-consuming, thereby not feasible, for bigger gardens.

5. Add Cold Water

If ice packs would be costly, adding cold water can also control nutrient solution temperature.

However, if you do this, keep in mind that every time you add water, the nutrient solution will be diluted. Therefore, always check the electric conductivity and adjust when appropriate.

6. Invest in Ventilation

Cooler and extractor fans are wise investments to control for temperature, especially in large-scale gardens.

If you are someone who owns a grow room, you can invest in a ventilation system. Using an inline extractor fan, hot air can be led out of your indoor garden. Because hot air rises, your extractor fan should be placed at the top of your room.

Furthermore, the flow of cooler air can be ensured by providing your plants with ventilation through an electric fan.

7. Use Grow Tents

Grow tents are foldable tents used to grow veggies and herbs indoors. Using them allows a gardener to fully manipulate the environmental conditions the plants are exposed to.

Through this investment, you will be able to create your desired garden ecosystem distinct from the rest of your indoor area. You can now regulate the light, water, temperature, and humidity your plants are getting—allowing them to grow healthier.

You can set this up in areas that are not usually used as gardens such as a garage or a closet.

FAQs

What is the healthy temperature for the roots?

Temperatures in the root zone should be maintained between 68°F and 70°F. Generally, both the root zone and nutrient water should be kept in this operational range. This will provide the nutrition solution with balanced heat and coldness to encourage strong growth rates while retaining adequate oxygen levels.

When should I change my DWC hydroponic water?

Changing the water in deep water culture must be done in 1 to 2-week intervals because your plants consume nutrients and water daily. Learn more about this in our article how often should I change my hydroponics water.

Summary of Best Temperature for DWC Hydroponics

In general, the hydroponic water temperature must be kept between 65 and 80°F, depending on the plant. Leafy vegetables such as lettuce can tolerate colder temperatures, while fruiting vegetables like tomatoes can tolerate hotter environments.

Hot nutrient water temperatures lead to the reproduction of bad bacteria that can cause root rot. Whereas, unsuitably cold temperatures slow down the metabolism of plants as it blocks root activity.

In order to control the temperature, a gardener can 1) grow indoors or in a greenhouse, 2) paint the reservoir white, 3) put the plants on high platforms, 4) add ice packs, 5) add cold water, 6) invest in ventilation, and 7) invest in grow tents.

Sources

  • “Effect of temperature on the composition of hydroponic lettuce” by Gent, M.P.N. in Acta Horticulturae
  • “Heating requirements for winter hydroponic lettuce production” by Miller, A. et al. in Purdue University Extension
  • “Nutrient Solution Temperature Affects Growth and ◦Brix Parameters of Seventeen Lettuce Cultivars Grown in an NFT Hydroponic System” by Thakulla D. et al. in Horticulturae

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