Aeroponics in Cold Climates – GROZINE

Growing Vegetables with Bare Roots in Cold Weather

Growing with aeroponics in cold climates can be surprisingly productive, even when plants are cultivated with bare roots. In fact, bare roots are part of the secret to success when growing in cold weather while keeping power bills to a minimum.

Naturally, there are limits—even when selecting commonly cultivated cold-tolerant vegetable varieties like Swiss chard, kale, broccoli, lettuce, greens, and Brussels sprouts. However, if you can maintain air temperatures above freezing, it’s a pretty good bet you can enjoy success cultivating cold-weather crops using aeroponics.

A greenhouse or cold frame helps significantly by protecting crops from excessively cold temperatures, frost, and snow. That said, you don’t need to rely on energy-intensive heaters to warm the air. Instead, a small-wattage aquarium heater placed in the nutrient reservoir—the solution misted over the bare roots—can be the key to successful, low-power aeroponics in cold climates.

Why Heating the Roots Works Better Than Heating the Air

Key point: Plants are approximately 90% water, and water is an excellent medium for transferring and storing heat—one reason liquid-cooled engines are more common than air-cooled systems.

If the nutrient solution applied to bare roots is maintained at an optimal temperature and delivered with sufficient frequency, the plant itself remains at a more favorable temperature than the surrounding air. After all, the plant is mostly water.

In practical terms, it may take several thousand watts to keep the air inside a small greenhouse at ideal temperatures during cold weather. By comparison, our experience shows that only several hundred watts are needed to maintain an insulated nutrient reservoir at the correct temperature. That heat is delivered directly where it matters most: inside the plant rather than the surrounding air.

The result is a dramatic reduction in energy use without sacrificing plant health or productivity.

Practical Limits of Heating Nutrient Solutions

There are, of course, practical and biological limits when heating nutrient solutions for aeroponics in cold climates. Excessively warm reservoir temperatures reduce dissolved oxygen levels and can lead to undesirable plant responses, such as premature bolting—similar to what occurs in hot climates.

A Healthy Temperature Range for Cold-Weather Aeroponics

Based on our experience, maintaining a nutrient solution temperature between 6°C and 15°C works very well for aeroponic crops such as Swiss chard, broccoli, and kale.

Air temperatures inside our cold-weather greenhouse typically range from 3°C to 15°C, generally providing about a +6°C lift over outside air temperatures. During especially cold periods, we’ve observed reservoir temperatures dip to just above freezing—around 1°C for several hours—with no apparent damage or growth setbacks.

Tips for Success Growing Cold-Weather Crops with Aeroponics

Start Seedlings Indoors

Established cold-tolerant vegetables grow well in cool conditions and often prefer them. However, germination and early seedling development still require warmer, more stable temperatures—typically 65–72°F (18–22°C).

Low-power, full-spectrum LED strip lights work well for starting seedlings and contribute a small amount of supplemental heat. A lighting schedule of 18 hours on / 6 hours off has proven effective when starting plants for aeroponics in cold climates.

Harden Off Before Transplanting

Once seedlings develop a few sets of true leaves and a healthy root system, gradually acclimate them to cooler temperatures before transplanting. Place trays in a cooler environment for an hour or two at a time, slowly increasing exposure. This “hardening off” process helps prevent shock or growth stalls.

Understanding Light Levels in Cold-Season Growing (DLI)

During colder seasons, both daylight hours and light intensity may be significantly reduced. In some regions, supplemental lighting is extremely beneficial; in others, it may be unnecessary.

It helps to understand DLI (Daily Light Integral)—a measure of how much usable light plants receive over a 24-hour period.

In our experience, a DLI of around 15 is sufficient to produce strong, fully mature crops, including broccoli, kale, and Swiss chard. We achieve this with modest supplemental lighting in our cold-weather greenhouse. An added bonus is that LED grow lights contribute a small amount of heat, which is welcome in cold climates.

General DLI Ranges by Geography and Season

Typical Outdoor DLI Values:

• Tropics
  Monthly averages typically range from 20–40 mol·m⁻²·day⁻¹
• Mid-Latitudes (≈30°N)
  Generally range from 15–60 mol·m⁻²·day⁻¹
• Higher Latitudes (≈60°N)
  Can vary widely from 1–40 mol·m⁻²·day⁻¹
• Temperate Regions (Seasonal Variation)
  • Winter: 2–5 mol·m⁻²·day⁻¹
  • Summer: 25–30 mol·m⁻²·day⁻¹

These values help explain why modest supplemental lighting can make such a big difference for aeroponics in cold climates.

Other Water Culture Methods for Cold-Climate Growing

In our experience, other bare-root, recirculating nutrient systems—such as RDWC (recirculating deep water culture), DWC (deep water culture), and NFT (nutrient film technique)—are also well suited to growing vegetables in cold climates using minimal power.

What these systems share is a common advantage: roots grow in a volume of nutrient solution that can be efficiently heated. As with aeroponics, far less energy is required to heat water than to heat air.

We prefer high-pressure aeroponics because it offers greater control over air-to-water ratios in the root zone (rhizosphere), while still allowing frequent nutrient misting from a heated reservoir to maintain optimal root temperatures.

Aeroponics in Cold Climates: Frequently Asked Questions