Hydroponic Kale
Hydroponic gardening, an innovative method of growing plants without soil, has revolutionized the way we cultivate our favorite vegetables, including the nutrient-rich kale. This guide offers an exhaustive look into the world of hydroponically grown kale, and promises to be an indispensable resource for both novice and experienced gardeners alike.
From the initial stages of starting seeds to the final steps of harvesting and storing, this guide covers every aspect necessary for a successful hydroponic kale garden. So whether you’re intrigued by the simplicity of the Wick System, the efficiency of Deep Water Culture, or the advanced Aeroponics, this guide navigates through everything, ensuring kale thrives in whichever setup you choose.
Additionally, it delves into the specifics of growing conditions—like optimal pH levels, seed depth and spacing, and lighting requirements—tailored to kale’s unique needs. This comprehensive guide not only simplifies the technicalities of hydroponic gardening but also encourages sustainable living by enabling readers to grow kale indoors and outdoors, year-round, regardless of climate or space constraints.
Let’s embark on this green journey to mastering the art of hydroponic kale cultivation, ensuring your plates are always filled with fresh, home-grown greens.
Table of Contents:
- Starting Seeds
- Hydroponic Systems
- Growing Conditions
- Transplanting and Growing Maintenance
- Harvesting and Storing
- FAQs
Starting Kale
Starting Kale seeds for hydroponic systems requires a precise approach to ensure a successful and healthy crop, but isn’t any more difficult than starting seeds in a soil-based garden.
Seed Considerations
When selecting seeds for hydroponic Kale, opt for high-quality, disease-resistant varieties. Ensure the seeds are fresh, as older seeds may have lower germination rates, crucial for a successful hydroponic setup. Remember that the fundamentals behind seeds don’t change; anything that can germinate in soil will generally follow the same pattern in hydroponics as you’re typically just replacing soil with a hydroponics growing medium.
Starting Seeds Indoors
To start Kale, plant your seeds in a suitable hydroponic growing medium (such as coco coir pith), about ¼-½ inch (0.6 – 1.3 cm) deep. This should be done 5-6 weeks before the last expected frost if you intend to transfer your kale outdoors. Keep the temperature around 65-70°F (18.3 – 21°C) for optimal germination, which typically occurs in about 4 to 7 days. After sprouting, ensure your new kale plant receives sufficient light for healthy growth. Remember to keep the growing medium consistently moist.
Starting Seeds Outdoors
Direct sowing kale seeds in your outdoor hydroponic system is best done 4 to 5 weeks before the last expected frost. Ensure your growing medium and the nutrient solution in the reservoir have warmed to at least 45°F (7.22°C); then, plant seeds ¼-½ inch (0.6 – 1.3 cm) deep and 8-12 inches (20.3 – 30.5 cm) apart to accommodate the mature plant size.
Hydroponic Systems for Kale
There are six basic types of hydroponic systems, Wick, DWC, Ebb and Flow, NFT, Drip, and Aeroponics, each offering unique advantages for cultivating plants. Kale, in particular, will thrive in any one of them, making it a versatile choice for hydroponics.
The Wick System
Ideal for beginners, wick systems provide a low-maintenance environment for kale, using capillary action to deliver water and nutrients directly to the roots. This setup minimizes root disturbance and maintains consistent moisture levels, supporting steady growth without the need for complex equipment or monitoring. Learn more about Wick Systems here.
Deep Water Culture (DWC)
In DWC systems, kale roots are suspended in nutrient-rich water, promoting rapid growth and lush leaves. Using a pump and air stone, this method ensures high oxygen levels at the roots, and is largely considered a hands-off system. However, it does require careful monitoring of water temperature and nutrient concentration. Learn more about Deep Water Culture here.
Ebb and Flow (Flood and Drain)
Ebb and Flow systems periodically flood the root zone with nutrient solution and then drain it away, offering kale an optimal balance of water, nutrients, and air. This ‘on/off’ cycle encourages strong root development but demands precise timing and control to prevent root rot or drying out. Learn more about Ebb and Flow Systems here.
Nutrient Film Technique (NFT)
NFT systems constantly flow a thin layer of nutrient solution over kale roots, ensuring they receive a continuous supply of water and nutrients while exposed to air. This balance promotes fast, healthy growth, but requires consistent monitoring to avoid blockages in the flow channels. Learn more about NFT Systems here.
Drip System
Drip systems provide a targeted and controlled delivery of nutrient solution to kale through drip irrigation tubes, allowing for efficient water and nutrient use. This method supports uniform growth and is adaptable to various plant sizes, but requires regular system checks to prevent clogging and ensure even distribution. Learn more about Drip Systems here.
Aeroponics
Aeroponics offers the most advanced and efficient environment for kale, misting the roots with nutrient solution in a highly oxygenated chamber. This method encourages rapid, robust growth and minimal root disease, but demands precise control of misting intervals and nutrient strength. Learn more about Aeroponic Systems here.
The Kratky Method (Honorable Mention)
The Kratky method is a simple, non-circulating, passive hydroponic technique where plants grow directly in a nutrient-rich solution. Kale can do quite well in this low-maintenance setup, making it an ideal choice for those new to hydroponics or gardeners with limited space. Learn more about the Kratky System here.
Growing Conditions for Hydroponic Kale
Kale, when grown hydroponically, requires specific conditions to thrive. For the best results, it’s essential to carefully manage various factors such as pH levels, seed depth and spacing, germination time and optimal germination temperature, time to maturity, lighting needs, and preferred reservoir temperature.
pH
Kale Prefers a pH range of 5.5 – 6.5 in hydroponic systems. Regularly monitoring and adjusting the pH is crucial, as the correct pH balance ensures nutrient availability and optimal plant health.
EC
Maintain your nutrient solution’s EC between 1.2-2.2 to ensure your kale receives the right concentration of nutrients. Too low of an EC and the plants may show deficiency symptoms, too high and you risk nutrient burn.
Seed Depth and Spacing
Plant your kale seeds about ¼-½ inch (0.6 – 1.3 cm) deep. If directly sowing outside, space your kale seeds about 8-12 inches (20.3-30.5 cm) apart when planting. Proper spacing is vital for adequate air circulation and light penetration, promoting healthy growth and preventing disease.
Germination Time and Germination Temperature
Kale seeds typically germinate around 4 to 7 days when maintained at an optimal temperature of 65-70°F (18.3 – 21°C). Consistent warmth during this stage is key to prompt and uniform sprouting. Kale is unlikely to germinate at all if temperatures are below 40°F (7.2°C) or above 85°F (29.4°C).
Time to Maturity
Kale is typically ready to harvest in 55-80 days in outdoor conditions. However, in hydroponic systems under optimal conditions (think indoors, perfect lighting, optimal reservoir temperature, good nutrient levels, etc.), it may be significantly quicker. Keep a close eye as the harvest time approaches to enjoy the freshest, most flavorful leaves.
Light Requirements
Kale prefers 6 to 8 hours of direct sunlight a day, but needs a minimum of 4 to 6 hours a day. If growing indoors under grow lights, ensure that your kale receives between 12 and 16 hours of light to mimic natural conditions. High-quality, full-spectrum grow lights can ensure your plants receive the necessary light energy for robust growth.
Growing Temperature (Air)
Kale grows best in cooler air temperatures between 60°F to 70°F (15.5°C to 21.1°C) but can tolerate frost and cold temperatures down to about 20°F (-6.6°C). Maintaining this range will encourage healthy growth and prevents bolting or stunted growth.
Preferred Reservoir Temperature
For most plants, the ideal, “optimal” nutrient solution temperature in hydroponic systems is generally between 68-72°F (20°C to 22.2°C), though some growers may extend this range slightly to 68-75°F (20-24°C). The term “optimal” signifies the most favorable conditions, but slight variations outside this range are typically not a concern. For kale, however, because it’s such a cool-weather crop, you’ll likely find more success between 60°F to 70°F (15°C to 21°C). Also note that temperatures above 80°F (27°C) or below 60°F (16°C) will likely lead to poor growth and potential root diseases.
Recommended Hydroponic System
Kale will do well in a almost every system, however, it’s important to consider that kale plants can grow rather tall. To ensure there’s enough space for the plant, it may be best to start with Ebb and Flow, Drip, or DWC. These systems typically provide the space that kale needs to thrive.
USDA Plant Hardiness Zone
While your local USDA zone is irrelevant if growing inside (under controlled conditions), if growing outside, your hardiness zones for kale include 2a, 2b, 3a, 3b, 4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b, 9a, 9b, 10a, 10b, 11a, 11b. Important Note: USDA Zones only apply to USA Growers.
Transplanting and Growing Kale Hydroponically
Hydroponic growing can be pretty hands-off, but it doesn’t entirely eliminate the need for maintenance. Much like traditional gardening, you still need to regularly check and maintain your Kale throughout the growing process.
Transplanting
If you started your kale seeds indoors, you can usually transplant them into your hydroponic system within 5-6 weeks. Handle them gently to avoid root damage and ensure the roots make good contact with the nutrient solution in their new system. It’s best to transplant when seedlings are sturdy and have a few true leaves, signaling they’re ready for more vigorous growth.
Growing Mediums
The growing medium you use is entirely dependent on your hydroponic system. It also can come down to personal preference (what’s worked for you, what’s available, etc.). To learn more, read up on hydroponic systems and hydroponic growing mediums to pick the right one. Ultimately, the medium you choose should facilitate nutrient flow and root development while also providing stability to your growing kale plants.
Reservoir Maintenance
Regularly check and adjust your nutrient solution’s pH and EC levels to ensure your kale receives the ideal balance of nutrients. Change the solution every 2-3 weeks to prevent nutrient imbalances and build-up of harmful substances.
Preventing Algae
Limit light exposure to the nutrient solution and keep your hydroponic system clean to prevent algae growth. Covering reservoirs with light-blocking materials, using opaque (non-transparent) containers, and maintaining a clean environment are effective strategies against algae.
Pruning
Prune any yellowing or dead leaves to maintain airflow and plant health. Regular pruning also helps direct the plant’s energy towards producing large, healthy leaves.
Pollination
When growing kale for leaf harvest, pollination is not needed, as leaves are picked before flowering; however, for seed saving or enhancing genetic diversity, allowing flowering and ensuring insect pollination is key.
Disease Prevention
Keep your hydroponic system clean and monitor plants regularly for signs of disease (such as leaf spot and black rot). Quick identification and isolation of affected plants, along with proper air circulation and nutrient management, are key to preventing the spread of disease.
Plant Support
As kale grows, it may become top-heavy in your hydroponic system. If you find your plant falling over at the base, provide support with stakes or nets to ensure the plants remain upright.
Pest Management
Regardless of whether you’re growing inside or outside, pests can and do make their way to your plants. It’s important that you regularly inspect your plants for signs of pests and maintain a clean growing area to prevent infestations. If pests are detected, use appropriate, hydroponic-safe control methods such as insecticidal soaps or natural predators. Some of the more common kale pests include aphids, cabbage worms, cabbage loopers, flea beetles, slugs, and caterpillars.
Harvesting and Storing Kale
Harvesting and storing kale properly ensures you enjoy the freshest taste and maximum nutrients from your hydroponic garden.
What will your kale look like when it’s ready?
A fully mature kale plant typically reaches 8 inches to 1 foot 2 inches (20.32 to 35.56 cm) in height and 1 to 1.5 feet (30.48 to 45.72 cm) in width, varying with the variety and growing conditions.
When to Harvest
Kale is typically harvested between 55 and 80 days (although perfect hydroponic conditions may speed this up considerably). Harvest when several leaves have developed, are about 5 to 8 inches in length, and look crisp, dark, and firm in appearance.
How to Harvest
Harvest in the morning for optimal freshness. Lower leaves can be harvested as early as 30 days after planting for raw consumption in salads. As the plant grows, harvest mature lower leaves when they reach five to eight inches in length, as smaller leaves tend to be more tender. Additionally, the entire plant can be harvested if desired.
Storing Kale
After harvesting your kale, store in a in a loosely closed plastic bag to keep the leaves crisp and prevent yellowing. Kale can be stored in the refrigerator (between 32-40°F (0-4.4°C) for up to two weeks; for longer storage, consider blanching and freezing it to maintain quality and nutritional value (should last you around 8-12 months but will be less nutritious).
FAQs
Can I just top off my nutrient solution in my hydroponic system?
It’s recommended that you change the nutrient solution in your reservoir out every 2-3 weeks. However, for everyday hobbyists, this really depends on personal preference how serious you want to take the hobby. If you’re growing for someone else, it may be best to “go by the book” and fully change it out. If you’re growing for yourself, the choice is really yours. Many hobbyists do just fine by topping off the water/nutrients when it gets low and then cleaning out the system after a few grows.
Is it ok to use plastic to grow Kale?
Yes, it is perfectly safe as long as you’re following Food Grade Safe standards.
Does kale grow well in containers?
There are many hydroponic systems that use containers and kale will do well in any one of them. For more information, read up on our container size standards for vegetables guide.
Are Nutrient Deficiencies Common?
Hydroponics is truly a trial and error hobby and if you’re just starting out, you’re probably going to have some nutrient issues. Make sure to continually monitor your plants and look for any abnormalities. If anything looks off, do some ‘plant deficiency research’ and adjust as needed.
Are kale roots large?
Kale roots are small to medium in size/length and will do well in most hydroponic systems (aka size shouldn’t be a problem). If you’d like to learn more, you can read up on vegetable root sizes here.
Where can I find more information on hydroponics?
If you’d like to learn more about hydroponics, give our Hydroponics Hobby Center a read. The Hydroponics Hobby Center contains system guides, plant guides, charts, etc. that will help you get started.