How to Grow Hydroponic Kale: The Guide to Growing Kale Hydroponically

Kale and other green Leafy vegetables are among the easiest crops to grow hydroponically.

Kale will thrive and produce rapidly and abundantly in almost any setup and doe’s not require overly meticulous care.

The health benefits of kale are well documented and undisputed, the culinary attributes are limitless. Unfortunately, fresh kale is not always readily available and when it is, it is frequently chock full of pesticides, fungicides, and commercial chemical hocus pocus.

Organic kale is not impossible to find – but it’s not easy either. Growing your own kale is not all that bothersome.

Kale lends itself well to a hydroponic garden. Kale can be started from seeds or cuttings known as plant starts. If starting from cuttings it is best to reap cuttings from mature plants.

Quick Reference

  • Light: 6 – 10 hours Daily
  • Nutrient pH -5.5-6.5
  • EC 0.8-1.2
  • PPM 560-840

Getting Started Seed or Cuttings

Starting from seed is the best choice in my opinion. In conventional gardening, kale is generally started from seed in the summer or late spring, in a controlled hydroponic environment you can start on Christmas day or the fourth of July – whatever floats your boat.

Germinating Kale Seeds Prior to Moving to Hydroponic System

Kale Seeds germinates best at temperatures between 60 and 75 degrees, they will germinate at lower temperatures, as low as 40 F – but much slower and with a lower germination success rate. They will also germinate at higher temperatures – ditto for germination success rates..

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 prefer to start my kale seeds in cell packs with potting soil and vermiculite, but they can also be started in Oasis Cubes. They take 4 to 7 days to germinate and emerge.

Once they have emerged give them another 4 – 5 days of growth as embryonic plants in the womb of the potting soil, before placing them in your hydroponic system.

Naturally you’ll want to take care to remove the soil clinging to the young roots without compromising the structural integrity of the root system. Once the soil has been delicately tapped off the little root ball, I like to dust the roots with Mycorrhizae, a beneficial fungus which 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 healthier more robust and rapidly maturing kale plant.

Seed Starting in Cubes

Oasis Cubes and similar products are also suitable for starting Kale seeds. Oasis Cubes are manufactured from water-absorbent foam, Phenolic foam, also known as Floral Foam.

Oasis Root Cubes, they offer a good starting environment for seedlings and plant cuttings, not as a full growing medium.


  1. Soak the starter cubes briefly in nonchlorinated water.
  2. Insert the seeds into the cube’s holes. You’ll need roughly 3 -4 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 the extra seedlings leaving only one of the fittest looking seedlings in each cube. Some of the thinned out Kale plants may be suitable for transplant elsewhere.
  5. 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.
  6. Kale plantings should be staggered -roughly 3 – 4-week intervals in order to ensure a continuous harvest.

Maintenance and Basic Requirements of Kale.

Hydroponic Kale Spacing

Try to keep your kale plants spaced at least a foot and a half apart, as they grow you may need to expand this distance in order to allow their broad leaves room to breathe and expand without hampering the progress of one another.

Best Temperature for Hydroponic Kale

The ideal temperature for kale is between 40 to 65 degrees F. during the daylight cycle and slightly lower during the night cycle.

The flavor of kale is known to improve with a very light frost, one trick I’ve used successfully is chilling my plants for a few hours daily for a few days, just before harvesting.

Don’t let the temperature go below 30 – 35 F – you don’t want to freeze them.


In nature, Kale requires full sunlight, a hydroponic system is not much different. A wee bit of shade can’t hurt either. Kale will grow with simple fluorescent lighting.

It would of course grow much better with the more costly lighting designed specifically for hydroponics – such as HID and some of the new LED lights. Whatever lighting you choose, be sure to leave adequate overhead space between the light source and the plant so as to avoid leaf burn.

See – Hydroponic Lighting.

Hydroponic Kale Nutrient Formula

The Nutrients pH should be between 5.5 and 6.5

Some leafy vegetables, which include kale is nitrogen sensitive and easily get leaf tip burn when nitrogen levels are too high. You’ll need nitrogen, but not in excess.

Calcium and Magnesium sulfate is great for kale, but unfortunately are not part of the hydroponic nutrient mixes available, so must be added separately to the Hydroponic solution.

Under lower light levels, such as fluorescent lighting, potassium and nitrogen levels should be reduced.

How Long Does it Take to Grow Kale Hydroponically?

You should be able to start harvesting young baby Kale 20 – 30 days after they were placed in the hydroponic system.

Fully mature Kale can take 3 – 4 months. This of course varies depending on the variety and growing conditions.