Green Kale Microgreen Seed

Kale is one of the cole crops and generally likes moderate to warm temperatures. Kale can produce a crop in as little as six days but usually takes 8 to 10 days.

Microgreen Soil

Like most microgreens, Kale benefits from a well-drained, nutritious soil consisting of:

• Peat or coir for rooting and holding water (75%)
• Perlite or vermiculite for drainage and aeration (20%)
• Small amount of high-quality compost for nutrition (5%)
• Lime to neutralize pH

Many sources state that microgreens do not need nutrients to grow as they have “all the nutrients they need already in the seed”. Our experience is that microgreens grow better with additional soil nutrients, which can be provided with a small amount of compost in your soil mix. Good-quality compost also adds microbial life which can help reduce crop disease. However, too much compost, especially nutrient-rich compost like worm castings, can result in surface mold and reduced water uptake due to nutrient salt content.

Sanitizing Microgreen Seeds

Sanitizing your Kale seed helps reduce the likelihood of human pathogens in your crop. Zerotol is a peracetic-acid-based sanitizer which is approved for organic use in Canada and the United States.

Kale is a small seed and is best sowed when dry. This affects how Kale seed is sanitized.

Kale seed can be sanitized by one of two methods:

1. Immersion then dry (preferred): The seed is sanitized by immersion in sanitizer then dried before sowing. The immersion method ensures the seed is fully engulfed in sanitizer to improve its efficacy. This is an effective but tedious process.
2. Spray after sowing: The seed is sanitized after sowing. This method only exposes one side of the seed to the sanitizer so is less effective than the immersion method.

Sowing Microgreen Seed

Sow Kale seed using the “sprinkle” method where the seeds are sprinkled onto the soil surface. The sprinkling can be done by using a “shaker”, a small handled sieve, or even a small jar or cup - everyone has their preferred method. Important in sowing the seeds is to get good coverage with the sprinkle as the seed cannot easily be redistributed once it is on the soil surface. Make several passes while sprinkling the seed lightly instead of trying to get the distribution perfect in one heavy pass.

Germination

The germination stage can set the crop up for success or failure. Poor germination can be difficult to recover from so optimizing germination conditions is crucial for crop success.

Kale germinates well at room temperature and even a bit below, but germinates even quicker at warmer temperatures. Germinate Kale in the dark.

Stacking Sowed Trays

Kale does well when “stacked” during germination, where trays are stacked one on top of the other.

For stacking Kale shoots:

• Stack trays to a maximum of 3 trays high to prevent toppling. Also reduces pressure on the bottom tray
• Top the stack with an empty tray and 14-lb concrete paver

The top tray will have slightly taller growth than the bottom tray, but come harvest time they will almost completely even out.

Uncovering Kale Microgreens

Kale shoots are best uncovered when they are ½- inch to one inch tall. The thin stems will lodge (fall over) easily if there is too much weight on top as they grow.

Water Kale shoots thoroughly when removing them from the germination stage and moving to the light. The fresh water after three to four days in germination seems to help stimulate growth. Do not get broccoli leaves wet after a first overhead watering.

Lighting

Kale shoots thrive in 14 to 16 hours of light at 5000K to 6500K, or in natural light. If using LED or fluorescent lights, keep them close enough to the crop to prevent stretching. How close will depend on the intensity of your lights.

Online information shows a wide range of optimum PPFD values for microgreens production, ranging from 50 to 400 (Liu et al., 2022; MechaTronix, 2023) We have had success with PPFD values as low as 25.

Watering

Many growers like to water their crops using the “flood” method, allowing the soil to absorb water from below instead of from above. This method keeps the crop dry, which can reduce disease pressure and make for easier harvesting. Place a solid tray below your growing tray and fill that solid tray with water. How much water you add will depend on how dry the crop is and takes some time to master. Do not overwater as waterlogged trays are at higher risk of crop disease.

Harvesting Kale Microgreens

Kale is an easy crop to harvest and process. By keeping Kale leaves dry in the last 24 to 36 hours of growth they can be harvested and placed right into packaging.

Cut Kale shoots close to the base of the stem with a sharp, good-quality knife. Do not use scissors as this will tear the base of the stem and reduce storage time. Kale does not have a firm stem, so be gentle when cutting. Cut small sections at a time with a quick motion with the knife to ensure a good quality cut.

Packaging

For retail locations, growers typically use a clamshell for optimizing both display and storage. For bulk packaging options, you can use roll bags or reusable containers.

Storing Kale Microgreens

Like most microgreens crops, Kale shoots should be kept dry and stored in a fridge between (2° to 4° C or 25° to 39° F) at all times. Be sure to maintain the cold chain during transport by using coolers with ice or a refrigerated vehicle.

Modern Grower Research

At Modern Grower we are constantly doing microgreens trials to better understand crop growth characteristics in varying conditions. All the data we provide is informed by our research.

Check out our ongoing research here to get a better understanding of the crop.