How to Grow Brassicas and Wild Rocket Microgreens

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Fill your microgreen tray with compost or your chosen medium to just below the brim of the tray. Spread seeds evenly across the surface, covering as much of the soil as possible so a dense mat of micros will grow. Micros are small so you need to use a lot of seeds to get a good-sized harvest. Avoid covering the seeds with compost.

Give the seeds a thorough misting of water, being careful not to scatter the seeds. Place a second tray on top. This acts as the compost of the top. For the next couple of days, the seeds will need water and darkness to germinate. 

Allow the seeds 3-4 days under blackout to germinate.


Once the germination and blackout period is completed, it’s time to take off the lid and inspect.

We do our utmost at Grown Local to source high-quality seeds, but there is huge variation between batches. Therefore, it is imperative to inspect for any early signs of mould. 

Remember not to confuse root hairs for mould!

  • Mould looks like a fine spider-web, root hairs are fuzzier.
  • Mould is slimy if you touch it but the root airs are not.
  • Root hairs only exist on the root; your mould will grow anywhere on the plant.

Don’t worry if you have mould, the tray may still be salvageable!

 If you only have a small spot of mould remove the infected seed and spray with 3% food-grade hydrogen peroxide.

Continue to keep an eye on the tray and follow up with consecutive sprays of hydrogen peroxide if required.

If the tray has a substantial amount of mould, it is advisable to restart the process but before seeding, prewash your seed with 3% food grade hydrogen peroxide. 

At Grown Local when required we normally leave our seed to soak for 7-10 minutes in the hydrogen peroxide followed by a rinse under clean water.


Always water from the bottom, never from the top, make sure to remove excess water from the reservoir tray after the growing medium has absorbed the maximum amount of water. 

Keeping the roots submerged in water may lead to root rot or pest issues such as gnats.

Keep under lights until the microgreens under lights or on a sunny windowsill into they begin to grow a true leaf.

They should be ready to harvest in 7-14 days.