How Should I Water My Microgreens?

Watering is the aspect of microgreens growing that trips up the most beginners. It seems simple — pour water on plants — but the method, timing and amount all matter significantly. Water incorrectly and your crop will suffer mould, damping off, uneven growth or wilting. Water correctly and your trays almost run themselves. The key insight is that microgreens need to be watered from the bottom, not the top, once they are in the light phase.

Why Bottom Watering Works

Bottom watering means filling a solid-bottomed tray with a small amount of water and setting the growing tray inside it so the medium wicks moisture upward. The key advantage is that the canopy — the stems and leaves of the microgreens — stays completely dry. Wet foliage is the primary driver of mould growth in microgreens. Fungal spores are always present in the air; they need surface moisture on the plant to germinate and colonise. Eliminate wet foliage and you eliminate most mould problems.

Bottom watering also encourages roots to grow downward toward the moisture, which anchors the plants more firmly in the medium and produces sturdier stems. This matters at harvest: well-anchored plants can be cut with scissors without the entire mat lifting up.

How to Bottom-Water

Pour 1 to 2 cm of water into the solid reservoir tray. Set the growing tray inside it and allow the medium to absorb water for 10 to 20 minutes. The medium will darken as moisture wicks upward. Remove the growing tray from the reservoir, allow excess water to drain, and return the growing tray to its usual spot. Empty and dry the reservoir tray to prevent standing water from becoming a habitat for algae or fungus gnats.

How Often to Water

Frequency depends on the growing medium, tray size, ambient temperature and how dense the canopy is. As a starting point: check your trays daily and water when the top centimetre of medium feels dry to the touch. In warm conditions with a dense canopy, this will often be once a day. In cooler conditions or with a sparse seedling tray, every 2 days may be enough. Resist the urge to water on a fixed schedule — learn to read the trays instead.

Overwatered microgreens show wilting, yellowing, and stem softening at the base. Underwatered microgreens show dry, curling leaf edges and the medium pulling away from the tray sides. Both are fixable: allow an overwatered tray to dry out over 24 hours; water an underwatered tray from the bottom immediately.

The Initial Misting Exception

During the first phase — sowing through the blackout germination period — top-misting is appropriate and necessary. Seeds need surface moisture to soften the seed coat and begin germination, and they cannot yet draw water upward because roots have not formed. Mist the surface once or twice during the 3 to 4 day blackout period to keep seeds damp without saturating the medium. Once the cover is removed and the tray moves to light, switch immediately to bottom-watering only.