How to Grow Arugula Microgreens

Arugula microgreens grow indoors year-round, so there is no season to wait for and no USDA zone to worry about. Aim for a comfortable room temperature of about 65 to 75 degrees Fahrenheit and set the tray on a bright windowsill or under a grow light once the seeds have sprouted. Because arugula matures in only about a week and a half and does not regrow after cutting, keep a few trays going on rotation, starting a fresh one every week or so, for a steady supply of peppery microgreens.

Arugula grows best as tray microgreens, and the key rule is do not soak the seed. Arugula seed is mucilaginous and forms a gel when wet, which makes jar sprouting messy, so sow it dry straight onto the tray.

Tray method: Use a shallow tray no more than about 2 inches deep and fill it with an inch or two of moistened fine seed-starting mix or coconut coir. Scatter the dry seed densely and evenly across the surface with minimal overlap, then mist lightly, the seeds will form a harmless clear gel as they take up moisture. Cover the tray or set it under a blackout dome for about 2 to 4 days to hold moisture and encourage even sprouting, keeping the surface moist but not soggy. Once the seeds have sprouted and pushed up, uncover the tray and move it into bright light.

Why not a jar: because arugula gels when wet, jar sprouting is slimy and hard to rinse. The tray method gives you clean, full, peppery microgreens with far less fuss.

After germination, switch to bottom-watering: add water to the tray beneath rather than over the top so the foliage stays dry, which is the single best defense against mold. Give the greens 10 to 16 hours of bright light a day and keep the air moving with good ventilation. Keep the medium consistently moist but never soggy, hold the room around 65 to 75 degrees Fahrenheit, and keep your trays and tools clean. Arugula grows fast and rarely has pest trouble indoors, so clean, airy, evenly moist conditions are almost all it needs.

Arugula microgreens are ready in about 8 to 12 days, once the cotyledon leaves have fully opened (the first true leaves may just be showing) and the greens stand about 1.5 to 2 inches tall. Harvest by cutting the stems just above the soil line with clean, sharp scissors. Let them dry a little, then store them dry in an airtight container in the refrigerator and wash only right before use. Microgreens do not regrow after cutting, so start a fresh tray for your next crop.

Arugula microgreens deliver a bold peppery, nutty flavor, an intense version of mature arugula, so a little goes a long way. Pile them on salads, sandwiches, wraps, and grain bowls, scatter them over pizza and pasta right before serving, or use them as a sharp garnish for eggs and soups. Beyond flavor, they are prized for nutrition: microgreens are remarkably nutrient-dense, often more concentrated in vitamins and antioxidants than the mature plant.

• Mold vs. root hairs: fine white fuzz hugging the stem near the seed that vanishes when misted is normal root hair. Slimy or cobweb-like growth spreading across the soil with a sour smell is mold. Fix mold with more airflow, less water, and thinner sowing.
• Seed gel looks strange but is normal: arugula seed forms a clear jelly-like coating when moist. It is harmless and helps hold moisture, do not rinse it off.
• Damping off: seedlings collapse at the base from fungus in soggy, stagnant conditions. Bottom-water, improve ventilation, and avoid overwatering.
• Leggy, pale greens: too little light. Move the tray to a brighter windowsill or under a grow light and give 10 to 16 hours a day.
• Uneven or patchy germination: usually uneven sowing or uneven moisture. Spread the dry seed evenly and keep the whole surface consistently damp during blackout.