Arugula microgreens are baby arugula plants that you harvest very young, when they are just a couple of inches tall, for a bold peppery, spicy flavor. They are one of the fastest microgreens to grow: scatter about 10 grams of seed thickly on a damp tray, cover it to keep it dark for a day or two while the seeds sprout, then move it into bright light to green up, and snip in about 6 to 8 days (a bit longer in a cool or dim room). Arugula seed gets sticky when wet, so mist it instead of soaking. You grow them indoors all year on a shallow tray of seed-starting mix or a special growing mat, so there is no outdoor season or weather to worry about, and they grow the same way no matter where you live. Use them fresh on salads, sandwiches, and as a garnish.Arugula microgreens are the young seedlings of arugula (Eruca sativa, in the mustard family), harvested at the cotyledon to first-true-leaf stage for a concentrated, distinctly peppery, spicy bite that is the whole reason to grow them. They are among the fastest microgreens: a dense, even sow of about 10 g per 1020 tray, a short blackout of about 1 to 2 days to even the stand, then 18 hours of light to green up, cut in roughly 6 to 8 days (longer, closer to 10 to 12 days, in cooler or lower-light rooms). The seed is small and mucilaginous, so it is misted rather than presoaked, or it clumps. Grown indoors year-round on a shallow tray of mix or a fiber mat, arugula microgreens need no frost, season, or hardiness zone, so the same tray grows identically on a windowsill anywhere. They are used fresh as a peppery salad base, sandwich layer, or garnish.
Indoors, every week of the year. Most mixes are ready in 7 to 12 days; start a fresh tray every week for a steady supply.
An even, dense scatter of seed across the whole surface with no bare patches and no thick clumps. The mix underneath should look evenly damp and dark, not soggy or pooling.A uniform, dense seed layer with no gaps or clumping on evenly moist medium.
The seeds swell, split, and push out tiny white roots, then pale looped stems that lift the cover slightly. Under the cover everything looks pale and leggy, which is exactly right at this stage.Seeds imbibe and split; white radicles emerge, followed by pale hooked hypocotyls lifting the weighted cover.
A dense mat of pale, stretched stems standing tall and lifting the cover. The stems will be yellowish or white, not green yet, and that is normal in the dark.Uniformly elongated, blanched stems lifting the cover; a tall, even stand pre-greening.
The stems and seed leaves turn from pale to bright green within a day or so. Soon a small, ruffled first true leaf may appear at the center, and the tray starts to smell peppery.Rapid greening of cotyledons; first true leaf may form. Peppery aroma develops.
Open, fully green seed leaves standing about one to two inches tall, sometimes with a tiny true leaf just showing. They should taste bright and peppery.Cotyledons fully expanded and green at 1-2 in, first true leaf just emerging; peppery flavor developed.
The numbers that matter, at a glance.
For arugula microgreens, the tray is the whole setup. Use a shallow tray with drainage holes sitting inside a solid tray so you can water from the bottom. Wash and sanitize trays between batches.The tray is the entire growing system: shallow, drained, nested over a solid tray for bottom-watering, sanitized between cycles. A clean, reused, food-grade tray beats a single-use clamshell for both food safety and consistent results.
Ask what your balcony or roof can carry
A balcony or roof can only hold so much weight. Before you set heavy pots there, ask a building architect what it can safely carry.Illinois Extension's guidance is to consult a building architect about weight limits before placing heavy pots on a balcony or rooftop garden. It gives no weight figure.
Never grow food in a container with anything toxic in it
Many kinds of containers can be used. Whatever you choose, keep anything toxic out of it, especially if you are growing food.Colorado State accepts nearly any container material but warns against using a container that holds toxic materials, especially for edible plants. Illinois adds that a vegetable container should be free of chemicals toxic to plants or people, and urges caution with treated lumber when growing food. If you cannot account for what a repurposed container once held, that alone is a reason to keep food out of it.
Secure hanging containers well
Fasten hanging baskets and window or rail boxes securely. Think about what is below them too, since they can drip on people or things underneath.Illinois Extension asks growers to secure hanging containers well and to think through the safety issues of hanging them. Placement matters too, since a hanging container can drip onto people or belongings below.
You do not need to worry about soil pH for arugula microgreens. The mixes and mats sold for microgreens are already fine as they are.pH is not a practical lever for a single short indoor cycle on a soilless medium; standard seed-starting mixes and coir sit in a workable range and need no adjustment for arugula.
You do not need to feed arugula microgreens. The seed carries enough food to reach harvest, and adding fertilizer just invites algae and odd flavors.Arugula microgreens are cut before they exhaust the seed's own reserves, so no fertilizer is needed for a single cycle on an inert medium or seed-starting mix. Added nutrients mainly raise the risk of algae and off-flavors; a hydroponic grower who wants to feed at all needs only a dilute 50 to 100 ppm nitrogen solution.
Your arugula microgreens are ready when the first little seed-leaves are open and, for many, the first true leaf is just showing, usually about 6 to 8 days after sowing and around 1 to 2 inches tall. Cut them while they are young for the best peppery flavor, before the bigger leaves come in. Snip them just above the soil with clean scissors and eat them fresh. They do not grow back, so you start a new tray each time.Cut at the cotyledon to first-true-leaf stage, typically about 6 to 8 days from sowing (up to roughly 10 to 12 in cooler or lower light), when the stand is a couple of inches tall and bright green. Harvest before the true leaves and stem fiber develop, since that is when the flavor shifts from pleasantly peppery to harsh. Snip just above the medium with clean scissors; the stand will not regrow, so the tray is a single cut.
You measure microgreens by the tray, not by each plant. A full 1020 tray of arugula gives you a few good handfuls, around 5 ounces.Yield is measured per tray, not per plant: a well-sown 1020 tray of arugula returns roughly 5 ounces of cut microgreens (Penn State reports about 148 grams, near a third of a pound, over a two-week cycle).
Each tray gives one harvest at its best. To keep a steady supply, start new trays every few days.Every tray is a single harvest at peak; continuous supply comes from staggered sowings, not from regrowth. There is no waiting period with microgreens. Your very first tray works just like the rest; you will just get a feel for how much to sow and water after a few tries.There is no establishment year; the first tray performs the same as any later tray. Expect to dial in seeding rate and watering over the first few cycles.
The arugula you will almost always grow as a microgreen is regular salad arugula (Eruca sativa). It is one of the fastest microgreens, ready in about 6 to 8 days, with a bold peppery flavor. Its seeds get sticky and gel-like when wet, so mist them instead of soaking, or they clump. There is also a wild or wasabi arugula (Diplotaxis) that grows more slowly and tastes even spicier. Whichever you pick, use seed sold for sprouting or microgreens, and cut while the little seed-leaves are open for the best flavor.Almost all arugula sold as a microgreen is standard salad arugula (Eruca sativa): a fast brassica, roughly 6 to 8 days to a peppery cut, sown at about 10 g per 1020 tray with no presoak. The seed is mucilaginous and forms a gel coat when wet, so mist it rather than soaking it, or it clumps and germinates unevenly. Wild or wasabi arugula (Diplotaxis tenuifolia) is a different genus that runs slower and tastes sharper; treat it the same way at sowing but expect a longer, spicier crop. Use untreated, microgreen-grade or food-safe seed, and cut at the cotyledon to first-true-leaf stage, before true leaves and fiber turn the flavor harsh.
The ladder troubleshoots from the gentlest solution to the strongest. Start with the gentlest option and only move on when and if it doesn't work.
Gnat larvae, the tiny worm-like young, live in mix that stays soaking wet, so let the top dry out a little between waterings. Once the leaves are up, water from the bottom (pour into the tray underneath) rather than misting the surface, and keep a little air moving over the tray. Arugula is cut so fast that gnats often do not get the chance to build up.The larvae develop in medium that stays wet, so allow the surface to dry between waterings as far as this crop permits and bottom-water once the tray has greened. Keep gentle air moving as well. Arugula's 6 to 8 day cycle works in your favor here, since most trays are harvested before numbers reach a level that matters.
Wash your trays and start each batch on fresh growing mix. That keeps gnats from one tray from carrying over into the next.Fresh medium and a sanitized tray at the start of each cycle take away the breeding sites, so a population does not carry from one batch into the next.
No spray for this one. Prevention is the control.
The ladder troubleshoots from the gentlest solution to the strongest. Start with the gentlest option and only move on when and if it doesn't work.
Do not sow too thickly. A crowded, stuffy stand is where this rot takes hold, and arugula's fine leaves already close in tightly on their own.Hold the seeding rate near the 10 g per 1020 tray this crop is sown at. The canopy is dense and fine to begin with, so overseeding compounds both the crowding and the trapped surface moisture that damping-off needs.
Aim for damp mix rather than wet mix. Once the leaves are up, water from the bottom (pour into the tray underneath) instead of wetting the leaves. Arugula seed turns sticky when wet and holds water right at the surface, so a soaked top is the main trigger.Aim for a wrung-sponge feel and nothing wetter, then switch to watering from below as soon as the tray greens, keeping the foliage dry. The mucilaginous seed coat keeps water sitting at the surface, which is the soil line where these fungi rot the seedlings.
Keep a small fan running so gentle air moves across the tray and the surface and stems do not sit damp. Still, stuffy air is half of what this problem needs to get going.Constant gentle airflow earns more here than on a looser crop: arugula's dense fine canopy closes over the surface early and holds humidity right at the soil line.
Microgreens are eaten raw and whole, so no spray is on the table here and prevention is the whole job. Wash and sanitize each tray before you sow in it. A heavily molded tray is not worth rescuing: get rid of it and start again on gear you have just cleaned.No rescue spray is available for a raw cut crop, so sanitizing trays between cycles is part of the control rather than housekeeping. Compost a tray that has molded badly and restart the cycle on clean equipment.
No spray for this one. Prevention is the control.
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