About Microgreens

The real name to learn first is Brassica rapa, the turnip family line most mixes use. Microgreens are seedlings cut at the first true leaf, about 2 inches tall, 7 to 14 days after sowing. A 10 by 20 inch tray holds 1 to 2 ounces of dry seed and yields 8 to 12 ounces of greens. They need no mature root system, so a 1 inch depth of medium is enough. Expect a 30 to 40 percent weight gain in water at soak, and sow dense because nearly every seed is meant to grow. Pea, sunflower, and radish lead the beginner trays because they germinate above 90 percent. Fill the tray to the rim and press the seed into contact, since a gap of 1/8 inch drops emergence by half. Two trays on a shelf give a fresh cut every 3 to 4 days once the sow dates stagger by a week.

What EC and pH Work for Microgreens?

Run 1.0 to 1.5 EC, lower than full lettuce, because seedlings are sensitive to salt. pH 5.8 to 6.2 matches the rest of the category. Mix 1 teaspoon of two part nutrient per 2 gallons of water for the soak and the early misting. After day 3 the cotyledons feed on light more than solution, so you can drop feeding to a light mist once daily. Refresh the reservoir every 7 to 14 days if you use a passive wick, and keep the medium damp but never flooded or the stems rot at the base. Test the soak water before you sow, because a pH of 6.8 at mix time shows up as purple stems by day 6. A cheap drop test kit reads within 0.2 and costs less than one tray of lost seed.

How Many Days to Harvest?

Most mixes cut at 7 to 14 days. Pea shoots take 10 to 14 days and reach 3 to 4 inches. Sunflower takes 8 to 12 days under 14 to 16 hours of light. Radish is fastest at 6 to 9 days. Mark the sow date on the tray and check height daily after day 5. Cut with clean scissors just above the medium, and a second tiny flush is possible only on pea and sunflower if you leave the crown intact. Stagger three trays 4 days apart and you harvest twice a week with no gap. A single 10 by 20 inch tray of sunflower returns 10 to 14 ounces, enough for 4 sandwiches, at a seed cost near 0.50 dollars.

Light and Temperature

Give 14 to 16 hours of bright light, with 4 to 6 hours direct if you can. A 20 watt LED over a shelf grows solid color without stretching. Hold the air at 65 to 72 F (18 to 22 C) and the medium near 68 F (20 C). Below 60 F (15 C) germination stalls, and above 80 F (27 C) damping off spreads fast. Blackout the tray for the first 3 to 4 days with a lid so stems reach for dark and grow tall and straight before light exposure. After the lid comes off, raise the LED to 4 to 8 inches above the tray so the stems do not lean. A small circulating fan on low for 10 minutes each hour hardens the crop and blocks the fungal wilt that kills trays at day 5.

Why Do Microgreens Fall Over?

Collapse comes from three causes, and all are fixable. Too little light makes stems weak and they bend by day 4. Poor air flow lets fungal wilt take the crown overnight. Overwatering at the base rots the stem where it meets the medium. Fix each by raising light to 16 hours, running a small fan for 10 minutes hourly, and misting instead of pouring. Once a tray collapses, compost it and start a fresh 10 by 20 inch tray rather than rescue the lost seedlings, because the spores linger in the medium. Watch the base of each stem at day 4, since a thin brown ring there means the tray is already lost and should be pulled before it spores the shelf.

Which Medium Should You Use?

Pick coco coir or a hemp mat for a clean first run. Coco holds 8 to 10 times its weight in water and wicks evenly across a 10 by 20 inch tray. Hemp mats sit flat and trim clean, which speeds harvest and compost. Soil works but carries more damping off risk, so skip it until your numbers are steady. Layer the medium 1/2 to 1 inch deep, pre wet it to field capacity, and drain the excess so the tray bottom stays dry for 2 to 3 days after sowing. A dry bottom is the single biggest factor in avoiding the stem rot that ends most first trays.

Frequently Asked Questions

Q: Do microgreens need a pump?

A: No. A passive wick or bottom tray supplies all the water a 14 day crop needs. Pumps add heat and complexity with no yield gain for such a short cycle.

Q: Why are my leaves pale?

A: pH above 6.5 blocks nutrient uptake, the same fault seen in lettuce. Correct to 6.0 and the next tray greens properly from the start.

Q: Can I reuse the medium?

A: No. Spent coco or soil carries damping off spores, so use a fresh 1 inch layer for every tray to protect the next sowing from collapse.

Microgreens teach the numbers faster than any other crop. Hold pH near 6.0, light at 16 hours, and the medium under 72 F, and a 10 by 20 inch tray pays back in two weeks. Start with our hydroponics guide and the care schedule tool, then scale to five trays once your first cut proves the timing fits your shelf.