Kohlrabi microgreens are one of the prettiest crops you can grow on a tray: thin stems in shades of lilac or pale green, topped with smooth, heart-shaped leaves. If you want to know how to grow kohlrabi microgreens, the good news is that they behave a lot like broccoli. The seeds are small, need no soaking, sprout in a day or two and are ready to cut in about 8–12 days. The flavor is mild, sweet and slightly cabbage-like, so they suit almost any dish.
This guide gives you exact numbers for a standard 10×20 tray, a day-by-day timeline, the variety choice that decides stem color, and a troubleshooting table for the problems kohlrabi growers run into most often.
Key takeaways
- Sow about 20–28 g of kohlrabi seed per 10×20 tray (roughly 10–14 g for a 10×10). No soaking needed.
- Keep trays at 65–75°F (18–24°C); seeds germinate in 1–3 days.
- Use a 3–4 day blackout, then give 12–16 hours of light a day.
- Harvest at 8–12 days, when the first two leaves are fully open and stems are 2–3 inches tall.
- Choose a purple variety (such as Purple Vienna) if you want purple stems; white/green types give pale stems.
Kohlrabi microgreens at a glance
| Seed per 10×20 tray | 20–28 g (about ¾–1 oz) |
| Seed per 10×10 tray | 10–14 g |
| Soak | Not needed |
| Germination | 1–3 days |
| Blackout | 3–4 days |
| Light after blackout | 12–16 hours per day |
| Ideal temperature | 65–75°F (18–24°C) |
| Harvest | Day 8–12, at 2–3 inches tall |
| Regrows after cutting? | No |
| Flavor | Mild, sweet, like a gentle cabbage or broccoli |
Not sure how much seed your tray needs? Plug its size into the TrayGrown microgreens seed calculator and it will scale the amount for you.
Choosing kohlrabi seed: purple vs white varieties
Kohlrabi is a brassica, a close cousin of cabbage, kale and broccoli. For microgreens you are not growing the swollen bulb-like stem the vegetable is known for; you harvest the seedling long before that forms. What the variety does change is stem color:
- Purple types (for example Purple Vienna) usually give lilac to violet stems. The color is strongest under good light.
- White or green types (for example White Vienna) give pale green to white stems with the same green leaves.
Both taste very similar. Buy seed that is sold for sprouting or microgreens, or at least untreated seed. Garden packets are often small and sometimes coated with fungicide, which is not meant for crops you eat as seedlings. Seed bought in bulk for microgreens is also far cheaper per tray.
What you need
- One 10×20 tray with drainage holes and one without holes (for bottom watering), plus a spare tray or lid to use as a blackout cover.
- Growing medium: about 1–1.5 inches of a fine potting mix or coco coir, or a hemp grow mat. See our comparison of growing media if you are undecided.
- A spray bottle for misting seeds.
- A light source: a bright window can work, but an LED shop light or grow light gives straighter, more even greens.
- About 20–28 g of kohlrabi seed and a kitchen scale.
How to grow kohlrabi microgreens, step by step
Step 1: Prepare the tray (day 0)
Fill the holed tray with 1–1.5 inches of moist growing medium. Level it gently with your hand or a piece of cardboard, but do not pack it hard; a flat, slightly firm surface helps the seed make even contact. The mix should feel like a wrung-out sponge, not dripping. If you use a hemp mat, soak it until it is fully saturated and let the excess drain away.
Step 2: Sow the seed (day 0)
Weigh out 20–28 g of seed for a 10×20 tray. Use the lower end if you are new to kohlrabi or your room is humid, because dense trays of small brassica seed are more prone to mold. Sprinkle the seed evenly across the surface, working in a grid so no area is bare or piled up. You want seeds close together, touching in places, but not stacked in layers. Our guide on how much seed to use per tray explains how density affects yield and airflow.
Mist the seeds well so they settle into the surface. There is no need to cover them with soil, and kohlrabi seed does not need soaking; soaking small brassica seed mainly makes it sticky and harder to spread. (For which crops do benefit, see our guide to soaking microgreen seeds.)
Step 3: Blackout and weight (days 1–4)
Cover the tray with a second tray or lid to block light. Many growers set a light weight on top (a few pounds is plenty for a 10×20 tray) so the seedlings push against it. This encourages strong roots and stems that stand up evenly when the cover comes off. Mist once or twice a day if the surface looks dry.
Keep the tray at 65–75°F (18–24°C). Germination usually starts within 24–48 hours, and by day 3 or 4 you should see a mat of pale yellow seedlings about an inch tall. That pale color is normal during blackout and turns green within a day of light. Read more about timing in our microgreens blackout period guide.
Step 4: Uncover and give light (days 4–8)
Remove the cover once most seedlings are 1–1.5 inches tall and pushing up. Place the tray under a light for 12–16 hours a day. With an LED fixture, a distance of roughly 6–12 inches above the canopy works for most setups. If you rely on a window, turn the tray every day so the stems do not lean.
From now on, water from the bottom: pour about 1–2 cups of water into the solid tray and set the holed tray inside it for 10–15 minutes, then lift it out and drain. Bottom watering keeps leaves dry, which matters with dense brassicas. Check the weight of the tray each day; when it feels noticeably lighter, it is time to water. Our microgreens watering guide covers this in more detail.
Step 5: Harvest (days 8–12)
Kohlrabi microgreens are ready when the two seed leaves (cotyledons) are fully open and the stems are about 2–3 inches tall. For the mildest, most tender texture, cut before the first true leaf grows large. The first true leaf has a different, jagged shape and a slightly stronger cabbage taste; a few on the tray are fine.
Stop watering 12–24 hours before harvest so the leaves are dry. Cut with sharp scissors or a knife about half an inch above the medium, gathering a handful at a time. Kohlrabi will not regrow from the cut stems, so compost the roots and medium and start a new tray. See how to harvest microgreens for clean cutting and storage tips, and do microgreens regrow? for why most crops are single-cut.
Kohlrabi microgreens timeline
| Day | What you should see | What to do |
|---|---|---|
| 0 | Seed sown on moist medium | Mist, cover, add light weight |
| 1–2 | Seeds swell, tiny white roots appear | Mist if dry; keep 65–75°F (18–24°C) |
| 3–4 | Pale yellow seedlings about 1 inch tall | Remove cover, start 12–16 h of light |
| 5–7 | Leaves turn green, stems color up | Bottom water when tray feels light |
| 8–12 | Leaves fully open, 2–3 inches tall | Stop watering the day before, then harvest |
Troubleshooting kohlrabi microgreens
Kohlrabi is forgiving, but it shares the usual brassica problems. Use this table to match what you see to the likely cause.
| Problem | Likely cause | Fix |
|---|---|---|
| White fuzz at the base of stems | Usually root hairs, which are normal; real mold looks wet or slimy and spreads | Mist the area: root hairs collapse, mold stays. See mold vs root hairs |
| Gray, wet patches that spread | Mold from too much seed, standing water or poor airflow | Sow less seed, bottom water only, run a small fan |
| Long, pale, floppy stems | Too little light or blackout left on too long | Move light closer or add hours; see microgreens falling over |
| Stems stay green, not purple | White/green variety, or weak light | Buy a purple variety; give stronger light |
| Patchy germination | Old seed, uneven sowing or a dry surface | Test seed first; mist more; see microgreens not germinating |
| Yellow leaves after uncovering | Normal for 12–24 h; longer means low light | Give it a day; if still yellow, see yellow microgreens |
Storing and using kohlrabi microgreens
Store dry, unwashed greens in a sealed container lined with a paper towel in the fridge, ideally around 34–40°F (1–4°C). They usually keep well for about 5–7 days. Rinse just before eating.
Because the flavor is mild, kohlrabi microgreens work almost anywhere: on sandwiches, in salads, on top of soups and tacos, folded into omelets, or as a garnish where you want color. Purple stems look especially good against white plates and pale foods like rice or eggs.
Kohlrabi vs other brassica microgreens
| Crop | Seed per 10×20 | Harvest | Flavor |
|---|---|---|---|
| Kohlrabi | 20–28 g | 8–12 days | Mild, sweet cabbage |
| Broccoli | 18–25 g | 8–12 days | Mild, slightly earthy |
| Radish | 30–40 g | 6–10 days | Spicy, peppery |
| Red cabbage | 20–28 g | 9–14 days | Mild, cabbage |
If you like kohlrabi, broccoli microgreens grow on almost the same schedule, and radish microgreens are a faster, spicier option. New to growing? Start with our complete beginner guide to growing microgreens.
Frequently asked questions
Do kohlrabi microgreens need to be soaked?
No. Kohlrabi seed is small and germinates quickly on a moist surface. Soaking makes the seed clump together and harder to spread evenly.
How long do kohlrabi microgreens take to grow?
Most trays are ready in 8–12 days from sowing, depending on temperature and light. Cooler rooms can push harvest toward 14 days.
Why are my kohlrabi microgreens not purple?
Stem color depends mostly on the variety. White or green kohlrabi gives pale stems. Purple types color best under bright light, so weak light can also make them look washed out.
Can I grow kohlrabi microgreens without soil?
Yes. They grow well on hemp mats or other grow pads because they are harvested young. Keep the mat evenly moist and bottom water. See growing microgreens without soil.
Will kohlrabi microgreens grow back after cutting?
No. Like other brassicas, they are a single harvest. Compost the roots and sow a fresh tray.
