Short answer: fill a tray with 1 inch of moist potting mix. Sprinkle about 20 g of broccoli seed evenly over a 10 × 20 inch tray (half that for 10 × 10). Mist it, cover it and keep it dark for 2 to 3 days. Then uncover it, give it bright light and water from below daily. Cut above the soil at 7 to 12 days, once the seed leaves are open.
Why grow broccoli microgreens?
- Easy. The seed sprouts fast and evenly, so it's a great first microgreen.
- Mild taste. Fresh and slightly peppery, like a gentle broccoli.
- Glucoraphanin. Broccoli microgreens are a good source of the compound your body turns into sulforaphane.1
- Fast. Ready in about 7 to 12 days.
If you'd rather grow them in a jar, see broccoli sprouts. For a side-by-side comparison, read broccoli sprouts vs broccoli microgreens.
What you need
- Broccoli seed sold for sprouting or microgreens
- A 10 × 20 inch tray set (one tray with holes, one without), or a 10 × 10 set
- About 1 inch (2.5 cm) of fine potting mix, coco coir or a grow mat
- A cover: a spare tray or a flat board
- A spray bottle, scissors, and a bright window or an LED light
How much seed to use
Published seeding rates for a 10 × 20 inch tray range from about 13 g (Johnny's trial average) to 28 g (Utah State Extension).2 About 20 g is a good starting point. Use roughly half for a 10 × 10 tray.
- Too thin: sparse, leggy greens.
- Too thick: mold at the base and seed hulls stuck on leaves.
How to grow broccoli microgreens, day by day
- Day0
Prepare the tray
Fill the holed tray with about 1 inch of potting mix, press it flat and water it until evenly damp. Set it inside the solid tray.
- Day0
Sow dry
Sprinkle the seed evenly over the surface. Press it lightly onto the soil and mist well. No soaking is needed.
- Day0–3
Blackout
Cover with a second tray. Mist once or twice a day. Fine white root hairs appear around day 2; they're normal.
- Day3
Uncover and give light
When the seedlings lift the cover, take it off. Move the tray to a bright window or under an LED light for 12 to 16 hours a day.
- Day3–10
Water from below
Pour about a cup of water into the solid tray once a day. Let the roots drink for 10 to 15 minutes, then tip out the rest.
- Day7–12
Harvest
Cut just above the soil when the seed leaves are fully open. Harvest before the first true leaves get large.
Sprouting.com gives broccoli 7 to 10 days as a microgreen.3
Root hairs aren't mold. Broccoli grows fuzzy white root hairs on day 2 or 3. Mist them: if the fuzz collapses, it's root hairs. Mold is gray or colored, patchy and smells musty.
Light and temperature
Broccoli microgreens grow best at 65 to 75°F (18 to 24°C). Give them bright light once they're uncovered. With too little light, they stretch tall and pale. In winter, an LED shop light 2 to 4 inches above the tray makes a big difference. See do microgreens need grow lights?
Problems and fixes
| Problem | Likely cause | Fix |
|---|---|---|
| Patchy germination | Uneven sowing or dry seed during blackout | Sow evenly and keep misting under the cover |
| Mold at the base | Too thick, too wet, still air | Sow a little thinner, water from below, add a fan |
| Tall, pale, floppy | Too little light | Brighter window or a closer light |
| Hulls stuck on leaves | No weight, dry tops | Mist before uncovering. Brush off hulls at harvest |
| Yellow leaves | Harvested late or low light | Cut earlier and give more light |
Broccoli microgreens and sulforaphane
Broccoli is famous for glucoraphanin, which becomes sulforaphane when you chew the plant. In a 2023 study, broccoli microgreens had glucoraphanin levels similar to those reported for broccoli sprouts. People who ate them made sulforaphane in amounts comparable to sprout studies.1 Chew them well, or blend them into pesto and smoothies, to help sulforaphane form. Read more in broccoli sprouts benefits.
How to store broccoli microgreens
Cut only what you'll use. Store them dry in a container lined with a paper towel in the fridge. They keep about 5 to 7 days. Rinse them just before eating.
How to eat broccoli microgreens
- Salads and grain bowls: a mild, fresh topping.
- Sandwiches and wraps: in place of lettuce.
- Smoothies: a handful blends in easily.
- Pesto: see microgreen pesto three ways.
- Eggs and soups: scatter them on top just before serving.
Where to buy broccoli seed
We link to broccoli seed from Sprouting.com, sold for sprouts and microgreens. For jar sprouts with more variety, their Broccoli Brassica Blend mixes broccoli with clover, radish, mustard and arugula.
Seeds in this article
Frequently asked questions
How long do broccoli microgreens take to grow?
About 7 to 12 days from sowing. Sprouting.com gives 7 to 10 days. Harvest when the two seed leaves are fully open, before the first true leaf grows large.
How much broccoli seed do I need per tray?
About 13 to 28 g for a 10 × 20 inch tray. Published charts range from Johnny's trial average of about 13 g to Utah State's 28 g. Start at about 20 g and adjust.
Should I soak broccoli seeds for microgreens?
No. Broccoli seed is small and sprouts well when sown dry on moist soil. Mist it well after sowing and keep it covered for the first few days.
Do broccoli microgreens have sulforaphane?
Yes. A 2023 study found broccoli microgreens had similar glucoraphanin levels to those reported for broccoli sprouts, and people who ate them produced sulforaphane. Chew them well or blend them to help it form.
Do broccoli microgreens regrow?
No. Once cut, broccoli microgreens don't grow back. Compost the roots and start a new tray. For a steady supply, sow a small tray every 4 or 5 days.
Written by Michael
A passionate sprouting professional sharing practical tips for growing sprouts and microgreens at home. More about Michael
Sources
- Sulforaphane bioavailability in healthy subjects fed a single serving of fresh broccoli microgreens. Foods, 2023 (PubMed 37893677). Link
- CropKing. Microgreen Seed Density Charts (seeding rates per 10 × 20 inch tray). Link
- Sprouting.com (Mumm's Sprouting Seeds). Product pages: days to sprout, soak time and yield for each seed. Link
