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Fermented Vegetables & Fruit

How to Ferment Collard Greens: A Simple 2% Salt Method

By Updated 2 min read

At a glance

To ferment collard greens, remove the ribs, shred the leaves into 5 mm ribbons, weigh them and massage in 2% of their weight in salt (20 g per kg). Pack tightly into a jar, topping up with 2% brine if the greens don't make enough juice, add a weight, and ferment at 18–22°C for 5–10 days until tangy. Then refrigerate.

  • Use 2% salt by weight of the trimmed greens (20 g per kg).
  • A teaspoon of fine salt weighs about 6 g – spoon measures easily over-salt.
  • Shred thin and top up with 2% brine if the greens don't cover themselves.
  • Ferment 5–10 days at 18–22°C, then refrigerate.
  • Leafy greens contain nitrate; we don't suggest fermented greens for babies.

Ferment profile

Fermentation
Lactic acid
Main microbes
Lactic acid bacteria from the leaves (Leuconostoc, Lactiplantibacillus and others)
Live cultures
Depends on preparation
Alcohol
None / trace

Collard greens ferment much like cabbage – they’re the same species, Brassica oleracea. Shredded into thin ribbons, massaged with salt and packed under their own juice, they turn tangy, tender and savory in about a week, a little like a leafy sauerkraut. The recipe card below uses 2% salt by weight: 20 g per kg of trimmed greens, about 10 g for a 500 g batch.

Weigh the Salt

Salt is what lets the lactic acid bacteria on the leaves outcompete spoilage microbes (NCHFP), so it’s worth getting right. Spoon measures are risky: a teaspoon of fine salt weighs roughly 6 g, so “a teaspoon per 100 g of greens” would be about 6% – three times too salty. Weigh the trimmed greens and take 2% of that.

Collards Need a Little Help

  • Shred thin: remove the tough center ribs and cut leaves into ribbons about 5 mm wide. Thin ribbons release juice and pack down better.
  • Massage, then wait: work the salt in for a few minutes and let the greens sit 20–30 minutes before massaging again.
  • Top up if needed: collards are tougher and drier than cabbage, so they often don’t make enough liquid. Add a 2% brine (10 g salt in 500 ml water) to cover by about 2 cm.
  • Keep everything under: use a weight; exposed leaves are where mold starts.

Garlic, chili flakes, mustard seeds or a few shreds of onion or carrot are good additions. A flat white film is usually kahm yeast and can be skimmed; fuzzy colored mold, slime or a rotten smell means discard the batch. Our troubleshooting guide covers the rest.

Leafy Greens and Babies

Leafy greens contain nitrate, which bacteria can convert to nitrite during storage and fermentation; nitrite can cause methemoglobinemia, and young infants are most at risk (Chan, 2011). Nitrite falls again as a ferment becomes sour, but as with our fermented spinach, we suggest not giving fermented greens to babies, and eating them once they’re properly sour.

Serving

Eat fermented collards as a tangy side with beans, cornbread, rice or grilled meats, chop them into grain bowls, or warm them through at the end of cooking a pot of greens. Uncooked, they contain live lactic acid bacteria; cooked, they keep the flavor but not the live cultures (Marco et al., 2021). Nepal’s gundruk is a very different way to ferment leafy greens, and sauerkraut uses exactly the same method with cabbage.

Recipe: Fermented Collard Greens (2% Salt)

Makes
One 1-litre jar
Hands-on
30 min
Fermentation
5–10 days at 18–22°C
Salt
2% of the greens' weight; 2% brine to top up
Temperature
18–22°C (64–72°F)
Difficulty
Easy

Equipment

  • Scale
  • Large bowl
  • 1-litre jar
  • Fermentation weight
  • Lid or airlock

Ingredients

  • About 500 g collard greens (trimmed weight, ribs removed, shredded 5 mm)
  • 10 g non-iodized salt (2% of the greens)
  • 2–3 garlic cloves (sliced, optional)
  • ½ tsp each chili flakes and mustard seeds (optional)
  • As needed 2% brine (10 g salt in 500 ml water)

Method

  1. Weigh the shredded greens and measure 2% of their weight in salt.
  2. Massage the salt into the greens for 3–5 minutes, rest 20–30 minutes, then massage again until juicy.
  3. Pack into the jar a handful at a time with the garlic and spices, pressing down hard after each layer.
  4. If the juice doesn't cover the greens, top up with 2% brine. Add a weight.
  5. Close loosely or fit an airlock and keep at 18–22°C. Press down daily if leaves rise.
  6. Taste from day 5. When pleasantly sour (usually 5–10 days), close and refrigerate; eat within a few months.
  7. Skim a flat white film if it forms; discard the batch if fuzzy colored mold grows, or it turns slimy or smells rotten.

Frequently asked questions

How much salt do I need to ferment collard greens?

2% of the trimmed greens' weight – 20 g per kg, about 10 g for 500 g. Weigh it; spoon measures easily make it several times too salty.

How long do collard greens take to ferment?

Usually 5–10 days at 18–22°C. Taste from day 5 and refrigerate when they're as sour as you like.

My collards didn't make enough brine. What do I do?

That's common with tough greens. Top up with a 2% brine (10 g salt in 500 ml water) so everything is covered.

Can I cook fermented collard greens?

Yes – they're good warmed into a pot of greens or beans. Cooking keeps the tangy flavor but kills the live bacteria.

Can I ferment kale or mustard greens the same way?

Yes. Kale, mustard greens and turnip greens all ferment well with the same 2% salt method.

How long do fermented collards keep?

Several months in the fridge, kept under their liquid. They slowly soften and get more sour.

Sources

  1. National Center for Home Food Preservation. General information on fermenting. Link
  2. Chan TY (2011). Vegetable-borne nitrate and nitrite and the risk of methaemoglobinaemia. Toxicol Lett 200(1–2):107–108. Link
  3. Marco ML et al. (2021). The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on fermented foods. Nat Rev Gastroenterol Hepatol 18(3):196–208. Link
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