Sarson Ki Khali (Mustard Cake) for Plants: How to Use It Properly

If your grandmother grew roses, she used sarson ki khali. Mustard cake has been the standard fertilizer in Punjabi gardens for longer than anyone has been selling bottled plant food, and it still does the job. The problem is that most of the advice about how to use it has been passed on by word of mouth, and half of it is wrong.

This is how it actually works, how much to use, and the two mistakes that make people give up on it.

What sarson ki khali is

When mustard seed is pressed for oil, what's left is a dry, hard cake. Ground up, that cake is around 5 percent nitrogen by weight, with a bit of phosphorus and potassium and a fair amount of protein that soil microbes break down over a few weeks. It's a slow-release nitrogen feed, which is exactly what a plant wants for leaf and stem growth.

Nitrogen is the nutrient that makes things green and makes them grow. If your plant is putting out small, pale leaves and hasn't been fed in months, nitrogen is usually what's missing, and mustard cake is one of the cheapest ways to supply it.

Two ways to use it

Dry, mixed into the soil

This is the simpler method and the one we'd start with. Take one or two tablespoons of mustard cake powder for an 8 to 10 inch pot, scratch it into the top inch of soil around the plant (not touching the stem), and water it in well. Repeat every three to four weeks during the growing season.

For garden beds and roses in the ground, use about 100 grams per square metre worked into the soil surface. For a lawn, 50 grams per square metre broadcast before watering.

It takes a week or two before you see anything, because microbes have to break it down first. That's normal.

As a liquid tea

This is the method your grandmother used, and it works faster because the nutrients are already dissolved when they reach the roots. It also smells, which is why some people stop doing it.

Put 50 grams of mustard cake in a litre of water in a bucket with a lid. Leave it three or four days somewhere outside. It will ferment and it will stink. That's the point. After three days, strain it and dilute the liquid with about five litres of clean water. Pour that around the base of your plants. One batch does a dozen medium pots.

Don't use it undiluted. Strong mustard tea straight from the bucket will burn roots the same way a chemical fertilizer would. And don't leave it fermenting for more than five or six days. Past that it goes from useful to foul and starts breeding flies.

The two mistakes

The first mistake is using too much. Mustard cake is cheap, so people pile it on. Too much nitrogen gives you a plant that's all soft leaf and no flower, and in a pot it can heat the soil as it breaks down and damage roots. One or two tablespoons per pot. If you think you need more, you need to feed more often, not more at once.

The second mistake is using it on the wrong plants at the wrong time. Mustard cake is a nitrogen feed. It's for leaf growth. Give it to a rose in October when you want flowers and you'll get a big leafy bush with no blooms. For flowering and fruiting you want phosphorus, which is bone meal, not mustard cake. Use mustard cake through spring and summer when the plant is building itself, then switch to bone meal as it moves toward flowering.

Which plants like it

Roses through the growing season, before you switch to bone meal for flowering. Hibiscus, which is a hungry plant and takes a lot of nitrogen. Money plants, monsteras, and other foliage houseplants. Chilli and tomato seedlings up to the point where they start setting fruit. Leafy vegetables like palak and methi, where the leaf is the whole point.

Go easy on it with cacti and succulents, which don't want much nitrogen at all, and with anything that's about to flower.

Mustard cake or Master Blend?

People ask us this a lot. The Master Blend is a balanced all-in-one with neem cake for soil pests and humic acid to unlock what's already in the soil. It's what you use when you want one product for everything and don't want to think about it.

Mustard cake is a single-ingredient nitrogen feed. It's cheaper per kilo and it does one thing well. If you already have a plant that needs a specific nitrogen push, or you're feeding a whole bed of leafy greens, it's the better tool. Plenty of people use both: Master Blend as the monthly routine, mustard cake tea as the extra boost when something's slow.

Storing it

Keep the powder dry and sealed. Damp mustard cake goes mouldy quickly and attracts ants. Use a dry spoon every time, and don't leave the pouch open in a humid kitchen.

If you're unsure whether your plant needs nitrogen or something else, send a photo on WhatsApp at 0370-9145600 and we'll tell you which one.