Salad Gardening
Published October 26, 2022 by Nicole Burke

Why Aren't My Cabbages Forming a Head?

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cabbages
cabbage growing
Why Aren't My Cabbages Forming a Head?

Grow Your Own Cabbage

I've been growing cabbages for years, and there have been so many times when they never quite turn out the way I was hoping. I'll end up with a lot of leaves but not necessarily that nice, tight head of great leaves that you'd expect from a heading lettuce like cabbage.

So this year, I've planted about 20 Napa cabbages, which seems like a lot, I know. But I love Asian food. I lived in China for two years out of college, and if I could have stir-fried Napa cabbage everyday, I think I'd be a happy person. I'm already happy, but I'd be even happier.

This year, I'm doing a few things to make sure that I get heads formed on my Napa cabbages. I want tons of nice, leafy greens on the inside of these plants. And there are steps we can take to try to speed up the formation of the cabbage head—mainly, know your temperatures, water enough, and cut back on the nitrogen.

how cabbage grows

Reason #1 Cabbages Won't Form a Head

Cabbage Won't Form a Head If the Temperature Isn't Right

Cabbages are in the brassica family, and this is a cool-season bunch. Very few of them thrive when it's hot outside. If temperatures rise over 80 degrees F consistently, cabbage plants will either stop growing or they'll bolt (produce flowers and then go to seed).

The difficult thing about cabbage is that it also doesn't like to grow when it's too cold (below 45 degrees regularly). So, you're looking for the ideal temperature range between 45 and 80 degrees to grow cabbage under its preferred conditions. The problem is you need about 60 days in this ideal temperature range for your cabbages to grow in the garden.

For many of us, that means there's a short window of time during which cabbage plants love the weather, and outside of that window, they often just won't form a head.

Temperature Solution

You can trick cabbage into thinking it's growing under its ideal conditions a bit longer by using frost cloth on cold days and shade cloth on warmer days. Beyond that, you've got to work with the weather you've got.

Why Aren't My Cabbages Forming a Head?

Reason #2 Cabbages Won't Form a Head

Cabbage Won't Form a Head If It's Not Getting Enough Water

The next thing to keep in mind to get cabbage plants to form a head is water. A common reason why cabbage isn't forming a head is that it's not being properly watered. Water is so important for all lettuces really, but especially for cabbage, which is 92 percent water in its makeup. As you can imagine, any cellular growth for a plant that's mostly water will require... a lot of water.

So you really want to make sure that you're watering on the regular. Avoid over-watering, but you do want the ground to stay moist underneath these plants.

Water Solution

Use drip line irrigation on a timer to deliver consistent water to these salad greens just where they like it, on the soil, not the leaves.

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Reason #3 Cabbages Won't Form a Head

Cabbage Won't Form a Head If It's Getting Too Much Nitrogen

Generally, if you have a nitrogen-rich soil, then you're going to get lots of leaves but not necessarily the formation of a head when growing a heading lettuce like cabbage.

Now, don't get me wrong. All those greens formed thanks to nitrogen are edible, delicious, and nutritious. But if you're goal is a compact head, then you'll have to switch up your fertilizing.

Nitrogen Solution

Add a little phosphorus-rich fertilizer. The idea here is to push more phosphorus instead of nitrogen into the roots of these cabbage plants so that the focus is more on forming that nice head rather than just giving you all these greens.

cabbage heads

The Next Steps to Encourage Cabbage to Form a Head

Prune Your Cabbage

Once you've taken the above three steps to ensure your cabbages form a head, you get to come in and be the director. You get to tell the plants where to focus its efforts. To do that, we're going to prune our cabbage plants.

Start by pruning those older, larger leaves on the outside of the cabbage plant. You'll be able to tell that these leaves are not really going to be part of the cabbage head because they've already opened and pushed outward. If you plant intensively like I do, pruning these older leaves back will mean that there's more room in the garden for other things.

All brassica plants push their newest growth from the heart and center of the plant. We want hundreds of little leaves forming in the centers of these cabbage plants to get a nice, tight head. When we cut back the exterior leaves, we're telling the plant to put all its energy into forming new leaves instead of making the edge leaves larger.

By the way, keep all the leaves you're pruning because they're all edible. Bring them inside to enjoy!

cabbage heads

Fertilize Your Cabbage Plants

I recommend using an organic ocean-based product like Neptune's Harvest Fish and Seaweed Fertilizer. If you're shopping around for a fertilizer, just be sure to look at the three numbers (N-P-K). Remember, we don't want a lot of nitrogen (the first number). And be sure to read the directions to get the right dosage. Just mix up your fertilizer and pour it around the base of the plants. Do this about once a week.

And that's it! Now you're on your way to ensuring your cabbages form a head!

Thanks for helping me bring back the kitchen garden, one cabbage plant at a time.

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Why Aren't My Cabbages Forming a Head?