Why Is Your Kale Coming Up Prickly?

Kale continues riding a wave of popularity that started in the late twentieth century and has only grown since then. The vegetable is relatively easy to grow, and it’s packed with nutrients, causing many to label it as a superfood.

Your kale is coming up prickly due to genetics, and there’s little you can do about that until you plant again. Your kale may also be mislabelled and instead be a different plant— a closely related but still slightly different species.

Understanding the basics of genetic inheritance and how kale came to be what it is today can help you determine the likelihood that your kale will come up prickly. If it does, there are a few steps you can take to get around it.

Understanding Kale’s Growth as a Cruciferous Vegetable

Before you can fully understand why your kale is coming up prickly, it’s important to understand the growth cycle of the plant itself. This will help you to understand what phase of the cycle your kale plant is in, which will make it easier to diagnose the precise reason it is growing prickly.

Kale Is Cruciferous and Biennial

Cruciferous veggies include broccoli, cauliflower, Brussels sprouts, kale, and others. They are almost all members of the Brassica genus of plants. Their flowers usually have four petals, resembling a cross, which is where “cruciferous” comes from. 

Kale is a biennial plant, so it grows through two seasons before dying off. But its real benefit, agriculturally speaking, is that it grows late into the cooler months. 

Your lettuce, tomatoes, and cucumbers stop producing as the summer wanes, but kale continues growing in cooler temps, so you can still have harvestable crops long after your others have gone dormant for the season.

Kale Plants Become Inedible After Bolting

Incidentally, the second season of the kale plant’s life sees most of its energy going into bolting, which is what it’s called when plants begin flowering. Kale bolts to produce seeds, reproduce, and create the next generation.

Once kale begins to bolt, its status as an edible plant subsides. Since a bolting kale plant isn’t putting energy into growing leaves (the part we eat), the leaves it has and the few more it produces can be bitter, and other parts of the plant can become woody.

Certain Strains of Kale Grow Prickly

On the one hand, kale is kale. On the (technical) other hand, each kind of kale is either a different species in the same Brassica genus or is a variation of one species. There are seven main kinds of kale.

  • Chinese kale (Brassica oleracea, variation alboglabra) is also called Gai Lan or Chinese broccoli. Some chefs substitute it for common broccoli in their recipes. Its stalk is reminiscent of broccoli, but it has full, kale-like leaves. It is a good source of iron and vitamins A and C.
  • Common curly kale (Brassica oleracea, var. acephala) is the most widely used kale. It’s usually a dark green and has frilly leaves. 
  • Lacinato Kale (Brassica oleracea, var. palmifolia) is commonly known as dinosaur kale or Tuscan kale. This plant has bluish leaves that are entirely free of the lacy frills of common curly kale. It is high in vitamins B6 and K. The “dinosaur” moniker comes from the appearance of the leaves, which look a bit scaly, kind of like a dinosaur.
  • Ornamental kale (Brassica oleracea var. sabauda) sometimes goes by salad savoy. As its name states, this kale strain is a primarily decorative vegetable. It’s edible, but where it shines is in its color palettes. It can be white, yellow, pink, purple, and many shades in between. Its frilly leaves, like curly kale, can add a decorative flourish when used as a garnish.
  • Red Russian kale (Brassica napus, var. pabularia) also goes by Ragged Jack. The plant very often has thorny protrusions on it. Note that it is not part of the Brassica oleracea species. This fact will be important when we go back to the part about prickly kale. Red Russian kale is particularly cold-resistant.
  • Redbor kale (Brassica oleracea, var. acephala “Redbor”) is quite similar to common curly kale, though it is much redder. It is also more resistant to insects and diseases. It is usually prized more for its appearance in a meal presentation than its flavor, like ornamental kale, though it’s an edible plant.
  • Siberian Kale (Brassica napus), like Russian kale, is cold-resistant and not as closely related to most other kales. Also, like red Russian kale, this species can have thorns. It is not the best kale to eat raw, though doing so isn’t dangerous. This particular kale generally tastes better when cooked. 

Your kale may come up prickly because it is a Russian or Siberian strain of plant. It may also have genetic elements germane to the red Russian kale or the Siberian kale. Again, those are the two most distantly related to the other kinds. 

Even if you don’t have Siberian kale, though, you may have spines or thorns on your kale because genetic markers from that strain appear in the strain of kale you have. Remember that since all these varieties are from the Brassica genus, they can cross-pollinate. 

When we cross-pollinate plants on purpose, we make hybrid plants and vegetables. When nature does it on its own, we sometimes get DNA from one plant expressed in another. 

Mendelian Genetics Can Explain Prickly Kale

Gregor Mendel was an Austrian monk who, in the 19th century, was not satisfied with the accepted idea that offspring were a blend of the essences of their parents. He set out to prove this and, in doing so, became the father of modern genetics.

Mendel used pea plants and tracked the traits that successive generations displayed. He kept copious records of the characteristics of his plants, then looked at their offspring to see what features got passed on to them.

From his work, we get the concept of dominant and recessive genes (Mendel did not use the term “gene,” but his work essentially showed what they were and how they worked). 

A few decades after Mendel, a British geneticist named Reginald Punnett developed the Punnett square as a visual representation of how Mendelian genetics worked. Here is an example:

If a kale plant we call Parent 1 (top row, horizontal) has the dominant gene (T) for no thorns and the recessive gene (t) for thorns, Parent 1 will be a thorn-free kale plant. Parent 2 has the same genetic makeup, Tt, and has no thorns.

The Punnett square shows us that their offspring might get a double-dose of the T gene, might get one T and one t, or might get two t’s. If there is no dominant gene (T) present, the recessive one (t) will express, and that offspring will have thorns. 

Parent 1 Parent 2Tt

We conclude from this genetic makeup that any offspring of these two parents has a 25% chance of expressing the recessive gene. 

As we crossbreed different plants, we make it possible for a recessive gene from, say, a Siberian kale plant to find its way into our Chinese kale. Given the right circumstances, the gene can express, giving us thorny kale. 

Misidentification Often Explains Thorny Kale

A much less scientific or glamorous reason your kale may have thorns is that it isn’t kale at all. Turnip leaves look like kale, but they have thorns. The scientific name for the turnip is Brassica rapa, so the two plants are closely related. 

It wouldn’t be an outrageous turn of events for seeds to have been misidentified before you obtained them and planted them in your garden.

Prickly Kale Is Still Edible

Regardless of why your kale is coming up prickly, it’s still edible. If it’s turnip greens and not kale, that’s still an edible plant. If your kale is prickly and actually kale, rest assured that the thorns will soften in the cooking process.

Prickly kale isn’t ruined, and it’s not inedible or poisonous. It’s not something you want to eat raw simply because getting poked in the mouth by your food isn’t fun.


The two main reasons your kale may come up prickly are that it isn’t kale at all, or it has some genetic material from thorny kale varieties like red Russian or Siberian kale.

There’s no way to get your kale to stop growing the little thorns, but you can easily cook them into a tender state that won’t interfere with the flavor or consistency of the kale you love to eat.

Alexander Picot

Alexander Picot is the principal creator of TheGrowingLeaf.com, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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