Kale is an easy vegetable to grow and ideal for cooler climates because exposure to frost makes the leaves sweeter. Most common varieties of kale are biennial, which means that these plants complete their life cycle over two years.
Kale seeds will germinate in around 5 to 8 days. In around 2 weeks, you’ll see the first true leaves grow. It will take around 2 months from the planting of the seeds before you can start to harvest the first leaves. You can also grow baby kale for leaves that are ready to harvest in around 30 days.
Kale Growing Stages
Here’s a rundown of the different growth stages that kale goes through.
Seed Germination Or Sprouting Stage
Whether you plant the seeds in a seedling tray or straight into the ground, it should take around 5 to 8 days for them to germinate. You can help speed up this process by soaking the seeds in tepid water for around 24 hours before you sow them.
Additionally, if you have a very well-prepared loam soil that has had plenty of organic matter added to it and is well-draining, you might find that your kale seeds will start to germinate sooner than 5 days.
Climatic conditions can also influence how long it takes for your seeds to germinate. The ideal conditions that favor quick seed germination are warm soil and a temperature above 45 degrees Fahrenheit (7 degrees Celsius).
When the seeds germinate, you’ll see two small seed leaves emerge from the soil. These are called cotyledons and don’t resemble the true leaves of the plant. These seed leaves will use up the energy within the seed to keep the little plant alive as well as carry out some photosynthesis using the energy from the sun.
During this time, you want to keep your little kale seedlings well watered as they need plenty of moisture to develop strong roots. Take care, though, that any excess water can drain away quickly because you don’t want your tiny seedlings to become waterlogged.
Emergence Of The True Leaves
Within around two weeks from seed sowing, you’ll see the first true leaves starting to grow. These leaves will now look like miniature kale leaves. They’ll continue to grow larger as the plant starts to produce more and more leaves.
New leaves are produced on the inner part of the plant, while the outer leaves get much larger. After around 60 days from when you planted the seeds, your healthy kale plants should have more than ten leaves.
There will be smaller leaves in the center of the plant and large leaves around the outside. At this stage, you can start to harvest some of the outer leaves to use. It’s important that you only harvest the outer leaves so that the plant can continue to produce many more new leaves from the center of the plant.
By continually harvesting the outer leaves, your kale plants will generally continue to produce more and more leaves during their first year of growth, especially if you are in USDA zones 7 and above.
In colder regions, your kale may stop producing many new leaves during the winter, but you can still continue to harvest the outer leaves right throughout the season. In really cold areas, you might even notice some die back of the leaves. However, the roots will still be alive under the ground.
If you do live in an area that suffers from really cold winters, you can protect your kale by covering the soil around the plant with a thick layer of mulch to insulate it a little. You can even protect your kale plants from heavy snow by placing a cold frame or polytunnel over the plants.
The Reproduction Cycle
Because most kale varieties are biennial, the plants put all their energy into growing leaves in their first year of growth and then switch to reproduction in the second year.
This means that once your kale plants have gone through a winter season when the weather starts to get warmer, they’ll switch to producing flowers and eventually seeds.
During spring, kale plants will sprout tall stalks that have masses of bright yellow flowers. These flowers attract a variety of pollinators such as bees, and so they’re quite beneficial for your garden.
However, this reproduction phase will cause the leaves of the plant to become a little tougher, and excessive heat will also cause the leaves to become bitter.
You can still harvest some of these leaves, but they’re better used in your cooking and generally not suitable for eating raw. You’ll also find that the flower buds are edible, especially in varieties of Siberian and Russian kale.
As the plant continues to grow, eventually, you’ll see the growth of long, thin, green seed pods. The seeds inside these pods will complete the life cycle of each kale plant. If you want to harvest the seeds for growing more kale, wait until the seed pods are dry, and they’ll open easily to reveal the tiny seeds within.
Are There Any Perennial Varieties Of Kale?
For gardeners who live in USDA zones 6 and above, there are a couple of perennial varieties of kale that you might like to consider growing.
- Perpetual Kale (Brassicaoleracea var. ramosa)
Also commonly labeled ‘Daubenton’, this variety of kale doesn’t produce seeds but is propagated via root cuttings. The plant will continue to grow for around 5 to 6 years and can be harvested continually during this time. The leaves are mild in flavor and a little nutty.
- Walking Stick Kale (Brassicaoleracea var. longata)
This variety is also commonly known as Jersey cabbage or tree cabbage and is native to the Channel Islands. It produces long stalks that were dried and harvested to make walking sticks. In fact, the plant can produce stalks as tall as 20 feet under ideal conditions. The leaves can be harvested and cooked after removing the mid-vein, which is quite tough. They have a nutty, sweet flavor.