Your Guide to Growing Kale Indoors

Last Updated on October 10, 2020

Kale is a biennial green and purple vegetable and a member of the brassica family. It’s a nutritious veggie, with lots of nutrients—vitamins C, A, and K, magnesium, potassium, calcium, and fiber.

OK, so we know it’s super healthy, but did you know that growing kale indoors is easy and so much fun! Plus, you’ll have access to a fresh salad topping all year long.

To plant kale indoors, you need kale seeds, pots, growing mix and water. You should prepare the containers, plant the seeds, and cover them with soil. You can transplant the young kales in bigger pots after almost a week, but you should locate them with enough sunlight and water them regularly.

There’s a bit more to it than that, though, so let’s get stuck in… 

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Can Kale Be Grown Indoors?

It’s easy to grow a kale plant indoors, and it doesn’t require special equipment, especially if you’re a beginner.

Here’s the equipment you need:

  • Seed trays or small containers: Buy seed trays for germination or use small containers. Keep in mind that they should have drainage holes
  • Plant containers or pots: Choose containers that are at least 12 inches wide and tall for growing kale indoors—unless, of course, you’re planting dwarf kales
  • Seeds: Purchase the kale seeds of your favorite kale family member—more on this below. 
  • Soil: Use well-draining potting soil or soilless growing mix designed for growing vegetables indoors, which is better because it won’t clump up. Kale prefers acidic soil pH. 
  • Water: Use filtered water and preferably a spray bottle. 
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How to Grow Kale Indoors—Five Easy Steps!

Growing kale plants isn’t very complicated. Here’s what you need to know: 

1. Prepare the Soil and Seeds

  1. After deciding on how many kale plants you want to grow, count out two or three seeds for each one.
  2. Put all the seeds in a little container full of water and soak for approximately 6 hours.
  3. Fill each tray part or container with 3–4 inches of the growing mix.
  4. Moisten the mix with a bit of water.

2. Plant the Kale Seeds

  1. Sprinkle two or three kale seeds in each of your seed containers. If you’re using one big container, remember to give them space and sow them about 4 inches apart.
  2. Sprinkle a thin layer of soil or growing mix over them until they’re 0.5 inches deep.
  3. Mist or sprinkle enough water to keep the seeds wet without overflowing. 

Also, consider sowing a couple of seeds every few weeks so that not all your plants mature at once. 

3. Take Care of the Seeds 

At this point, the seeds don’t have a reliable root system for getting the water they need. So, you’ll have to keep the soil moist enough for the roots to grow easily.

Kale seeds don’t need sunlight for germination, but keep them in a warm place and keep their soil moisturized. Covering your containers or seed tray with a plastic bag will help create this environment.

4. Transplant: How to Transplant Kale

Transplanting your seedlings will speed up their growth:

  1. Prepare your containers with 12 to 16-inch-wide and equally tall drainage holes for each kale plant. If you want to grow more than one plant in a container, be sure to plant them 16 inches apart for air circulation and space to spread. 
  2. Fill your containers with the growing mix or potting soil until they’re ¾ full.
  3. Remove each seedling very gently from their containers without damaging their roots.
  4. Dig small holes for every seedling, and place their roots in them and entirely cover their roots with the mix.
  5. Sprinkle or spray water on them to keep them moist. Be careful not to overwater them and knock them over. Don’t miss a watering because they can dry out fast.

5. Harvest: How to Harvest Kale

To harvest kale: 

  1. It’s best to start with the oldest and lowest leaves.
  2. Pick them near the base of the plant, one by one.
  3. Keep the central and new leaves.
  4. Do this every week or as needed.

When To Harvest Kale

Kale can mature in about 30–40 days if transplanted; otherwise, you need 55–65 days. When the leaves grow as big as your hands, it’s time for harvest.

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The Best Time to Grow Kale Plants

These are the best times to get started with kale planting: 

  • Spring: You can start growing kale indoors in early spring, 4–6 weeks before the last frost to harvest in summer or at the beginning of fall.
  • Summer: Grow kale indoors at the end of summer, 6–8 weeks before the first frost, so that you can harvest in the fall or winter.
  • Fall: If you have a mild winter coming, start planting kale in the fall for a winter harvest.

Taking Care of Kale

You need to provide enough light and water and proper soil and fertilizer for your kale plant. You should also keep the temperature just right and protect them against pests.

How Often to Water Kale

Kale needs consistent watering and moist soil to grow sweet and crisp leaves. If the soil dries out, you’ll get tough and bitter leaves.

Water your kale plants at their base and stop if water starts to overflow to avoid harming the roots. Aim for approximately 1.5 inches each week. 

Soil and Fertilizer

Kale plant prefers rich and acidic soil, with a pH between 6.0 to 7.5, and the right amount of nitrogen in the soil helps grow healthy leaves.

A balanced 10-10-10 fertilizer is best for growing kale, meaning it has 10% nitrogen, 10% potassium and 10% phosphate.

Once your plant is established, it benefits from the right amount of fertilizer, as well. Use organic fertilizers, like aged-compost, fish emulsion or worm castings, every six or seven weeks throughout the season. Remember to apply just a thin layer. 

Temperature and Light: Does Kale Need Sunlight To Grow?

Kale grows best when it receives abundant sunlight. However, you must protect it against scorching hot weather. Once your plant begins to grow, make sure it gets 4–6 hours of sunlight every day. You can keep it next to south-facing windows to help with this.

It prefers morning sun than afternoon sun, as too much heat can damage or scorch the leaves. 

If you live in warm regions, where the temperature exceeds 70°F, provide partial shade and enough water. 

Kale is a cool-loving plant. It will taste sweeter if it’s exposed to a couple of frosts!

But, you can damage it if you don’t protect it against heavy snow or cold temperatures. The optimal temperature for growing kale indoors is 60–65°F, but the plants can germinate at 45°F to 85°F

Common Pests and Diseases

Like other cabbage family members, kale attracts pests, like aphids, cabbage worms, cabbage loopers, and flea beetles. It’s also susceptible to rot diseases, like black rot and clubroot. 

To protect your plants against aphids, release ladybugs or Aphelinus abdominalis—a parasitic wasp. You can also kill the aphids by spraying neem oil on your plants.

If flea beetles eat your plants, use diatomaceous earth (DE), spinosad, or products containing pyrethrin.

If you see any cabbage worms on your crops, simply pick them and their eggs up, then put them in soapy water. You can also use bacterial insecticide sprays. 

You can also use companion plants to protect kale against pests. 

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What Grows Well With Kale?

Vegetables 

Kale’s companion vegetables are beans, beets, peas, tomatoes, lima beans, hot peppers, potatoes, cucumbers and carrots. 

Peas and beans are good companions because they add the nitrogen kale needs to the soil.

Hot peppers repel pests as well, while sweet potatoes and lima beans are insectary plants, and beets are light feeders, which means they don’t need much mineral nutrients to grow. 

Avoid planting kale with brassicas or where cabbage family crops were recently grown. 

Alliums 

Chives, garlic, and onions are repellants and can keep moths, mites, flea beetles, and aphids away from kale. 

Herbs

Herbs or insectary plants can attract beneficial predatory insects. Dill, cilantro, catnip, sage, thyme, mint and lemongrass are the ones you want around your kale.

Specifically, cilantro, dill, mint and catnip are light feeders, and they also attract beneficial insects.

A study found that rosemary, dill, mint, chamomile, sage, thyme and nasturtiums can protect brassica crops, like kale, against pests.

Frequently Asked Questions About Growing Kale Indoors 

How Long Does It Take To Grow Baby Kale?

Expect to have baby kale in about 25 days. It takes about 10 days for the plants to germinate, and your seeds will sprout a few days after that. Once your kale is established, you have to take good care of it before you see results. 

How Long Does It Take for Kale To Grow?

It will take kale roughly 4–6 weeks to get about 9 inches tall and develop three or four leaves, which is the perfect time for transplanting them.

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Conclusion

Growing kale indoors is easy.

You just have to provide the right space, proper light and water, rich soil and suitable fertilizer. 

Keep an eye for pests and diseases and harvest your kale plants when it’s time. This way, you’ll have access to fresh and nutritious kale all year long!

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