21 Must-Know Tips For Growing Kale Indoors
Kale has become an increasingly popular choice of leafy greens in the last decade. And why not? This nutrient-dense veggie pairs well with almost every meal. Sandwiches, pizza, pasta, soups, fresh salads, smoothies – you name it – you can integrate kale into all of them. And kale chips are a delicious and healthy snack.
And while it’s fun to eat kale throughout the year, it doesn’t grow well outdoors in many places. It’s a cool-season vegetable that can typically handle some frost in its adult form, but areas with more extreme cold weather temperatures aren’t always ideal for growing kale.
Instead of worrying about the time of year to plant kale, skip the grocery store and grow your own inside! You don’t have to worry about planting after the last frost. And if you live in a city or somewhere with less outdoor gardening space, growing kale indoors can be the perfect solution. These plants are surprisingly easy to grow in an indoor garden, they can be a great way to supplement your grocery budget, and their many-shaded leaves can be the perfect accent for any home.
Let’s dive into the exciting world of growing kale indoors.
Can Kale Be Grown Indoors?
While kale is traditionally grown outside, it’s possible – and even easy – to grow kale indoors all year-round. With proper lighting, soil, and nutrients, you can grow mature kale, baby kale, and even kale microgreens in a small indoor space.
Growing Kale Indoors (In A Nutshell)
Here are all the things you’ll need to start growing kale indoors. We’ll break down these individually in the article. But here are the basics:
- kale seeds – common varieties listed below
- grow lights or another light source that gives kale full light during the day
- potting for seeds
- planting medium (potting soil/potting mix works fine for most situations)
What Is Kale?
This green superfood is in the cole crop family of the species Brassica oleracea, and shares some similarities with non-heading cabbage, swiss chard. A decade ago, kale was mainly grown in the U.S. as a garnish on dishes, but this changed once we started to learn the health benefits of actually eating the leafy vegetable.
What Does Kale Look Like?
There are several varieties of kale – each with specific distinguishing features and sizes. One of the most common types sold in American grocery stores is called Common Curly Kale (or just curly kale), which has light green spines (the stem through the middle of the leaf), and ribs (steps that run through the leaves). Check out these most common types of kale:
- Common Curly Kale – This is a typical American variety with a range of bluish-green color in the leaves – with the edges of the leaves frilling at the end.
- Lacinato Kale (includes Dinosaur Kale and Tuscan Kale) – This kale has longer, darker leaves (unlike most common varieties).
- Thomas Jefferson grew this type of kale in his garden.
- Dwarf blue curled – Dwarf varieties are often more manageable than other, larger varieties, which can grow up to two feet when they’re mature. Dwarf varieties are recommended if you’re planning to grow your kale on a windowsill or balcony.
- Red Russian – This variety of kale is known for being semi-sweet and tasting good raw.
Here’s a breakdown of types of kale and links to buy seeds.
Growing Kale Indoors From Seed
When planting kale seeds, you must sow seeds from 1/4 to 1/2 each deep, according to the Old Farmer’s Almanac. Typically, you should use a seed tray for germination that has proper drainage. For the growing medium, use either a growing mixture designed for vegetables or a soilless medium that includes perlite or vermiculite.
Here are some of our favorite types of potting mixes available from Amazon:
- Black Gold All Organic Potting Mix
- Miracle-Gro Potting Mix
- FoxFarm Happy Frog Nutrient Rich Potting Mix
When you sow seeds, only put a few of each seed in each container and cover them with about 1/2″ inch of the growing medium you’re using.
It’s important to keep your seeds warm during this period – close to around 70 degrees F. It can technically germinate as low as 48 degrees F, but lower temperatures will slow down the speed of germination.
If you’re worried about keeping your kale seeds warm enough, consider using a Seedling Heat Mat. They’re affordable and useful for controlling the temperature.
If you’re planning to transplant your kale from indoors to outdoors, the best time to sow your seeds is in early spring or mid-summer, which will ensure a late summer or winter harvest. Another option is to start about one to one and a half months before the last frost then move the plants outside when the weather warms.
For the last 4 or 5 months I've been growing lettuce, spinach, and kale indoors. Today I harvested the last of it so I can start more. I think I'll stagger plantings to see if I can keep a supply going all the time. I've loved indoor #gardening a lot. #food pic.twitter.com/Ip7FOtAQ8t— Shelley Woodard (@ShelleyW2009) February 20, 2021
We recommend that you thin your kale about ten days after planting, which will help the healthiest sprouts to thrive. For all the plant lovers out there, this may be a difficult step, but it improves the health of your plant and overall harvest.
Thin the kale seedlings so they are between 8 and 12 inches apart. Kale typically takes five to eight days to germinate from a seed. This can sometimes happen faster if you’re using a grow light that allows for more hours of sunlight.
If you germinated your kale seeds in a tray, you can transplant them to larger pots after about two weeks.
How Many Days Does It Take To Grow Kale
Mature kale is ready to harvest in about 60 days, depending on the variety. You should wait until the leaves reach about seven inches before harvesting. If you’re interested in growing baby kale, which has a slew of benefits, you can harvest in as little as 25 days.
A quality potting soil that’s high in organic matter will work for kale. It needs to be a potting mix that drains well and typically has a pH of 6.0-7.9. Some potting soil options that work well for kale include the following: Gardener’s Potting Mix, Miracle Grow All Purpose Potting Mix, and The Sill Organic Potting Mix.
If you’re planning on growing the kale in a hydroponic garden, you would be better using a soilless growing medium such as peat moss. This would help keep the soil from getting into the water pump of the hydroponic system. Whatever growing medium you choose, you’ll be harvesting the leaves, so your indoor kale plants must have access to a high amount of nitrogen.
Stay clear of using soil from your garden, which could lack proper nutrition or contain diseases that your kale will be susceptible to.
You must keep the soil moist when growing kale, as it’s a fast grower. It should never dry out fully.
Growing Kale In Containers Indoors
Depending on the variety of kale you choose, the space needed indoors may vary. But even smaller varieties, such as Dwarf Blue Curled varieties, need a 12″ container per plant. This is quite different from other veggies, such as carrots, which could grow several plants at once in the same 12″ space.
Does Kale Need Direct Sunlight
When growing kale indoors, it should still receive full sun during the day – typically six hours or more, but it can also grow with partial shade, which is four to six hours during the day. One of the best places to get the needed light for your kale plants is in a south-facing window.
Don’t have a sunny window with access to six hours of light? No problem. Another option for a light source is to get a grow light. Grow lights can help you supplement your plants with natural light during the day. This artificial light can be an excellent way to give the kale plant the much-needed sun it needs. In most cases, your grow light should be around six inches above the top of the plant, but move it further away if you notice scorching.
Here are some basic grow lights you can use for kale:
Check out the best small grow light options we recommend.
Kale is a cool-season leafy green, so you want to keep it in cool temperatures . The preferred soil temperature for growing kale is approximately 60-65 degrees. That said, a bit of frost can sweeten the taste of kale, so you may want to stick your plants outside if the weather allows.
While cool weather is usually better, too much cold can also be dangerous. If you’re growing kale in a shed or anywhere else with dangerously cold temperatures, here are some grow mat options to help regulate the temperature.
You want to make sure your soil stays moist but not overly damp. For most growers, this amounts to 1-1.5 inches of water per week. The soil should be noticeably wet – but there should not be standing water in the pot. If you start to see your kale’s leaves turning yellow, it is likely a sign that you’re overwatering it.
Best Fertilizer For Kale
Any balanced fertilizer (like a 10-10-10) will work well for kale, especially a water-soluble fertilizer that you mix with one gallon of water. Typically, you should fertilize your kale every seven to ten days. Here are some top fertilizer options for growing kale indoors.
- Dr. Earth Home Grown Tomato, Vegetable, and Herb Fertilizer
- Osmocote Flower and Vegetable Smart-Release Plant Food
- Miracle-Gro All Purpose Plant Food
How to Harvest Kale
You can harvest kale periodically when the outermost leaves are about the size of your hand. Start by taking these mature leaves off the plant (the more tender leaves are best), which allows the younger leaves to continue growing. The mature kale plant leaves will last up to 14 days if you place them in the refrigerator in a sealed plastic bag.
Growing Kale Hydroponically
If you’re growing kale indoors, it may make sense for you to raise these greens hydroponically. This means that you’re not growing with soil and – instead – are growing the kale using nutrient-rich water distributed along the roots and growing medium. Most countertop hydroponic systems can quickly grow kale and other greens. AeroGarden, Gardyn, iHarvest, and Rise Gardens both provide excellent options for growing kale indoors. Check out the best hydroponics systems for growing kale.
How To Grow Kale Microgreens
Microgreens are young edible greens produced from a vegetable or herb. Research suggests that young kale microgreens are an excellent source of potassium, calcium, and antioxidants.
For kale microgreens, you’ll start with a container that you fill to the brim with rich soil, spray with water to make it moist, and then distribute seeds evenly across the top of the soil. You want to cover the entire surface with the kale seeds. Water the seeds lightly, and then cover them up with aluminum foil to keep out all the light.
After 3-5 days, your kale seeds should have germinated and are ready for sunlight – or you can use an artificial light. You’ll want to continue watering them regularly, but not enough to develop mold.
You should be ready to harvest your kale microgreens just about ten days after planting them. You can use a paring knife to harvest these microgreens.
What Is Kale Good For?
This supreme leafy green has been called a superfood. And there’s a lot to be said for it. Kale has antioxidants, calcium, vitamin K, vitamin C, vitamin A (a single cup will give you 200% of your daily requirement), fiber, manganese, copper, potassium, magnesium, vitamin B6, and more.
Here is the full list of nutrients in kale.
Benefits of Growing Kale Indoors
Whether you don’t have the space or you’re just craving a kale smoothie during the dead of winter, growing kale indoors is an ideal option. And many varieties of kale look visually appealing, so they can even work as a houseplant. Not only this, but having kale inside means, you can easily access your harvests without taking a trip to the garden.
Kale Pests To Look Out For
One of the benefits of growing indoors is that your plants are protected from most pests. But if a window or a door is ever open, an infestation is still possible. Here are some of the most common pests known to hurt kale:
- Harlequin Bug
- Imported Cabbage Worm
- Flea Beetles
For help with pests on your kale, start here.
The Big Idea
Fresh kale can be grown in the comfort of your home. It’s an easy plant that you can raise without much time or effort, and it will be sure to provide you and your family with highly nutritious leafy greens throughout the year. Start growing kale today with these easy steps. So whip out your green thumb and get started today!