How to Grow Kale Indoors

Kale used to be called the peasant’s cabbage. Now, it’s more like a wealthy Hollywood superstar’s cabbage.

 

Growing Kale Indoors: Best Kale Varieties to Grow Inside

We hear you asking, "Can you grow kale indoors?" and our answer is, yes, you can grow kale indoors! There are many varieties of kale, but we recommend only those that are considered dwarf varieties to be grown indoors. Here are our top 4 recommended varieties of kale for your indoor growing:

 

Growing Kale Indoors: Best Setup for Kale Plants

If you want to start growing kale indoors, you’ll need:

Planter:

Ceramic Self-Watering Planter (preferred) or pot that is at least 12″ / 5 gal.

Soil:

Standard Potting Mix

Plant Food:

Balanced Blend. This should be equal parts nitrogen, phosphorus, and potassium (with NPK numbers like 10-10-10).

Grow Light:

A strong grow light that can give the equivalent of 5+ hours of direct sun [DLI of 15+ mol/m²/day].

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Can You Grow Kale Indoors? Preparing Your Planter & Watering Schedule for Kale

Yes, you can grow kale indoors. Kale plants do well in moist soil conditions. If the soil dries out completely, the roots will die back and it will be tough for the plant to recover. On the other hand, if the roots are exposed to standing water for too long, they can rot.

A Ceramic Self-Watering Planter filled with a standard potting mix self-regulates to keep the soil at consistent moisture for your plant to thrive (and no watering guesswork for you).

To set one up:

1. Fill up the planter with dry soil from the bag, gently tamping down the top.
2. Dump the soil into a large mixing bowl and add water until the soil is moist, but not sopping wet (about ½ Cup).
3. Mix in 1 tablespoon of the Balanced Blend Plant Food.

If you are using a regular pot instead, it should be a little bit bigger (at least 12″ / 5 gal) and will need drainage holes to prevent it from being over-watered. Let the top of the soil dry out between watering.

Starting Your Kale: Seed vs Propagate

New kale plants can be started from seed (preferred), propagated from an established plant, or purchased live at many garden centers. We like starting from seed the best because it’s quicker than propagating from a cutting, less expensive than using live starters, has tons of options, and there’s no way unexpected visitors (pests!) are riding along.

How to Plant Kale Seeds

Kale grows quickly from seed. Plant 2 sites in a 12″ / 5 gal container. In larger containers, space sites 6″ apart. For each site, press 2 seeds into the surface. Keep the soil warm (45-85°F, ideally 70°F). Sprouts typically appear in 5 days but can be as quick as 4 days or as long as 7 days depending on your conditions.

How to Transplant Kale

Live starter plants give you a little jump start on your first harvest. When you’re in a garden center, pick the bush center, pick the bushiest plant available (tall and lanky ones will be weak growers) and give it a good inspection for pests. Leaves should be dark green without holes, spots, or curled edges. A best practice is to actually “quarantine” your plant for about a week after bringing it home to make sure it’s free and clear of ride-on pests.

1. Remove some soil from its final planter – leaving enough space for the bottom of the seedling to be just higher than the soil surface.
2. Hold on to the base of the stem with one hand, and turn the pot over while gently pulling the seedling. Giving the pot a few squeezes can help dislodge it.
3. Place in its final container and fill around it with soil so that it’s tight, but not compacted.

Where to Grow Your Kale Plants

Like all edible plants, kale needs lots of light to grow and develop good flavor. Sunlight is excellent for plant growth (and free!), and you might be lucky enough to have a spot that gets the 5+ hours of direct sun they need. Even with a bright window, it’s unlikely that you’ll have enough natural light in the winter, so we recommend a grow light for anyone who wants a constant supply of flavorful produce. For an introduction to grow lights, head over to our post on grow lights for indoor gardeners. We’ve also got a buying guide for screw-in types, but to keep things simple in this guide, we’ll just provide directions for the 24W Screw in Bulb by Sansi, which we think is a good middle-of-the-road option.

How Bright Should Your Grow Light Be?

Kale plants need the equivalent of 5+ hours of direct sunlight [DLI of 15+ mol/m²/day] to grow their best. To provide an equivalent amount with a grow light, it needs to be pretty bright! The 24W Sansi bulb should be placed 6 inches away from the top of the plant. This will give your PPFD (the standard measure of brightness) of 500 μmol/m²/s.

How Many Hours Per Day Do Your Kale Plants Need Under a Grow Light?

Kale plants are what’s known as “day-neutral” and can grow under a range of daylight lengths. To ensure they get enough light, we recommend setting up a timer to leave it on for 10+ hours per day.

Kale Indoor Growing: Extend Your Harvest by Keeping the Temperatures Cool

Kale is known as a “cool weather crop.” If it senses warming temperatures, it will “bolt” – send up flowers and become bitter in the process. Where you plant them can affect the temperature – lower positions on a growing rack, ceramic planters, and hydroponics with air bubblers tend to run cooler. It’s best to grow kale indoors on a window except on windows that get really hot (like bay windows).

Kale Indoor Growing: Week 1-2 – Check for Sprouts

You could see seedlings in as little as 4 days (though 5 days is more typical). If it’s been 7 days and you still don’t have any sprouts, it’s likely that your setup is too cold.

Kale Indoor Growing: Week 3 – Thin Your Seedlings

Thin your planter to only have 1 seedling per site – leaving the largest plant. If you are using the recommended planter (at least 12″ / 5 gal) this will mean you’ve got 2 plants after thinning. By getting rid of the smaller seedlings, you’re allowing the biggest and strongest one to flourish by reducing its competition for water, food, and space.

If your seedlings are under 1 inch, stretching out, or folding over, it’s likely that they don’t have quite enough light.

Kale Indoor Growing: Week 5 – How to Prune Kale

You’ll notice how all the stems and leaves of kale grow from a single, central point (called radial growth). The plant puts out new leaves in the center and pushes old leaves outward, getting bigger and bushier over time. Pruning and harvesting are one-in-the-same with kale. Once the plant has at least 3 separate stems coming from the base, take one of the outside leaves and cut it close to the base (½” above is fine). It’s good to leave at least 2/3rds of the plant left to regrow.

Kale Indoor Growing: Month 3+ – How to Harvest Kale

Just as you did with your first prune, pick the outer leaves as needed, always leaving at least 1/3rd of the plant left to regenerate.

Kale Indoor Growing: Year 2+ – End of Life

Kale is a cool-season biennial crop – meaning it will keep producing for 2 years as long as you keep the temperatures from getting too warm. Eventually, it will form a small broccoli-like head – this means it’s time to take it down and start over.

Shop This Blog

The right supplies can take the guesswork out of caring for your plants – and turn care from a daily to weekly routine. Through our grow tests, we’ve found these products to produce the best indoor kale (and also have simple maintenance). Plants are adaptable and can grow in many different conditions, so they are by no means necessary if you already have other supplies.

Best Containers for Kale: Ceramic Self-Watering Planters

Plants thrive on consistent moisture but can suffer if they’re waterlogged. A semi-porous ceramic self-regulates ideal conditions. Our favorite is the COSWIP planter. Runner up is XS Self Watering Planter by Wet Pot.

Best Soil for Kale: Standard Potting Mix

Kale likes a rich and moist root zone – so you are best off with a standard potting mix – we like this Potting Mix by Rosy Soil.

Best Nutrients for Kale: Balanced Blend

Kale likes nutrients that are equal parts nitrogen, phosphorus, and potassium (with NPK numbers like 10-10-10). For a balanced blend, we recommend: Dr. Earth All Purpose.

Best Light for Kale: DIY or Soltech

There is a very small chance that you have the bright windows needed to grow these without a grow light. If you are looking for a higher-end option – we love the Aspect Light by Soltech. For a more affordable option, a DIY setup using a 24W Screw-in Bulb by Sansi with a Clamp Light and Timer works well too. Check out our complete guide on a DIY setup for less than $40 or our buying guide for screw-in bulbs.