I’ve started to grow kale indoors as a houseplant. I’ve already documented my love of this superfood that I plant outdoors in my raised beds. I eat so much kale, I like to have lots of plants on the go, so I always have fresh leaves to harvest. Growing plants in the house means I don’t have to go traipsing outside with a flashlight in the winter when I need to harvest some leaves in a pinch for a dinner recipe. Plus, kale is quite ornamental on its own or displayed on a shelf with other plants.
I do cover some kale plants with floating row cover to get me through the winter. Last year I was harvesting all through December, January, and February. But I’m quite taken with the notion of growing food plants as houseplants. It just seems so efficient and win-win to me. Plus, it’s a little bit of insurance in case something happens to my outdoor kale. (Some years the deer treat my raised bed gardens as an all-you-can-eat buffet.)
There are a few different ways to grow kale indoors. Jessica has written a very thorough guide to growing sprouts and microgreens. You can apply these tips to growing them from kale seeds. The tender young seedlings are perfect to use in sandwiches, stir fries, and rice bowls. You can also grow kale under grow lights for baby salad greens, or in a pot as a mature kale plant that you harvest from time to time.
Deciding which varieties of kale to grow
In my experience, you get more bang for your buck by growing curly kale into more mature plants. Those ruffled leaves are also very ornamental. But it’s fun to experiment with different varieties to taste the subtle differences in flavour. The leaves of lacinato kale are good to use as baby salad greens. Container varieties will remain more compact in pots.
Kale plants tend to grow smaller indoors, which actually might make the leaves a bit more palatable to those who aren’t a fan. Smaller leaves are sweeter.
Whichever types of kale you decide to grow, you may want to stagger your sowing so that plants mature at different times.
If you don’t want to go to the trouble of starting seeds, you may be able to purchase an established kale seedling at a local garden centre.
Grow kale indoors under lights
Before I start my seeds later in the winter, my grow light setup has lots of room to place other plants and experiments. If you have the space, kale and other salad greens are pretty quick and easy to grow. My grow lights are in my laundry room, but there are some compact countertop grow light systems that allow you to grow veggies right in your kitchen.
Growing kale under lights allows you to sow lots of seed that will grow into young seedlings for baby salad greens. Keep in mind you need quite a few plants to be able to fill your salad bowl!
Fill a seedling flat that has drainage holes with a potting mix formulated for growing vegetables. Scatter seeds about a half inch to one inch apart. Sprinkle about a quarter of an inch of soil overtop to cover the seeds.
For watering, some grow light setups have a wicking mat that waters plants from underneath. I use a mister to keep the soil moist. Whichever way you water, consistent moisture helps promote good seed germination. Using a watering can moves the seeds around too much and doesn’t distribute the water evenly.
If you’re growing individual plants that will be eventually transplanted outdoors or to a bigger pot indoors, you can use a plug tray, adding about two to three seeds per plug.
Grow kale indoors in a sunny windowsill or sunroom
If you don’t have a grow light setup, you can still plant kale seeds indoors. Find your sunniest window and choose a spot on the windowsill or a nearby shelf.
You might find that a tray with a humidity dome comes in handy for germination and consistent moisture. However you can plant seeds in a regular pot. I just recommend that you use one with a drainage hole. I see so many pots in garden centres that are beautiful, but don’t have holes. If I absolutely need that particular pot, I’ll plant whatever seeds or houseplant in a plastic pot with drainage holes, and then use the hole-less pot as a decorative cover. But I digress.
Fill your selected pot or dome with an organic potting mix formulated for growing veggies (as mentioned above). Sow your seeds, about a quarter of an inch deep. Use a mister to spray the soil and keep it moist. If there is a dome cover, remove it once you think all (or most of) the seeds have germinated.
If you’ve grown your seeds in a tray, you may want to transplant them to different pots as they mature. Either way you’ll need to thin them out. Wait until the young plants have four true leaves and are about eight to 10 inches tall before moving them. Use a chopstick to gently loosen the soil around the seedling and place the seedling in a new pot with fresh soil.
Caring for your kale “houseplants”
One thing I certainly don’t have to contend with when growing kale indoors is the dreaded cabbage moth and subsequent cabbage worms. I just need to make sure I water my plants regularly (I find I check them more often than ornamental houseplants). Once they’re past the germination stage and a regular watering can won’t wash the seeds or seedlings away, you can water kale plants with a watering can.
Set up a schedule for fertilizing your kale plants. They like lots of nitrogen to develop those leafy greens. Set up a monthly schedule and apply a dose of organic liquid plant food (according to the package directions). You can time this with a harvest to encourage new growth.
Harvesting indoor kale
With mature, standalone plants, it’s important to note that you should always pick the outer leaves. The inner, middle stem is where all the new growth occurs. Use herb scissors or snips to trim your kale.
If you have a tray of baby kale seedlings, harvest when they have grown to about four to five inches. As with a mature plant, try to harvest the outer leaves first like you would outdoors with cut-and-come-again salad greens. You don’t want to annihilate the entire plant (unless you don’t care if it grows back after you first harvest.