How to Grow Kale: Planting, Growing, Harvesting
Kale is a low-maintenance, cool-season crop belonging to the cabbage family. Low in calories but packed full of nutrients and vitamins, it can be eaten raw or lightly cooked. It’s not too pretentious about the soil it grows in, it doesn’t mind freezing temperatures, and it’s so versatile you can even use it for ornamental purposes.
In our growing guide for kale, we’ll take a look at how to plant, grow, and harvest this wonderful vegetable, and share some top tips on how to grow it in containers — both indoors and in your vegetable garden.
Kale Varieties You Can Grow
Kale is a non-heading cultivar of Brassica oleracea, the same plant that gave us cabbage, cauliflower, kohlrabi, and broccoli. And, thanks to selective breeding, kale is now available in a wide range of cultivars of its own, each with a unique taste, texture, and leaf color.
Here are 5 kale varieties you can grow in your garden.
- Curly kale: The best-known type, this is the kind you’ll usually find in supermarkets. The ruffled, frilly kale leaves have a tender texture when young, with a nutty sweetness and slightly earthy aroma.
- Tuscan kale: Also known as Cavolo Nero (black cabbage) and dinosaur kale, this variety produces large, slender, dark blue green leaves. Unlike curly kale, the leaves don’t have ruffled edges, but they have a noticeable bumpy texture and can be a bit tough, making them a great addition to stews and soups.
- Red Russian kale: Alternatively called plain-leaf, this heirloom kale cultivar has flat, bright green leaves, with distinctive red or purple stems and leaf veins. It’s one of the tastiest varieties, and even fully grown leaves have a pleasant sweetness and tender texture.
- Gai lan: Commonly called Chinese kale, this variety produces spinach-like leaves and long, tender stems similar to broccolini. It has a mustardy bite, and it’s usually sold in supermarkets with the edible yellow flowers included.
- Ornamental kale: A bouquet of curly, dark green, and pink or white leaves, this is a common sight in ornamental garden beds and flower arrangements. It’s perfectly edible, though perhaps not as tasty as other kale varieties.
When Is the Best Time to Plant Kale?
Kale is a cold-weather crop that grows best in temperatures between 60°F and 75°F (15°C to 24°C). It is remarkably frost-hardy but very sensitive to heat. It becomes susceptible to bolting in temperatures above 75°F and will struggle to grow in hot climates, or in the height of summer.
Spring planted kale can be sown directly in the garden soil as long as soil temperatures are above 40°F (4°C). Fall planted kale can be sown 3 months before the first fall frost. For winter harvests, you can grow kale from seed under row covers in late fall. However, this hardy vegetable won’t mind a light frost and even a bit of snow. As long as temperatures don’t drop below 25°F (-4°C), you can keep it outdoors until late January.
When to plant kale depends entirely on your growing zone. As a rule of thumb, you can sow kale outdoors in early spring, 3 to 5 weeks before the last frost, then plant a second crop in early fall. To make planning your vegetable garden easier, check out our planting calendar, and see which months work best in your hardiness zone.
Where Should You Plant Kale?
The ideal place for planting kale is a part of your garden that gets full sun. Kale plants can tolerate partial shade, however, they will grow slower. On the plus side, partial shade can work in your favor if you’re growing kale in summer or in warm climates. This will keep the plants cool and prevent kale from bolting.
You can plant kale directly in the garden soil, in raised beds, straw bales, and even in containers. Kale plants can also grow indoors, but for best results, they need a room that receives at least 6 hours of direct sunlight per day. We’ll take a closer look at how to grow kale indoors later in our growing guide.
How to Plant and Grow Kale
Kale is one of the most beginner-friendly vegetables you can grow. It takes 2 months from seed to harvest, it tolerates frost and is rarely bothered by pests. You only need three things to grow delicious kale in your garden: full sun, nutrient-rich soil, and consistent watering.
Let’s take a closer look at what you need to know about how to grow kale and what you need to do to get started.
Prepare the Soil
Kale grows best in a well-draining, slightly acidic soil that’s rich in organic matter. Start digging the soil to a depth of one foot (30 cm) one month before planting, and work in plenty of composted manure. You don’t need to worry too much about the soil pH for growing kale. This vegetable can tolerate anything between 6.0 and 7.5.
Sow Kale Seeds
You can grow kale from seed by either planting it directly in the garden soil or starting it indoors. The optimal soil temperature for germinating kale seeds is between 60°F and 65°F (15°C to 18°C), but the seeds will sprout in temperatures as low as 40°F (4°C).
For direct sowing, plant kale seeds ½ an inch deep (1.2 cm) and 20 inches apart (50 cm). Space your rows about 30 inches apart (75 cm), to give your plants plenty of space to grow. Cover the seeds with a thin layer of soil and water them well. Kale seeds germinate very quickly, and you’ll start seeing tiny leaves in about 5 to 10 days.
If you’re planning to transplant, sow the seeds in compostable seedling pots. Fill them with an organic potting mix, and plant one kale seed per pot. Keep the pots in a warm, sunny room, and keep the soil moist but not soaked.
Transplanting Kale Seedlings
You can transplant kale seedlings outdoors when they have at least two pairs of true leaves. The young plants can survive a light frost, but for best results, wait a couple of weeks after the last frost for the ground to thaw.
Transplant the young seedlings about 18 to 20 inches apart. Handle the plants carefully, to avoid damaging the stems and roots. If you’re using compostable seedling pots, simply dig a hole the size of the pot and plant it whole. Water your young kale plants well and monitor them for the next couple of weeks to make sure they become established.
Regular and consistent watering is the key to growing kale successfully. Aim to keep the soil moist but not soaked, and never allow it to dry out completely. If you’re not sure when to water your kale, test the soil with your finger. If the top 2 inches (5 cm) feel dry to the touch, give the plants a good soak.
Consistent moisture is essential, especially in warm weather. If kale is exposed to water stress, it will develop an unpleasant, bitter flavor, and its leaves can become tough and leathery.
Kale also benefits from regular mulching, which helps keep the soil cool and moist. Add a layer of straw, weed free hay, grass clippings, or finely ground leaves around the base of the plants.
Like all vegetables in the cabbage family, kale is a heavy feeder and needs regular fertilizer applications. A liquid fertilizer that’s rich in nitrogen is ideal. Always check the dosage instructions on the label and dilute if necessary.
If your soil has been amended with generous amounts of compost and manure before the spring sowing, you don’t need to give your kale plants any fertilizers. But if you’re planting a second crop in the same spot, it’s best to give your plants a nutrient boost using bone meal or liquid seaweed.
Kale will not tolerate competing with other plants for nutrients, so keep your garden beds free of weeds. Shallow, regular digging around the plants, using a garden hoe, will help keep the weeds at bay. Take care not to damage the kale roots. Mulching also helps suppress stubborn weeds.
When and How to Harvest Kale
You can start harvesting kale around 60 days after sowing, when the leaves are at least 6 inches (15 cm) long. But if you’re in a hurry, you can pick baby kale leaves after 30 days or so. Use the cut-and-come-again method to pick the outer leaves, then cut the entire plant when the weather gets too hot. For a fall crop, leave the plant in the ground and keep harvesting even if temperatures drop below freezing. A light frost will actually give the leaves a sweeter flavor.
Kale is a biennial plant, and in areas with mild winters, it will continue to grow the following spring. Keep harvesting the tender young leaves, then remove mature plants in early summer, before they get a chance to produce flowers.
You can eat kale raw, lightly cooked, or turned into juice. Eating raw is the best way to preserve its vitamins and minerals. However, it will retain most of its nutritional value if it’s steamed, sauteed, or stir fried. Kale chips are a healthier — some would argue tastier — alternative to potato chips, and are a great way to convince kids to eat their vegetables.
Unlike most leafy greens, kale is easier to store. Wrapped in paper towels and placed in a zip-lock bag, it can last in the crisper drawer of your fridge for up to 2 weeks. The thick kale leaves also keep their texture fairly well after freezing, especially if you lightly blanch them first.
Common Kale Pests
Kale is an incredibly tough plant that rarely suffers from any problems. Its thick leaves, with their slightly waxy coating and bitter taste, are unpalatable to most pests. Also, it’s less susceptible to clubroot, a fungal disease that often threatens Brassica crops.
However, it’s best to be vigilant. So let’s take a look at what pests and diseases you’ll need to keep an eye out for.
Common kale insect pests include cabbage worms, cabbage white butterflies, cabbage moths, and gray green cabbage aphids. Use row covers to protect your crops, remove badly infested leaves, and spray your plants with a mild insecticidal soap solution.
Common kale diseases include Alternaria leaf spot, black rot, downy mildew, and anthracnose. Plant your kale in full sun, water it regularly, but avoid overhead watering, especially in hot, humid weather.
Companion Planting With Kale
Some of the best companion plants for kale are legumes such as beans and peas. Their nitrogen-fixing roots will give kale a nutrient boost, and the tall plants will shade it in hot weather. Kale also grows well with vegetables such as peppers, tomatoes, onions, garlic, and leeks — another frost-hardy crop that will keep kale company during winter. Nasturtiums and herbs such as dill, cilantro, and thyme will help repel pests.
Kale is susceptible to the same pests and diseases as cabbage and other plants in the Brassica family. To minimize the risk of infestations, never plant cabbage and kale together, and avoid planting kale in a part of your garden that has been used for cabbage for the past 4 years.
How to Grow Kale in Containers
Kale is a fantastic vegetable for in ground gardens or a raised bed, but you can also grow it in containers. And, given the fact that kale plants don’t mind a light frost, you can start growing kale in containers any time you like, then move the pots outside in early spring.
Start with a large container — a minimum of 12 inches (30 cm) would be ideal — with drainage holes at the bottom. Fill it with a nutrient-rich, organic potting mix. Sow 2 – 3 seeds per pot, water them well, and keep the container in a sunny location. When the seedlings emerge, thin out the weaker ones, until you only have one kale plant per pot. Water and fertilize regularly, and get ready to harvest the tender leaves after a month.
Growing Kale Indoors
You can grow kale indoors in a sunny room, an enclosed balcony, or a conservatory. This vegetable is a great choice for growing during the colder months, and it’s a great way to ensure a winter harvest of fresh, nutritious greens.
The main thing you’ll need to pay attention to when growing kale indoors in containers is light. Kale needs a minimum of 6 hours of sun to thrive. If you don’t have a room where it can receive full sun, it’s definitely worth investing in grow lights.
Kale is one of the easiest plants in the cabbage family you can grow. It’s delicious and nutritious, hardy and resilient, and will provide you with a fresh source of vitamins well into winter, after you have harvested your other crops.
Now that you know how to grow kale, be sure to include it in your list of vegetables to grow every year.