Kale is one of the easiest vegetables to grow, and it’s also one of the most productive. As a result, it’s an ideal vegetable for almost any home garden. Kale is from the same species of plant as other brassicas such as broccoli, cauliflower, cabbage, and Brussels sprouts – which, cumulatively, represent some of the healthiest vegetables to eat. It’s also one of the hardiest vegetables, as kale can withstand both heat and cold, although it prefers cool weather, and the harvest tastes best after the cool fall weather.
There are a few different types of kale – the most common types include lacinato kale (a.k.a. dino or black kale), curly leaf kale, red Russian kale, and crosses such as rainbow lacinato. They are all grown similarly, so the choice of variety is purely based on the gardener’s preference.
Kale can be direct-seeded into the garden or transplanted as seedlings. Given that the plants last a full year, we recommend starting them indoors in the spring if you have the space. The sooner they start producing in your garden, the more harvest you’ll get from them throughout the year.
To start kale indoors, aim for a soil temperature of a few degrees above room temperature for maximum germination levels. Plant the seeds into 1” cell trays using a good quality seed starter. Bury each seed 1-2mm below the surface and press down on the seed after covering to push out any air pockets. Fertilize the seedlings with a diluted all-purpose fertilizer once the first true leaves emerge. Transplant the seedlings outdoors once there are at least six true leaves on the seedlings - typically at about the 6-week mark. In terms of timing, transplant the seedlings outdoors anytime from mid-April onwards (for southern Ontario climates).
A good garden bed for your kale has well-drained, fertile soil. Ideally, select a place that will receive less hot, late-day sun – preferably where it will see mostly eastern/southeastern sunlight. Mix lots of nitrogen-heavy compost into the soil before transplanting the seedlings to improve both drainage and fertility at the same time.
Plant kale seedlings 12” apart within each row with a minimum of 24” between the rows to reduce competition for nutrients and to allow the kale leaves to size up. When transplanting kale seedlings, bury their stems approximately ¼” to get the roots deeper. Don’t transplant any deeper than ½” or there’s a chance that the stems could rot. While not essential, it can be beneficial to plant kale under a fine-mesh row cover to prevent pests such as aphids, flea beetles, cabbage moths, slugs, snails, and earwigs.
Keep the garden beds well-fertilized for kale plants as they are heavy-feeders. The ideal fertilizer or compost used in cabbage beds should be nitrogen-heavy to get as much foliage growth as possible. Alternatively, plant the kale in a spot in the garden that follows legumes. Adding calcium will make the leaves crisper.
Keep the kale plants beneath row cover until you begin to harvest them, after which point the plants will be able to withstand the pests, and it will be easier to keep the row cover off unless the plants are getting attacked by pests. Water the kale bed regularly, particularly on hot, sunny days, but never let the soil become water-logged as that will invite soil-borne diseases.
Pests and Diseases
Kale plants are susceptible to a wide array of pests, including aphids, cabbage moths (and therefore cabbage worms), clubroot, cutworms, earwigs, flea beetles, slugs, and snails. Mature plants can withstand most pests, but the damage will impact the harvest amount and appearance. To manage these pests, use preventative measures such as a fine-mesh row cover on top of the plants, dusting diatomaceous earth on top of the leaves, and a circle of diatomaceous earth around the plant stems. Each of these measures will prevent pests without affecting the harvest.
In addition, if any spot in the garden has experienced black rot or clubroot in the past, avoid planting any brassicas in that space for 3-4 years and aim to raise the soil pH level above 7.0.
Harvest kale plants frequently once the leaves size up. Harvest by either cutting full-sized leaves off at the stem with pruners or by twisting them off by hand. Never harvest more than one-quarter of each plant’s total foliage at a time or else you will weaken the plant and reduce future harvests.
Once you’ve harvested kale leaves, loosely wrap them in plastic and store them in the fridge for up to 3 weeks.