Kale is one of the most rewarding crops for home gardeners. It is hardy, versatile, and packed with vitamins. Whether you have a sprawling backyard or a few pots on a balcony, learning how to plant kale from seed is a straightforward process. This guide provides a step-by-step approach to ensuring your kale crop thrives from the moment the seed hits the soil to the day you harvest your first leaves.
Understanding Kale Varieties
Before you start planting, it is helpful to choose a variety that fits your culinary needs and climate. Lacinato kale, also known as dinosaur kale, features dark blue-green, bumpy leaves and a milder flavor. Curly kale is the classic grocery store variety with ruffled edges and a sturdy texture. Red Russian kale is prized for its tender, oak-like leaves and purple veins, making it excellent for salads. All these varieties follow similar planting principles, but their maturity dates and cold tolerance may vary slightly.
When to Plant Kale Seeds
Kale is a cool-season crop. It can withstand light frosts and actually tastes sweeter after a touch of cold weather. You generally have two windows for planting.
Spring Planting
For a summer harvest, start seeds indoors about 6 weeks before the last frost date. If you prefer direct sowing, wait until the soil can be worked and is at least 40°F.
Fall Planting
For a late autumn or winter harvest, sow seeds directly into the garden about 6 to 8 weeks before the first expected fall frost. In many regions, kale will continue to grow through the winter if provided with minimal protection.
Preparing the Growing Site
Kale thrives in full sun but can tolerate partial shade. If you live in a particularly hot climate, afternoon shade can prevent the plants from wilting.
Soil Quality
The ideal soil for kale is well-draining and rich in organic matter. Use a garden fork to loosen the soil to a depth of about 8 to 12 inches. Mix in a generous amount of compost or well-rotted manure to provide the nitrogen kale needs for leafy growth.
Soil pH
Kale prefers a soil pH between 6.0 and 7.5. If your soil is too acidic, you can add lime. If it is too alkaline, sulfur or peat moss can help balance it. A simple soil test kit from a garden center can help you determine your baseline.
Planting Kale Seeds Indoors
Starting seeds indoors gives you a head start on the growing season and protects young plants from unpredictable early spring weather.
- Use Seed Trays: Fill seed trays or small pots with a high-quality seed-starting mix. Avoid using garden soil, as it is too heavy for delicate seedlings.
- Sowing Depth: Plant seeds about 1/4 to 1/2 inch deep. Place two seeds per cell to ensure at least one germinates.
- Moisture and Warmth: Mist the soil so it is damp but not soggy. Place the trays in a warm spot or on a heat mat. Kale seeds usually germinate within 5 to 10 days at temperatures around 70°F.
- Light Requirements: Once the sprouts appear, move them to a very bright windowsill or under grow lights. Keep the lights about 2 inches above the tops of the plants to prevent them from becoming “leggy.”
- Hardening Off: About a week before transplanting, start moving your seedlings outdoors for a few hours each day. Gradually increase their time outside to acclimate them to the wind and sun.
Direct Sowing Kale Seeds Outdoors
If you prefer to skip the indoor trays, kale is easy to sow directly into the garden bed.
- Create Furrows: Use your finger or a tool to create shallow rows about 18 to 24 inches apart.
- Space the Seeds: Drop seeds every 3 inches along the row. You will thin them later.
- Cover and Water: Lightly cover the seeds with soil and firm it down with your hand. Water gently using a mist setting on your hose to avoid washing the seeds away.
- Thinning: When the seedlings reach about 3 inches tall, thin them so that the remaining plants are 12 to 18 inches apart. You can eat the thinned seedlings as microgreens.
Caring for Growing Kale
Once your kale is established, it requires consistent care to produce the best quality leaves.
Watering
Kale needs consistent moisture to keep its leaves crisp and sweet. Aim for about 1 to 1.5 inches of water per week. Mulching around the base of the plants with straw or shredded leaves helps retain soil moisture and keeps the roots cool.
Fertilizing
If you prepared your soil with plenty of compost, you might not need additional fertilizer. However, if growth seems slow, you can apply a balanced liquid fertilizer or a nitrogen-rich side-dressing every 4 weeks.
Weed Control
Keep the area around your kale free of weeds. Weeds compete for nutrients and water. Because kale has shallow roots, be careful when hoeing near the base of the plants. Hand-pulling weeds is often the safest method.
Managing Pests and Diseases
Kale belongs to the brassica family, which means it can attract certain pests.
- Cabbage Worms: These small green caterpillars eat large holes in the leaves. You can pick them off by hand or use an organic spray like Bacillus thuringiensis (Bt).
- Aphids: These tiny insects often cluster on the undersides of leaves. Wash them off with a strong stream of water or use insecticidal soap.
- Clubroot: This is a soil-borne fungus that causes stunted growth. To prevent this, rotate your crops and avoid planting kale in the same spot where broccoli or cabbage grew the previous year.
Harvesting Your Kale
You can begin harvesting kale as soon as the leaves are about the size of your hand. This usually happens 50 to 65 days after planting, depending on the variety.
- Harvest from the Bottom: Always pick the lowest, outermost leaves first. This allows the center of the plant to keep growing and producing new foliage.
- Leave the Crown: Avoid picking the very top leaves or the “terminal bud.” Doing so can stop the plant’s growth entirely.
- Store Properly: Kale keeps well in the refrigerator. Place the unwashed leaves in a perforated plastic bag in the crisper drawer. It should stay fresh for up to a week.
Frequently Asked Questions
Can I grow kale in containers?
Yes, kale grows very well in containers. Ensure your pot is at least 12 inches deep and has drainage holes. Use a high-quality potting mix rather than garden soil to ensure proper aeration and drainage.
How much sun does kale really need?
While kale prefers full sun (6 or more hours per day), it is one of the few vegetables that can tolerate partial shade. In hot regions, partial shade is actually beneficial as it prevents the plant from bolting or becoming overly bitter.
Why is my kale tasting bitter?
Bitterness in kale is often caused by heat stress or lack of water. If the weather is too hot, the plant produces defensive compounds that affect flavor. Conversely, cold temperatures and frost convert starches into sugars, making the leaves much sweeter.
Does kale grow back after you pick it?
Yes, kale is a “cut and come again” vegetable. As long as you leave the central growing point intact and harvest only the outer leaves, the plant will continue to produce new growth for several months.
Is it better to start kale seeds indoors or outdoors?
Both methods work well. Starting seeds indoors is better for an early spring crop to avoid late freezes. Direct sowing is often easier for fall crops when the soil is already warm and the air is beginning to cool.