How to Grow Kale: Complete Planting and Harvesting Guide

Understanding how to grow kale gives you access to nutrient-dense greens that are filled with vitamins A and C. Kale is a robust leafy green that can adapt to almost any climate and will grow in USDA growing zones 3 through 10. Kale is perfect for raised bed gardens or patio containers, making it one of the best crops to grow for gardeners of any experience level.

What makes kale special is its cold tolerance. I have harvested crisp leaves from plants that were covered in snow and withstood temperatures in the 20s (Fahrenheit). Frost makes the leaves sweet, explaining the transition from bitterness to a nutty flavor. To experience kale year-round, time planting for early spring or late summer when the soil is beginning to cool.

Space is less important than you may believe. A single plant in the garden provides around 5-7 pounds, while kale grown in a container still yields about 3-4 pounds, enough for your salad for a week. I also like to focus on loose soil (lose the nitrogen-rich soil) and have plenty of moisture surrounding my plants. Any time I see those outer edges of the plant get larger, I pick them - they ripen at around 8 inches long.

To learn how to grow kale, timing is essential. For USDA zones 3-10, you'll want to sow your seeds 3 to 5 weeks before the last spring frost, or 6 to 8 weeks before the first frost of fall. I've discovered that fall-sown crops will produce sweeter leaves after a light autumn frost. Alternatively, spring crops will thrive in fairly warm soil that is not likely to get too warm at all.

Soil preparation is a definitive factor in determining your harvest's success. For heavy clay soils (like mine), I mix in three parts compost to one part native dirt. This is how I've brought stubborn clay plots back to life! A loose, crumbly texture allows the roots to breathe. For you lunar aficionados, if you want to grow leafy vegetables, sow seeds during the waxing moon. For something you want stronger roots, sow during the waning moon.

To all you urban gardeners out there -- listen up! A balcony that has some afternoon shade mimics the conditions found in forest understories and this situation is ideal for planting kale. I have had luck growing Lacinato kale in fabric pots on a fire escape that faces north. You can even use reflective mulch--like aluminum foil-- to bounce light into shaded raised beds, tricking your plants into thinking they've been basking in sunlight.

You can go ahead and avoid planting on full moon days if you live in a part of the world that has trouble with pests, I know this because in my youth we lost an entire crop to cabbage moths. The way I work around this is to plant the seeds 2 days after the full moon and pest activity will be substantially lower. To completely bulletproof your vegetables, use row covers as well.

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Soil Thermometer

• Soil Temp Monitoring: Measure 4 inches deep at 8 AM for accuracy.
• Ideal Range: 45-75°F (7-24°C); below 40°F (4°C) delays germination.
• Clay Soil Fix: Mix 3 inches of compost to improve drainage.
• Seed Depth: ¼ inch for optimal moisture retention and sprouting.
• Probe Placement: Avoid direct sunlight or wet soil for readings.
• Calibration Check: Verify accuracy annually with ice-water test (32°F/0°C).

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Lunar Calendar

• Root Days: Plant during waning moon for stronger root systems.
• Leaf Days: Transplant during waxing moon for foliage growth.
• Avoid Planting: 12 hours before/after full moon or new moon.
• Microclimate Tip: Urban areas adjust timing by 1-2 weeks.
• Frost Alerts: Pair lunar phases with local frost date apps.
• Seed Soaking: Soak seeds during new moon for faster germination.

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Seed Trays

• Material Choice: Biodegradable pots reduce transplant shock.
• Drainage Holes: Prevent waterlogging with ¼-inch holes.
• Spacing: Sow 2 seeds per cell; thin after germination.
• Light Exposure: 14-16 hours under 6500K LED grow lights.
• Hardening Off: Gradually expose to outdoor conditions over 7 days.
• Labeling: Use weatherproof tags for variety tracking.

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Row Covers

• Frost Protection: Use 1.5-oz fabric for temperatures down to 28°F (-2°C).
• Pest Barrier: Secure edges with soil to deter cabbage moths.
• Ventilation: Lift covers midday above 50°F (10°C).
• UV Resistance: Replace covers every 3-4 seasons.
• Disease Prevention: Avoid contact with foliage to reduce mildew.
• Harvest Access: Install zippered panels for easy picking.

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Garden Trowel

• Blade Material: Stainless steel resists rust in wet soils.
• Depth Marks: Etched measurements for precise ¼-inch planting.
• Ergonomic Handle: Reduce hand fatigue during mass planting.
• Weeding Edge: Sharpened sides remove weeds near seedlings.
• Sanitization: Dip in 10% bleach solution between uses.
• Storage: Hang to prevent moisture damage.

Sandy soils drain too quickly for kale's robust root systems. I mix 3 inches of compost and peat moss into the soil to help retain moisture during hot afternoons. Generally, clay soils require grit - I typically add equal parts perlite and compost to the garden beds to allow for soil drainage in an otherwise water-logged environment, just as I did in my stubborn clay-raised beds in my community garden last season.

Kale's sunlight needs to change during its lifecycle. Seedlings grow best with 4-6 hours of sunlight each day. Mature plants require about 6-8 hours of sunlight daily for optimum growth. When I tested kale in Arizona, the plant made better quality leaves when it received afternoon shade to avoid bitterness. If temperatures exceed 85°F, to reduce bitter flavor, you can use shade cloth to thin the density of cells and keep leaves tender.

Drip irrigation systems are superior to soaker hoses when it comes to precision.I measured 30 percent less water waste with the targeted drip lines.Soaker hoses are useful for larger gardens but can create issues with excessive or low humidity and risk mildew in humid areas. Watering in the morning helped reduce my fungal problems by half when compared to watering in the late evening.

The pH of the soil determines what nutrients the plants will access. Kale can utilize nitrogen efficiently within a 6.0-6.5 pH. I've tested my beds every year, and I've added lime which increased the pH of my soil from a 5.4 to a 6.2 which resulted in bigger leaves. If I have soil that is acidic (below 5.5), I will add crushed eggshells to slowly improve the soil naturally, without shocking the plants.

In general, an heirloom seed such as Red Russian will take longer to germinate than hybrid varieties, for example, 7-10 days versus 5-7 days. In his experience, hybrids (Winterbor) have always produced a more uniform sprout, and heirlooms, if you can wait, have more diverse flavors. As long as the seeds are kept around 65-75F using heat mats, you can expect reliable starts in early spring.

Soil temperature is the main factor for whether roots thrive-and they won't thrive below 50°F, in which case they will stall and not grow. This is why I pre-warm my beds with black plastic for 48 hours before sowing seeds. Once sprouts lift their heads after sowing, I reduce the heat to 60°F, which makes the stems tougher because they mimic the transition from warm daytime temperatures to cool evenings in nature.

Hardening-off can help prevent frost shock after transplanting seedlings. The process will take approximately 7 days, introducing seedlings to outdoor conditions starting with an hour of morning sun on day 1. By day 5, leave plants outside overnight once evening temperatures stay around 35°F. In USDA plant hardiness zones 3-5, I often use cloches for unexpected late frosts.

You can harvest greens once the leaves are 8-12 inches and are showing a rich color, like vibrant green for Curly Scarlet or purple-veined for Rainbow Lacinato. Begin by harvesting outer leaves first, leaving the center rosette. This encourages the plant to grow again, allowing for 3-4 months of harvests.

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Seed Trays

• Cell Size: 1.5-inch (3.8 cm) cells prevent overcrowding
• Drainage: ¼-inch holes per cell avoid waterlogging
• Material: Biodegradable peat reduces transplant shock
• Labeling: Weatherproof tags track planting dates
• Sterilization: Soak in 10% bleach solution between uses
• Depth: Sow seeds ¼ inch (0.6 cm) below soil surface

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Grow Lights

• Spectrum: 6500K daylight LEDs mimic summer sun
• Height: 4-6 inches (10-15 cm) above seedlings
• Duration: 14-16 hours daily prevents legginess
• Timer Use: Automated schedules ensure consistency
• Heat Output: Low-heat design protects tender leaves
• Energy Cost: 15W per shelf reduces electricity use

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Harvest Shears

• Blade Type: Bypass design for clean cuts
• Sanitization: Wipe with 70% alcohol after each use
• Cut Angle: 45° slice promotes quick healing
• Storage: Hang in dry area to prevent rust
• Grip: Ergonomic handles reduce hand fatigue
• Sharpening: Hone monthly with whetstone

Fabric containers have superior drainage compared to plastic pots, decreasing the chance of root rot in indoor conditions. In my experience, I've grown Lacinato kale in 10-gallon fabric containers and they dried out 50% faster than similar plastic containers! If you're using plastic buckets you will need to drill ½ inch drainage holes every four inches. Skip that step and your roots will be waterlogged.

Robust kale needs about 30-40-watt LED grow lights per square foot. My shelf is 2x4 ft and I use two 250W full spectrum lights at a height of 18 inches above the shelf. I recommend bulbs rated 6500K to grow dwarf varieties like Dwarf Blue Curled, which will increase leaf production without burning the plants.

A mixture of 5:3:2 is excellent for roots in confined spaces, consisting of 5 parts potting soil, 3 parts compost, and 2 parts perlite. I have followed this mixture for 3 summers growing in self-watering containers. Dense garden soil should be avoided because it will compact and slow root growth. You can always sub rice hulls in place of perlite. Rice hulls will be more sustainable, provide aeration, and reduce spoilage.

Choose container sizes based on the mature height of the plants. A 10-gallon container is adequate for 3-foot-tall Winterbor kale. If your growing situation is compact, you may want to consider using 5-gallon buckets to grow 18-inch-tall Dwarf Siberian kale. By planting every 3 weeks, I've harvested 2 pounds of kale each month from one bucket,just a couple handfuls of leaves each time!

Organic pesticides such as neem oil and Bacillus thuringiensis (Bt) spray act slower than synthetic pesticides and allow for the protection of beneficial insects. I controlled cabbage worms in my garden by spraying with Bt sprays every 4 days during an outbreak. Synthetic pesticides such as spinosad act more quickly and may be applied every ten days. But, you will want to take care not to apply spinosad on or near plants in the flowering stage to protect pollinators.

Widespread infestations require consistency in control. For aphid outbreaks, I go with spraying an organic insecticidal soap in the morning before sunrise, every three days for two weeks. For synthetic pyrethrins, I reduce my spraying to every seven days, but be sure to wear gloves as the residues typically stay on the leaf longer than the neem-based insecticidal soap.

Companion planting is a natural way to discourage pests in your garden. I use nasturtiums to draw aphids away from my kale, marigolds to repel root-knot nematodes, and I mix in thyme and dill on the corners of my garden for the cabbage moth. The aroma of the herbs makes it harder for the larvae to find the kale! In my last garden, I experienced nearly a 70% reduction in pest damage.

Weak plants invite trouble. Kale deficient in calcium will crack open, allowing aphids access. Yellowing plants, caused by a low nitrogen supply, will succumb to flea beetles. I always incorporate crushed eggshells in my soil before planting and side-dress with blood meal around the middle of the season. Healthy, strong leaves resist pests much better than stressed plants.

Understanding how to grow kale includes being confident in the crop's ability to provide food year-round. While the summers can be short in a zone 3 garden, and it can be mild in a zone 10 winter, kale can grow in both climatic extremes. I have even overwintered a few kale plants under the snow and harvested fresh leaves in March! Kale's ability to tolerate frost makes it a four-season crop.

The success in maintaining a garden comes down to soil and pest management strategies. Compost-rich beds and neem sprays every week are two strategies I rank highly. Companion plants, like thyme--paired with nitrogen-based fertilizers--work just as well if not better than chemical alternatives to repel cabbage worms. I lost my first crop of cabbage to aphids, and now, I interplant nasturtiums close as sacrificial plants that attract aphids and save my harvests from chemical interventions.

Use Red Russian for salads and Lacinato for soups, with unique textures from both varieties. I mix 3 types in my garden, staggered every 3 weeks. This guarantees harvests and shows which strains grow better based on your local microclimate, turning trial into success.

Containers provide you with 60% of your kale grown in the ground but work well on patios. I grow Dwarf Blue Curled in 7-gallon buckets, watering every day. Growing in the ground involves fewer maintenance chores, though it does require more space. You can choose whichever option is most important to you, convenience or quantity, and let the very nature of kale carry the balance.