Brassica oleracea (Brassicaceae or cabbage family)
Production, Main Crop
Soil preparation
- Kale should not follow other cole crops.
- Apply compost and other amendments based on the results of a soil test.
- Spread lime as needed to increase both the pH and Ca levels. Dolomite lime will also increase Mg levels. Spread gypsum when calcium levels are low but pH is correct.
- A fertilizer company can add OMRI-listed potassium sulfate to compost if it doesn’t have enough K to meet the crop’s needs. If this isn’t possible, spread the correct amount of fertilizer and incorporate it before planting. Alternatively, you can side-dress it during cultivation. Divide the recommended rate of the soil test in half if side-dressing.
- Test for boron and apply only as recommended by the soil test. A fertilizer company can add boron to compost to optimize boron distribution. If this isn’t an option, distribute soluble boron through a water solution with a sprayer directly on the soil. If applied directly on the crop don't exceed more than 1 lb. of boron per acre to avoid leaf burn.
- Summer-planted kale does well when following a spring seeding of field peas, bell beans, barley and oats. In this case it doesn’t need additional application of N.
- Incorporate compost and amendments, and plant kale as a field crop or in raised beds.
Common recommended fertilizer rates1
| Nitrogen | Phosphorus | Potassium | pH |
| 120 | 20-160 | 0-200 | 6.2-6.5 |
| 1Rates are for New York and are from Cornell University’s Nutrient Guidelines for Commercial Vegetable Production (2019). Check the Cornell website for updated guidelines, or consult with local experts for recommended rates outside New York. | |||
Varieties
- Washington State variety trial
- Darkibor, Winterbor, Redbor, Lacinato, Black Magic, Red Ursa
Greenhouse guidelines
- EZ Seeder seeding plate #16
| Cell pack tray | Germination temp | Growth temp | Hardening off | Notes |
| 72, 98 or 128 | 65°–85° | Cool | Withhold water | Put plug trays on a wire mesh bench to encourage air pruning. Take plants outside 1 week before planting in the field. |
Transplant readiness indicators
- Plants should easily come out of their cells. Plants should generally not be older than 5 weeks.
- Harden plants off outside; plants that are lush don’t perform well in the field.
Transplanting in 5- or 6- foot raised beds
| Rows | In-row spacing | Planting depth (inches) | Notes |
| 2 | 12-18 inches | As deep as the plant can tolerate | Kale is a tough plant but can be decimated by flea beetles when not looked after. |
Cultivation procedures
- Adjust mechanical transplanters so there is good contact between the plug or root ball and the soil. Ensure plants are properly rooted before cultivation.
- Use sweeps (with torsions if possible) followed by a finger weeder 7–10 days after transplanting, or as soon as possible without damaging the plants. Alternatively, use a tine weeder; but this works better when you use bare root transplants because tine weeders tend to uproot plugs.
- Hand hoe between plants as necessary.
- Use a finger weeder in combination with side knives for a second pass. Alternatively, if you want very slight hilling, use spring hoes in combination with side knives.
- If you need to cultivate a third time, use Lilliston rolling cultivators and hill carefully without burying the plants.
Disease and insect protection
- Control black rot (Xanthomonas) by purchasing clean seeds, keeping the greenhouse clean and exposing seed to hot water treatment. Some organic seed suppliers hot treat their seeds, so check with them before applying your own treatment, as double treatment can affect germination.
- Flea beetles
- Cover the crop with floating row covers or insect netting before emergence to avoid flea beetle damage. Keep covered until harvest. Alternatively, use a spinosyn-based product like Entrust.
- If possible, follow Extension bulletins that publish the timing of each generation of flea beetles, or place yellow sticky cards at plant height to monitor their presence. Check the cards at least twice a week.
- Spray beneficial nematodes on heavily infected land to control flea beetle grubs and avoid future generations. Flea beetles tend to overwinter in nearby hedgerows and grass strips.
- You can prevent cutworms by spraying the soil with the beneficial nematode Steinernema carpocapsae. Once the pest is in the crop, control the population by spraying the crop with Bacillus thuringiensis kurstaki, or spread a baited product containing spinosyn, like Seduce, around the plants.
- Cabbage maggots: To reduce infestation of cabbage maggots on young seedlings, cover seedlings with floating row covers or insect netting as you would for flea beetles. Maggots appear in 3–4 generations in the Northeast, starting in early spring.
- To avoid Alternaria leaf spot, plant either far away or upwind from earlier planted cole crops and avoid overhead irrigation. Regular applications of Bacillus amyloliquefaciens, available as Double Nickel, have shown the best controls in research. Bacillus subtilis, available as Serenade, and mineral oil like JMS Stylet-Oil has shown some control for a few growers. Regular sprays with giant knotweed extract, such as Regalia, appear to reduce Alternaria as well by activating the plant’s natural defenses against fungal and bacterial diseases.
- Scout for the eggs of imported cabbage worms or diamondback moths on the underside of leaves. When the small worm population is over 2 per plant, spray a Bacillus thuringiensis (Bt aizawai or Bt kurstaki) product, such as XenTari, or a spinosyn-based product, such as Entrust, every week until the population is under control. Alternate your spraying schedule by using Bt products along with a spinosyn-based product to avoid resistance buildup.
Other cultural practices
- Irrigate frequently for optimum yield and plant health. Frequency depends on soil type, evaporation, precipitation and the particular needs of the crop.
Cover cropping and/or double cropping
- Kale harvest can continue late in the season and generally doesn’t get worked under before the winter. For best results with a cover crop, broadcast rye seed in August or September and mow the stalks down after the last harvest
Brassica napus pabularia (Brassicaceae or cabbage family)
Production, Kale Mix and Mustard Greens
Use the following guidelines for any kale mix on the market, either by itself as Russian kale or in a mix with crops like mizuna.
Varieties
- Red Russian kale, Lacinato kale, red mustard, green mustard, mizuna, etc.
Direct seeding information
| Seeder | Rows | Seeds per foot | Seed plate no. | Depth (inches) | Sprocket setting | Notes |
| Planet Jr. | 5 | 50 | 2 or 3 | Depth 2 | Use spreader shoe | |
| Sutton Jr. | 10-20 | 30 | 6 | 1/4 | 1 mph | |
| Jang | 5 | 12 | YYJ 12 or YYJ 24 | 1/4 | Front 14/rear 10 |
Other cultural practices
- Follow many of the cultural practices outlined in the Kale, Main Crop section.
- Some mixes allow for a second cutting.
Cover cropping and/or double cropping
- You can plant a short-season vegetable crop like salad mix or spinach after early-planted harvested kale greens.
- For later dates, work under any harvest remains to avoid insect or pathogen buildup, and plant a cover crop. In the northern United States and Canada, you can follow summer- and early-fall-harvested mustard or kale greens with a cover crop of oats and peas in September, or rye and vetch planted at later dates. Adjust accordingly in other regions.
Harvest
| Yield | An average of 1 bunch per row foot with increased yield after successive harvests. |
| Standards | Harvesting1 60-100 bunches per person per hour. |
| Washing 175 bunches per person, per hour | |
| Tools and supplies needed | Knives, rubber bands or twist ties (customer preference may influence this), and 1 ¾-bushel plastic boxes |
| 1Harvest rates don't include the time required to transport crops from the field to a wash and pack shed or storage facility. | |
Ready-to-harvest and quality indicators
- Plants are 15–18 inches tall.
- The bottom leaves are dark green and large enough to make a bunch out of 5–6 large leaves.
Harvest procedures
- Wash hands and sanitize knives before harvesting.
- Harvest in the morning to avoid field heat accumulation.
- Use different boxes in the field than the ones you use for distribution.
- Grab a bunch of the biggest leaves near the stem of the plant and snap them off.
- Leave the smaller leaves at the top of the plant and any dead or yellow leaves at the bottom.
- Each bunch uses 5–6 leaves of curly kale or about 10 leaves of lacinato kale.
- Place a twist tie around the stems and then twist the bunch to tighten the twist tie, or use rubber bands.
Washing and storage procedures
- Wash hands and rinse boots before entering the wash-and-pack shed, and cover up field clothes with a bib. If a long-sleeve shirt contains soil, remove this as well.
- Kale is not always washed, but you can dunk it in ice water to remove field heat.
- Add a sanitizer to the wash water. Use the guide How to Wash Produce Using a Peracetic Acid Solution to establish how much hydrogen peroxide and peracetic acid solution to add to the water.
- Leave bunches in the water until the cores of the stems are properly cooled down.
- Pack in sealed boxes to avoid having the product lose moisture during longer storage.
Additional resources
This material is based upon work that is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture through the Sustainable Agriculture Research and Education (SARE) program. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and should not be construed to represent any official USDA or U.S. Government determination or policy.