What to Do When Kale Looks Rough: Yellowing, Holes, or Curling Leaves

I walked out one morning to a patch of kale that looked like it had been through a storm: yellowing leaves drooped toward the soil, something had clearly been munching holes in the edges, and a few plants were curling in on themselves like they’d just given up.

If you’ve grown kale for more than a few weeks, you’ve probably seen it too. The good news? Most of it’s fixable. You don’t need to rip it out and start over. You just need to know what’s causing the problem. That’s what we’re going to break down here, one leaf issue at a time.

Yellowing Kale Leaves? Here’s What Your Soil Is Telling You

If you’ve got yellow kale leaves, your crop is waving a big red flag, and most of the time, the problem starts below the soil line. Kale (Brassica oleracea, acephala group) is a nutrient-hungry vegetable, and when it can’t get what it needs, the leaves show it fast.

Common Causes of Yellowing Leaves

• Nitrogen deficiency – Kale is a heavy feeder, especially on nitrogen. When levels drop, the lower leaves turn yellow first and the problem creeps upward.

• Magnesium deficiency – Yellowing between the veins while the veins themselves stay green.

• Overwatering – Saturated soil deprives roots of oxygen, making nutrient uptake impossible.

• Poor drainage or compacted soil – Roots suffocate, leading to slow growth, leaf discoloration, and sometimes root rot.

If you’re sorting out yellow kale leaves causes—nutrient deficiency vs. overwatering—this Penn State diagnostic guide explains which symptoms map to which problems.

How to Fix It

1. Feed the crop – Side-dress plants with finished compost, fish emulsion, or another organic fertilizer rich in nitrogen.

   When kale starts yellowing from nitrogen loss, I reach for an organic fish and seaweed blend. It gives plants a quick boost and supports long-term soil health.

2. Test your soil – A simple soil test can confirm deficiencies and guide your next steps.

3. Improve drainage – If water pools after rain, loosen the soil, raise the bed, or plant on mounded rows.

4. Adjust watering – Keep soil moist but not soggy. Overwatering is one of the fastest ways to cause yellow leaves.

Pro Tip for Prevention: Practice crop rotation with other vegetables like tomatoes or beans to reduce disease pressure and balance soil nutrients.

Holes in Kale Leaves? Identify the Pests Before They Wreck Your Crop

When you spot holes in kale leaves, you’re looking at clear signs of feeding damage from common brassica pests. Knowing exactly which insect is eating your crop is the first step to effective pest control.

Want the full breakdown of every major kale pest and the exact organic control methods that work? Check out our guide: The Top 5 Kale Pests — How to Protect Kale from Bugs Organically.

Top Offenders and How to Spot Them

For a deeper look at identifying and managing flea beetles, cabbageworms, and other brassica pests, UC IPM’s cole crops guide is a gold standard reference.

How to Get Rid of the Pests Naturally

1. Flea beetles – Protect seedlings with floating row covers, dust leaves with diatomaceous earth, or sprinkle wood ash around plants.

   For a safe, chemical-free barrier against chewing insects, I keep a bag of food-grade diatomaceous earth on hand. It’s a staple in my pest control kit.

2. Cabbage worms – Hand-pick daily and destroy. Spray weekly with Bacillus thuringiensis (BT), a safe organic pesticide for caterpillars.

3. Aphids – Blast with a hose or spray with diluted insecticidal soap. Attract beneficial insects like ladybugs and lacewings by planting dill, yarrow, or alyssum nearby.

UMN Extension outlines practical scouting and controls for flea beetles (and caterpillar pests on cole crops), including when to prioritize row covers, diatomaceous earth, and BT.

Prevention Tips for Long-Term Pest Management

• Row covers from day one – Keeps moths, beetles, and other insects from reaching seedlings.

• A quality floating row cover is one of the easiest ways to keep pests off your kale from day one. I use these to protect young seedlings from flea beetles and cabbage worms without a drop of spray.

  

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• Crop rotation – Avoid planting kale or other brassicas (like broccoli, cabbage, or cauliflower) in the same spot two years in a row to disrupt pest life cycles.

• Companion planting – Nasturtiums act as a trap crop for aphids. Garlic and onions help repel cabbage moths and other pests.

• Healthy soil – Well-fed plants resist insect pressure better than stressed ones.

Pro Tip: Monitor plants daily. Early detection is the easiest pest control you’ll ever do.

Curling Kale Leaves? Pinpoint the Stress Before It Spreads

When kale leaves start curling, it’s tempting to blame pests. But most of the time, it’s an environmental stress problem, not an infestation. Kale is hardy, but sudden changes in conditions can cause leaf distortion that affects the entire crop.

Common Causes of Leaf Curl

• Heat stress – In hot summer weather (especially Zones 7+), kale can wilt and curl to conserve moisture.

• Cold shock – Planting seedlings too early or getting hit by a late frost can cause leaf curl and slowed growth.

• Wind exposure – Constant wind dehydrates leaves faster than roots can replace moisture.

• Crowded spacing – Too many plants competing for nutrients, light, and airflow creates stress and increases disease risk.

How to Correct Curling Leaves

1. Thin plants – Maintain 12–18 inches between plants to reduce competition and improve airflow.

2. Mulch generously – A 2–3 inch layer helps regulate soil moisture and temperature.

3. Prune damaged leaves – Removing severely curled leaves redirects energy to healthy growth.

4. Provide shade – Use a lightweight shade cloth during peak summer heat to prevent wilting and curling.

Prevention Tips

• Harden off seedlings before transplanting to avoid cold shock.

• Plant in partial shade during the hottest months.

• Maintain even soil moisture — stress from drought followed by overwatering often triggers leaf curl.

• Rotate crops to keep soil health balanced and reduce disease pressure from previous brassica plantings.

Grandma’s Tip: “Plants don’t like drama — give ‘em steady care, and they’ll give back steady harvests.”

When to Prune, Compost, or Replant Kale

Not every kale plant problem can be fixed. Sometimes the best decision for your crop, and your sanity, is knowing when to cut your losses.

The trick is recognizing whether your plant can bounce back or if it’s time to compost and start fresh.

When to Prune

Pruning works when the plant is still healthy overall and the issue is isolated to a few leaves.

• Minor pest damage that hasn’t reached the crown

• Yellow leaves at the bottom caused by age or early nutrient deficiency

• Slight curling or wilting from temporary stress

How to prune: Use clean garden shears, cut damaged leaves at the base, and avoid removing more than one-third of the plant at once.

And when your kale’s thriving again, make sure you harvest it in a way that keeps it producing for weeks. Here’s our full step-by-step: How to Harvest Kale the Right Way (So It Keeps on Giving).

When to Compost

Composting is the best choice when leaves are too far gone to save and may risk spreading disease.

• Severe infestations of pests like cabbage worms or aphids

• Fungal leaf spots (Alternaria leaf spot, downy mildew, black rot)

• Wilting or rotting leaves from poor drainage or root rot

Pro tip: Don’t compost heavily infested or diseased material unless you hot-compost above 140°F to kill pathogens and larvae.

When to Replant

Sometimes a plant just won’t recover — especially late in the season.

• Stems are thin, spindly, or collapsing

• Roots are mushy or foul-smelling from root rot

• Pest damage has stripped the plant to bare stems

• Crop is so stunted it won’t mature before the season ends

Seasonal tip: In Zones 5–7, a late-summer replant often produces sweeter leaves after a touch of frost.

Kale Rescue Checklist: Diagnose and Fix Problems Fast

When your kale crop starts showing signs of stress — from yellow leaves to pest damage — speed matters. Use this quick-reference guide to match the symptom to the cause and apply the right fix.

Kale Problem Diagnosis Table

Download this image or keep it on your phone. Spotting and fixing kale plant problems early can mean the difference between a thriving crop and a bed that needs replanting.

Grandma’s Tip: “Know the signs, act fast, and you’ll eat more greens than the bugs do.”

What Not to Do When Dealing with Kale Plant Problems

Sometimes the fastest way to ruin a good kale crop is by “fixing” it the wrong way. Avoid these common mistakes to keep your plants healthy and producing.

Top Kale Growing Mistakes to Avoid

• Overfeeding late in the season – Too much nitrogen promotes tender, pest-attracting growth and delays maturity.

• Crowding plants – Tight spacing reduces airflow, increases humidity, and encourages fungal diseases like Alternaria leaf spot and powdery mildew.

• Ignoring pests – Insects like flea beetles, cabbage worms, and aphids multiply fast. Delay action, and you’ll face a full infestation.

• Planting in the same spot each year – Skipping crop rotation invites soil-borne diseases such as black rot and downy mildew to build up.

Pro Tip: Healthy kale starts with prevention. Keep your beds weed-free, feed the soil instead of just the plant, and check leaves regularly for early signs of damage or disease.

Kale Problems by Season (Zones 4–7)

Knowing when certain kale plant problems are most likely to appear helps you stay ahead of pests, diseases, and environmental stress. Different seasons bring different challenges for this brassica crop, and prevention starts with timing.

Seasonal Kale Troubleshooting Guide

Zone-Specific Tip:
In Zones 5 and 6, a late-summer planting of kale often produces the sweetest leaves after a light frost — cooler nights improve flavor and reduce pest pressure.

Ugly Kale Can Still Feed You

Not every kale plant problem means the end of your harvest. Kale is one of the toughest crops in the garden — it can take pest damage, bounce back from weather swings, and still put fresh greens on your table.

It won’t always look perfect. Leaves may turn yellow from nutrient deficiencies, curl from heat stress, or show holes from pests like flea beetles or cabbage worms. But with quick action and a little know-how, most issues can be corrected before they take over the crop.

So if your kale looks rough, don’t pull it up in frustration. Diagnose the problem, make the fix, and use what you’ve learned for the next planting. A healthy bed of kale is worth the work — for both your plate and your pride.

Kale Problems FAQ

1. Why are my kale leaves turning yellow?

Yellow kale leaves are usually caused by nitrogen deficiency, overwatering, or poor drainage. Check your soil moisture first — soggy roots can’t take in nutrients. If drainage is fine, side-dress with compost or apply a diluted fish emulsion to give the crop the nutrient boost it needs.

2. What is eating holes in my kale leaves?

The most common culprits are flea beetles, cabbage worms, and aphids. Flea beetles leave tiny “shotgun” holes, cabbage worms chew larger ragged holes, and aphids cause curling and sticky residue. Identify the pest first, then choose the right control method — such as Bacillus thuringiensis for worms or diatomaceous earth for flea beetles.

3. How do I get rid of pests on kale naturally?

Use floating row covers to block insects, hand-pick caterpillars daily, and apply insecticidal soap or neem oil for soft-bodied pests like aphids. Companion planting with garlic, onions, or nasturtiums can help deter common kale pests while attracting beneficial insects.

4. Why are my kale leaves curling but not eaten?

Curling without visible chewing is usually a sign of heat stress, cold shock, wind damage, or overcrowding. Mulch to maintain soil moisture, thin plants for airflow, and use shade cloth in high heat.

5. Can I eat kale that has holes from pests?

Yes — as long as the plant is otherwise healthy and free from disease, kale with pest holes is safe to eat. Just wash the leaves thoroughly to remove any eggs, frass (insect droppings), or residue.

6. How can I prevent kale diseases like black rot or downy mildew?

Rotate crops each season, avoid overhead watering, and space plants properly to improve airflow. Remove any diseased leaves immediately and avoid working in the garden when foliage is wet, as moisture spreads pathogens quickly.

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