Kale is a beloved crop in my garden, where we reserve two plots exclusively for its cultivation. This dedication allows us to enjoy a steady supply of fresh greens for an extended period. Despite its hardiness and versatility, growing kale can still be challenging. When our kale struggles, well-meaning friends often express concern but lack practical advice.
Troubleshooting issues with this crop can be particularly daunting, as some of the easiest plants to grow may be the most difficult to diagnose. If you’re experiencing a disappointing harvest, you’re not alone – numerous factors can contribute to underperformance. In fact, I’ve identified 15 common problems that can impact kale growth and offer practical solutions for overcoming them.
The Most Common Kale Growing Problems
Red Russian kale has earned a special place in our household – its tender leaves are perfect for eating raw, and its hardiness allows it to thrive until the first frosts of autumn. Even as other leafy greens like lettuce and Swiss chard succumb to the changing seasons, our kale often remains green and growing until snowfall arrives. Yet, despite its resilience, kale is not immune to challenges.
Pests are a common problem, with larger ones like groundhogs and rabbits exhibiting a peculiar preference for brassicas over other garden staples. In my experience, I’ve encountered a particularly enthusiastic groundhog that targeted every single brassica in my garden without bothering any other plant. While kale is generally less susceptible to disease than some other plants, it’s still important to keep an eye out for potential issues.
Fungal or bacterial infections can quickly spread through kale beds if the conditions are right. To promote healthy growth and prevent such problems, I recommend maintaining a clean, well-drained, and sunny garden bed. Regularly remove weeds, debris, and other obstructions to ensure optimal growing conditions. While this may not entirely eliminate the risk of infection, it will certainly reduce the likelihood.
Furthermore, it’s essential to remain vigilant for common kale diseases, even in the best-tended gardens, as they can still occur from time to time.
Leaves Have Holes
When it comes to common kale pests, one culprit often goes unnoticed – the cabbage white butterfly (Pieris rapae). These small, delicate butterflies may seem harmless, but they can unleash a swarm of green caterpillars into your garden. The resulting damage can be devastating, with leaves ravaged and droppings scattered across your plants.
Preventing an infestation is key.
Row covers are an effective solution, as they prevent the butterflies from laying eggs on your kale plants in the first place. Alternatively, you can remove eggs that have already been laid by gently spraying the underside of leaves with insecticidal soap.
If an infestation has already occurred, it may be necessary to manually remove the caterpillars from your plants. These tiny worms tend to blend into their surroundings, but a closer inspection will reveal them.
Once you’ve collected a small quantity, consider feeding them to your chickens or disposing of them in soapy water.
While releasing your chickens into the garden to hunt cabbage worms can be an effective solution, keep in mind that they may also consume your kale leaves alongside the pests. For more comprehensive guidance on controlling cabbage whites, refer to our dedicated guide.
Stunted Growth and Ragged Holes
When you notice your plants appearing stunted with ragged holes scattered throughout their leaves, it’s likely the work of cabbage loopers (Trichoplusia ni). These caterpillars resemble beefed-up relatives of cabbage white butterfly worms, causing similar damage. As they grow into gray moths, they leave behind a trail of destruction. To prevent these pests from taking hold, consider using row covers or manually removing them and feeding them to your birds.
Both cabbage loopers and their cousins, the cabbage worms, respond well to Bacillus thuringiensis (Bt), a bacteria-based pesticide that specifically targets leaf-feeding insects. Notably, Bt is deemed safe for bees, other pollinators, humans, and animals, making it a reliable solution for organic gardeners.
Weak Plants and Yellow Leaves
Aphids are perhaps the most ubiquitous pests in any list of garden invaders, regardless of whether you’re cultivating kale indoors or outdoors. Among these unwelcome visitors, cabbage aphids (Brevicoryne brassicae) pose a significant threat to kale’s health and vigor. Characterized by their woolly, gray-green appearance, these pesky creatures feast on the sap of kale and other brassicas, causing telltale signs of yellow stippling or overall discoloration, as well as stunted growth.
Fortunately, once you’re armed with the right strategies, aphids are relatively straightforward to manage. A concoction of insecticidal soap or a treatment of neem oil can prove effective in keeping these pests at bay.
Crisp, Brown Leaves and Thin Spots
When warm weather sets in, harlequin bugs emerge in full force, posing a threat to kale plants grown throughout the summer. For some gardeners, clearing the garden of brassicas for a few weeks in late June can be an effective way to combat these persistent pests. However, this solution may not be feasible for those with shorter growing seasons. Instead, I take a more hands-on approach by removing these slow-moving insects from my kale plants and incorporating them into my chickens’ diet.
Another option is using a glass jar filled with kerosene to humanely capture the harlequin bugs. Regardless of the method chosen, it’s essential to remember that kale is a resilient crop. If necessary, it can be pruned back or even reseeded later without compromising its overall health.
Tiny Shotholes in Foliage
When you spot tiny holes in the leaves of your kale, it’s probably a sign that flea beetles have taken up residence. These pesky insects often flourish in gardens where fall cleanup is neglected and regular weeding doesn’t become a habit. To tackle the problem, try treating the affected areas with a homemade pesticide blend consisting of 3 parts water, 1 part rubbing alcohol, and 1 part dish soap. Alternatively, dusting the leaves with talcum powder can also help deter these unwanted visitors.
Just be sure to thoroughly rinse your kale leaves before consumption after applying either method.
Rotting Leaves
Black rot is a bacterial infection caused by Xanthomonas campestris pv. campestris that can quickly devastate kale crops. Initially, small brown spots appear on leaves, but the disease rapidly progresses, leaving your kale plants with black, decaying leaves that fall to the ground. This is certainly not a desirable outcome for any kale grower. Factors such as dampness, humidity, poor airflow, and insufficient sunlight can contribute to the development of black rot in kale plants.
Even in ideal growing conditions, excessive rainfall or prolonged humid seasons can also trigger an outbreak. If black rot does occur, it’s essential to remove affected plants and leave the bed fallow for a season to effectively kill off the bacteria.
Brown and Gray Spots on Leaves
Fungal diseases like Alternaria leaf spot can devastate a kale crop, causing brown and gray spots to form on leaves. This common problem occurs when fungi such as Alternaria brassicicola and A. brassicae thrive in damp, humid conditions. If you notice signs of infection, treat your kale with a fungicide as soon as possible. While commercial fungicides can be effective, I prefer to avoid them whenever possible and instead opt for natural remedies like copper sprays.
These sprays can slow the spread of fungal diseases, including downy mildew, but they won’t cure existing infections. When using a copper spray, remove infected plants first, then apply the treatment to the remaining kale. If your garden has a history of fungal issues, consider applying a copper spray preemptively to prevent infection. In gardening, it’s often said that ‘the best defense is a good offense.
‘ To keep your garden healthy and reduce the risk of fungal infections, maintain a tidy environment by removing debris, weeds, and last year’s leaves. Plant in well-drained soil and provide ample space between plants. If you want to give your kale an extra layer of protection against fungal diseases, use a copper spray to create a hostile environment for these pathogens.
While copper sprays won’t combat bacterial infections, companion planting with naturally anti-bacterial herbs like garlic, onions, oregano, and thyme can help reduce the risk of bacterial diseases.
Irregular, Dry Brown Spots on Leaves
When it comes to kale, one of the most troublesome fungal diseases is Anthracnose (Colletotrichum higginsianum). This pesky fungus thrives in rainy conditions, causing dry, circular lesions on the leaves of your prized kale plant. The worst part? Once it sets its sights on your greens, getting rid of it becomes a Herculean task. To combat this unwanted invader, consider pulling up and destroying any infected plants. Additionally, be sure to provide ample space between your kale plants.
By doing so, you’ll hinder the fungus’s ability to spread from plant to plant, as sunlight and airflow can help keep its growth in check.
Fuzzy Coating on Leaves
Downy mildew, caused by the fungus-like pathogen Peronospora parasitica, manifests itself as a fuzzy or downy coating on the underside of leaves, accompanied by white or yellow patches. It’s an unwelcome sight in any garden! The disease thrives in damp, humid environments, which is why recent wet and cool weather provided an ideal breeding ground for its proliferation.
In such conditions, the most effective countermeasures are extra row spacing and consistent weeding to prevent it from spreading further.
Powdery mildew, another fungal pathogen, can also produce fuzzy growth, but typically begins with white patches that eventually turn into a fuzzy coating. If you’re struggling with this issue, be sure to check out our comprehensive guide for identifying and treating powdery mildew, which offers valuable insights and solutions.
Wilting Leaves
Kale is notoriously finicky about temperature, thriving in conditions where temperatures stay within the 70s Fahrenheit range. It also requires consistent moisture levels, as drought or excessive heat can cause leaves to droop and wilt. If you suspect water stress, simply provide a good soaking. For hot spells, consider providing shade by draping shade cloth over the plants during peak sun hours. Misting with a hose can also help alleviate discomfort.
However, if neither of these solutions address the issue, it’s likely that pests or diseases are at play. In this case, inspect your kale for signs of infestation or infection, as outlined above.
Leaves Turning Purple
Before jumping to conclusions, take a closer look at your kale’s seed packet or info card. It’s possible you’ve planted a purple-leafed variety without realizing it. If you’re certain that your kale should have green leaves, then a nutrient deficiency might be the culprit. Phosphorus insufficiency can cause discoloration, so test your soil and consider adding phosphorus if necessary.
Alternatively, young leaves may have been exposed to unusually cool temperatures, which can also cause discoloration. In this case, monitor the plant’s progress – it’s possible the leaves will continue to grow normally with time.
Leaves Turning Pale Green
When observing pale green leaves on your kale, it’s often a sign of insufficient nitrogen levels in the soil. To address this issue, conduct a thorough soil test to determine the nitrogen content. If the results indicate a deficiency, supplement with nitrogen-rich fertilizers like blood meal, which provides a concentrated dose of nitrogen without introducing excessive elements.
For an eco-friendly and effective solution, consider Down to Earth’s products, which not only promote healthy plant growth but also prioritize environmental sustainability.
Stunted or Leggy Growth
Kale growth issues often manifest as leggy or stunted foliage. When one of the essential factors for healthy development is out of balance, plants may exhibit undesirable growth patterns. This can stem from imbalances in water, nutrients, or sunlight intake. Specifically, limited sunlight exposure can lead to elongated, spindly stems, while inadequate nutrition and moisture are more likely to result in stunted plant growth.
Soil conditions also play a crucial role; an excessively acidic or alkaline environment can impede growth, as kale thrives in a slightly acidic to neutral pH range of 5.5-6.8. Finally, overcrowding – whether due to proximity to other plants or weed competition – can similarly hinder growth and produce stunted plants.
Weak or Dying Seedlings
Kale, like many brassicas, is prone to damping off disease. This fungal affliction is caused by various oomycete pathogens, including those in the Pythium, Fusarium, and Rhizoctonia solani genera. Sometimes, seeds may not germinate at all, but if they do, the resulting seedlings will often be weak and exhibit a soggy base near the soil line. For more information on recognizing, preventing, and treating this issue, refer to our comprehensive guide.
Plants Cut Off at the Base
The humble kale plant can fall victim to a variety of unwanted diners. One common culprit is the cutworm, which has a peculiar habit of chewing off the plant at its base. Upon emerging outside, you may be greeted by the unappealing sight of leaves strewn about in a heap. A simple yet effective solution lies in the use of collars to safeguard your kale. Meanwhile, omnivores such as rabbits, deer, and even birds are known to consume entire kale leaves given the opportunity.
To mitigate these issues, consider employing cloches, fences, or row covers to protect your kale from these unwanted munchers.
