What NOT to Plant with Cucumbers: 7 Worst Garden Neighbors

Last updated on May 20, 2025

Imagine a season of abundant, crisp cucumbers… but what if invisible enemies in your garden are holding them back? Have your cucumbers ever looked sickly despite your best efforts? You water them. You feed them. They get plenty of sun. Still, the leaves look yellow. The vines seem weak. You’re just not getting many fruits. It’s enough to make you scratch your head!

The problem might be closer than you think. It could be right in your garden bed! As planting season is here or approaching in many areas, now is the perfect time to think about who your cucumbers will share space with.

Based on extensive horticultural research and expert gardening advice, understanding what should you not plant around cucumbers is a total game-changer. Trust me. Avoiding these bad companion plants for cucumbers is simple. It’s also one of the most effective ways to boost your harvest. It keeps your cucumber patch happy and healthy.

It’s all about smart cucumber companion planting. Sometimes that means knowing who not to invite to the party!

Why Does Who Your Cucumber Hangs With Even Matter?

Think of your garden like a neighborhood. Some folks get along great. They share tools. They help each other out. That’s good companion planting! But then there are those neighbors who cause problems. They hog the sidewalk. They play loud music all night. They just generally make life difficult. That’s what happens when you plant antagonistic plants for cucumbers.

The Problem: Competition and Shared Enemies

They compete for vital resources. These include nutrients, water, and even sunlight. And worse? They can attract the same pests. They can share diseases. This turns your garden into a hot mess express.

The Impact: Seeing Bad Relationships in Your Garden

You’ll actually see the impact of these bad relationships. Maybe the leaves start looking pale or yellow. They should be vibrant green. Or the vines just don’t seem to grow vigorously. You might even notice fewer flowers. This means way fewer cucumbers!

In the worst cases, your plants could be severely stunted. They might constantly battle pests. They could succumb to diseases. This leaves you with a harvest that’s only half of what it could be. Or even less! Knowing which plants are harmful to cucumbers is just as crucial as knowing the good guys!

Ready to dive into the dirt on which plants are the worst offenders? Let’s dig in! We’ve identified 7 plants that your cucumbers definitely won’t thank you for planting nearby.

7 Worst Companion Plants to Avoid with Cucumbers

Here are the 7 plants that can cause the most trouble for your cucumber patch:

1. Squash, Melons, and Pumpkins
2. Aromatic Herbs like Sage and Rosemary
3. Potatoes
4. Fennel
5. Mint
6. Brassicas (Broccoli, Cauliflower, Cabbage)
7. Black Walnut Trees

Now, let’s look at why each of these is a problematic neighbor for your cucumbers.

1. Why are Squash, Melons, and Pumpkins Bad Companion Plants for Cucumbers?

Answer: Squash, melons, and pumpkins are bad companion plants for cucumbers primarily because they compete intensely for nutrients, water, and space, and they share many common pests and diseases like cucumber beetles and powdery mildew.

Okay, this might sound weird, right? Cucumbers belong to the cucurbit family. So do squash, melons, and pumpkins. You’d think they’d be best buds! But honestly, planting them too close is often a recipe for trouble.

Resource Competition

Why? Well, for starters, they’re all super hungry. They’re also thirsty. Planting them together means they literally fight for every drop of water. They fight for every bit of food in the soil. Your poor cucumber vines might lose out. This leads to plants that stunt cucumber growth.

Shared Pests and Diseases

And here’s the real kicker: they share a whole roster of common enemies. We’re talking about the dreaded cucumber beetles. We’re talking about squash bugs. And diseases like powdery mildew and bacterial wilt.

If one plant gets sick or infested, it’s like a potluck for pests and diseases. It spreads rapidly through the entire cucurbit family. It’s just too risky! I learned this the hard way one year. A squash bug infestation on my pumpkins quickly migrated to my cucumbers. It decimated the crop. It was a total bummer!

So, while they’re family, it’s often best to give squash, melons, and pumpkins their own space in the garden. This minimizes shared pest and disease issues.

How to avoid shared pests and diseases with cucurbits: Give squash, melons, and pumpkins their own separate space away from your cucumbers. It’s a tough love kind of situation for smart cucumber garden planning.

The Three Sisters Exception

Now, you might have heard of the “Three Sisters” method. This is a traditional Native American planting technique. It does include squash alongside corn and beans. This system works beautifully. The plants support each other. The corn provides a trellis for the beans. The beans fix nitrogen in the soil. This feeds the corn and squash. The sprawling squash leaves act as a living mulch. This suppresses weeds. It keeps the soil moist. It’s a truly symbiotic relationship!

But here’s the key difference: the Three Sisters is a carefully balanced system. Simply planting squash and cucumbers next to each other without the other elements doesn’t provide those mutual benefits. Instead, it just highlights the competition and shared pest/disease problems. So, while squash is a great “sister” to corn and beans, it’s generally a problematic neighbor for cucumbers. This is true when they’re just planted side-by-side in a typical garden bed.

2. Why are Aromatic Herbs like Sage and Rosemary Bad for Cucumbers?

Answer: Highly aromatic herbs like sage and rosemary are bad for cucumbers because they can stunt their growth, potentially confuse beneficial insects needed for pollination, and their differing moisture needs make them unsuitable neighbors.

I know, it’s a shocker!

Confusing Beneficial Insects

Think about strong-smelling herbs like sage, rosemary, and even some types of basil. While fantastic in the kitchen, their intense aromas can sometimes negatively impact your cucumber vines. Their growth habits can too. For one thing, their strong scents might actually confuse beneficial insects. Cucumbers need these for pollination. Plus, some gardeners report that planting these herbs too close can lead to stunted growth in plants. It’s like the herbs are just too bossy!

Different Moisture Needs

Another big issue is their varying moisture needs. Cucumbers are total water hogs. They need consistently moist soil. This produces those juicy fruits. Herbs like sage and rosemary, however, prefer drier conditions. This is true once established.

Trying to keep both happy in the same soil patch is like trying to please everyone at a family dinner. It’s nearly impossible! You’ll either underwater the cucumbers. Or you’ll overwater the herbs. Neither is good for garden health.

So, while I love these herbs, I definitely keep them in a different part of the garden. It’s far away from my cucumber patch.

How to avoid stunting cucumber growth with aromatic herbs: Plant strong-smelling herbs like sage and rosemary in a separate area of the garden. It’s just one more thing to consider for effective cucumber companion planting. It helps in knowing which plants to keep away from cucumbers.

3. Why are Potatoes Bad for Cucumbers?

Answer: Potatoes are bad for cucumbers because they are highly susceptible to blight diseases that can easily spread to cucumbers, and they create intense competition for nutrients and water in the soil.

Alright, let’s talk potatoes. Everyone loves homegrown potatoes. But they are definitely on the list of what should you not plant around cucumbers. You might be asking, “Why shouldn’t I plant potatoes with cucumbers?“

Blight Susceptibility

Well, potatoes are notorious for being susceptible to early and late blight. These fungal diseases can spread like wildfire. This is especially true in humid conditions. And guess what? Cucumbers can also be affected by blights. Although often different strains. Still, planting them together increases the overall risk of fungal issues. These can take hold in that part of your garden. It’s like putting two kids with runny noses in the same room. You’re just asking for germs to spread!

Heavy Feeders

Beyond the disease factor, potatoes are also really heavy feeders. They need a lot of nutrients. Particularly phosphorus and potassium. This develops those tasty tubers underground. Cucumbers, with their rapid vine growth and fruit production, are also quite hungry.

Planting them side-by-side creates intense competition for nutrients and water in the soil. The stronger, more established potato plants might just outcompete the cucumber vines. This leaves your cukes hungry and weak. Weak plants are more vulnerable to pests and diseases anyway. This creates a vicious cycle.

So, for the sake of both your potato and cucumber yields, it’s best to give them separate beds.

How to prevent blight in your cucumber patch: Avoid planting near potatoes. Trust me on this one. It’s a key part of avoiding bad companion plants for cucumbers.

4. Why is Fennel Bad for Cucumbers?

Answer: Fennel is bad for cucumbers because it releases allelopathic chemicals into the soil that specifically inhibit the growth of nearby plants, including cucumbers, leading to stunted growth.

Now, fennel is a fascinating plant, isn’t it? Its feathery fronds are wonderful. Its distinct anise flavor is too. But when it comes to companion planting, fennel is kind of a loner. It’s definitely on the list of what not to plant with cucumbers.

Understanding Allelopathy

This isn’t because it competes for water. Or attracts the same bugs. Nope. Fennel has a different trick up its sleeve. It’s called allelopathy. Allelopathy is when one plant releases natural chemicals into the soil that can stop other plants from growing well.

Fennel is known to release compounds into the soil. These can inhibit the growth of many other vegetables. This includes cucumbers. It can really put the brakes on your cucumber vines. This results in plants that stunt cucumber growth.

Because of this allelopathic effect, fennel is generally considered a plant harmful to cucumbers. It’s one of those antagonistic plants for cucumbers. It just doesn’t play well with others. My best advice? Give fennel its own dedicated spot. It won’t interfere with your precious cucumber patch. Or other sensitive veggies. It’s truly best grown in isolation.

How to avoid fennel’s negative impact: Grow fennel in a container or a separate bed away from other vegetables. This simple step in your cucumber garden planning can make a huge difference. It helps in avoiding bad companion plants for cucumbers. It ensures a healthy, productive garden.

5. Why is Mint Bad for Cucumbers?

Answer: Mint is bad for cucumbers because it is an incredibly aggressive spreader with a vigorous root system that will quickly overtake and steal resources like water and nutrients from less competitive plants like cucumbers.

Speaking of plants that don’t play nice, let’s talk about mint. You asked, “Is mint bad for cucumbers?” And the answer is a resounding yes, if not contained!

Aggressive Root System

Oh, mint! It smells divine. It’s amazing in drinks. But left unchecked in the garden, it’s a total bully. Mint is absolutely one of the worst plants for cucumbers. Why? Because it’s an incredibly aggressive spreader. Its roots will take over everything!

Planting mint near your cucumbers means it quickly starts overtaking and stealing resources. It’s like that friend who eats all the snacks. And drinks all the soda at your party. Not cool! The vigorous root system of mint will outcompete your cucumber vines. It fights for every last drop of water. It fights for every nutrient in the soil. This intense plant competition will definitely lead to plants that stunt cucumber growth.

Potential Flavor Impact

Some gardeners also believe that mint’s strong aroma can negatively impact the flavor of nearby vegetables. Although this is a bit more debated. But honestly, the sheer fact that it will try to take over your entire garden is reason enough. Keep it far away from your cucumbers. If you must grow mint, plant it in a container. This keeps its enthusiastic roots in check.

How to prevent mint from harming cucumbers: Always grow mint in a container to control its spread. It’s a crucial step in knowing which plants to keep away from cucumbers for successful cucumber companion planting.

6. Why are Brassicas Bad for Cucumbers?

Answer: Brassicas are bad for cucumbers because they are heavy feeders that compete with cucumbers for moisture and nutrients, and they attract shared pests like cabbage worms and aphids, increasing the risk of infestation.

Now, let’s look at the brassica family. This includes popular veggies like broccoli, cauliflower, and cabbage. While delicious in their own right, they are generally considered bad companion plants for cucumbers.

Resource Competition

There are a couple of reasons why they make the list of what should you not plant around cucumbers. Firstly, like many of the plants we’ve discussed, brassicas are relatively heavy feeders. They need a good amount of nutrients. This forms those big heads or leaves. Planting them near cucumbers means they’ll be competing for moisture and nutrients in the soil. This nutrient competition can leave your cucumber vines lacking the fuel they need. This impacts their ability to produce a bountiful harvest.

Shared Pest Attraction

Secondly, and perhaps more importantly, brassicas can attract some of the same pests that plague cucumbers. Think about cabbage worms. And aphids. These little critters love to munch on both brassicas and cucumber leaves and vines. Planting them together is like setting up a buffet for these pests. This increases the chances of a major infestation. This can damage or destroy your cucumber crop. It’s a classic case of shared pest attraction. So, keep your broccoli, cauliflower, and cabbage in a different part of the garden. This reduces the risk to your cucumbers.

How to reduce pest issues with cucumbers: Keep brassicas in a different part of the garden. It’s a smart move in your overall cucumber garden planning.

7. Why are Black Walnut Trees Bad for Cucumbers?

Answer: Black walnut trees are bad for cucumbers because they release a toxic chemical called juglone that is harmful to cucumber growth, causing wilting, yellowing, and potentially death.

Okay, this one is a bit different. It involves a tree. Not just another garden vegetable. But if you have a black walnut tree anywhere near your garden, you absolutely need to know something. It’s a major plant harmful to cucumbers.

What is Juglone?

Black walnut trees produce a toxic chemical called juglone. Juglone is a natural compound found in black walnut trees. It can be toxic to many other plants. This compound is released into the soil. It comes from the tree’s roots, nuts, and leaves. This happens as they decompose. It’s a natural defense mechanism for the tree. It helps it reduce plant competition from other species.

Impact on Cucumbers

Unfortunately, many plants are highly sensitive to juglone. And cucumbers are one of them. Exposure to juglone can cause wilting. It can cause yellowing. Ultimately, it can cause death in cucumber plants. It has a significant impact on cucumber growth.

The juglone toxicity zone extends out from the drip line of the black walnut tree. Sometimes even further. This is because the roots can spread quite a distance underground. So, if you have a black walnut tree, choose a garden spot well away from its reach. How to protect cucumbers from black walnut trees: Plant cucumbers well outside the drip line of the tree. It’s a critical factor in cucumber garden planning if you have these trees around. Avoiding the juglone threat is essential. It prevents this kind of damage to your cucumber vines.

Quick Look: 7 Worst Cucumber Companions

Here’s a quick summary of the plants you should avoid planting near your cucumbers and why:

• Cucurbits (Squash, Melons, Pumpkins): Compete heavily for resources and share common pests/diseases.
• Aromatic Herbs (Sage, Rosemary): Can stunt growth and have different moisture needs.
• Potatoes: High risk of spreading blight diseases and compete intensely for nutrients.
• Fennel: Releases allelopathic chemicals that inhibit cucumber growth.
• Mint: Aggressive spreader that will outcompete cucumbers for resources.
• Brassicas (Broccoli, Cauliflower, Cabbage): Compete for food and attract shared pests.
• Black Walnut Trees: Release a toxic chemical (juglone) harmful to cucumber growth.

Other Problematic Plants and Considerations: What Else to Watch Out For?

Beyond the main offenders, there are a few other plants. They can cause issues for cucumbers. Or at least require careful consideration. Knowing about these helps you make the best decisions for your garden layout. It helps you avoid other potential bad companion plants for cucumbers.

Are Tomatoes Bad for Cucumbers?

Answer: While not strictly “bad” in all cases, planting tomatoes and cucumbers together can be problematic due to competition for resources and shared disease susceptibility.

Ah, tomatoes! Everyone wants to know if they can plant tomatoes and cucumbers together. It’s a common question! The answer is… it’s complicated. While they aren’t the worst combination ever, they aren’t exactly the best of friends either.

Resource Competition and Shared Diseases

One issue is competition for resources. Both plants are heavy feeders. They need consistent watering. This is especially true when they’re producing fruit. Planting them too close can lead to them competing for those vital nutrients and water. Plus, they can share some diseases. Like verticillium wilt and fusarium wilt. While cucumbers are generally less susceptible than tomatoes, the risk of disease spread is still there.

Vining Habits

Also, consider their vining habits. Both cucumbers and indeterminate tomatoes can grow quite large. They can be sprawling. If not properly trellised or managed, they can easily overwhelm each other. This blocks sunlight. It reduces air circulation. This further encourages disease. So, while not a hard “no,” planting tomatoes and cucumbers together requires careful management. It needs plenty of space. It needs vigilance for shared issues.

How to manage planting tomatoes and cucumbers together: Ensure ample space, proper trellising, and monitor for shared diseases. It’s often easier to give them separate areas in your cucumber garden planning.

Why are Jerusalem Artichokes Bad for Cucumbers?

Answer: Jerusalem artichokes are bad for cucumbers because their incredibly vigorous root systems create intense root competition for space, water, and nutrients.

Jerusalem artichokes are fantastic plants. They produce tasty tubers. They have tall, sunflower-like stalks. However, they are also known for their incredibly vigorous root systems. These roots spread far and wide. They can create intense root competition with nearby plants.

Planting cucumbers near Jerusalem artichokes means the cucumber roots will have to fight for space. They’ll fight for water. They’ll fight for nutrients. This can lead to weaker cucumber plants. It can mean a reduced harvest.

They are definitely an antagonistic plant for cucumbers when planted in close proximity. Give Jerusalem artichokes their own space. Their spreading roots won’t bother your other vegetables there.

How to avoid root competition with Jerusalem artichokes: Plant them in an isolated area away from cucumbers.

Why is Rue Bad for Cucumbers?

Answer: Rue is generally considered an unfriendly neighbor for cucumbers because some gardeners report that planting it nearby can negatively influence the flavor of the cucumbers.

Rue is an herb with a strong scent. It’s sometimes used in gardens. But it’s generally considered an unfriendly neighbor for many vegetables. This includes cucumbers. While not as well-documented as the allelopathic effects of fennel, some gardeners report something.

Planting rue nearby can negatively influence the flavor of cucumbers. It’s a risk I personally wouldn’t take. Not after putting in all the effort to grow delicious cukes! It’s another one of those plants to keep away from cucumbers. Just to be safe.

How to prevent flavor alteration in cucumbers: Avoid planting rue nearby.

Why are Hops Bad for Cucumbers?

Answer: Hops are bad for cucumbers because they are incredibly vigorous climbers whose rapid growth can easily overtake and literally strangle less aggressive cucumber vines, competing fiercely for vertical space and sunlight.

Finally, let’s talk about hops. If you happen to be growing hops for brewing. Or for ornamental purposes. Keep them far away from your cucumber patch. Hops are incredibly vigorous climbers. Their vines grow rapidly. They can easily overtake less aggressive plants. Like cucumbers. They can literally strangle vines. They will compete fiercely for vertical space.

And sunlight. This leaves your cucumber vines in the shade. They won’t be able to thrive. Hops are definitely a plant harmful to cucumbers. This is due to their aggressive growth habit.

 How to protect cucumber vines from hops: Keep hops far away from your cucumber patch.

Summary of Other Problematic Plants

These additional plants might not be in the top 7, but they can still cause headaches for your cucumbers due to competition, potential disease sharing, or aggressive growth habits. Being aware of them helps you make the best choices for your garden layout.

Optimizing Your Garden: Setting Up for Cucumber Success

So, now that we’ve covered the no-gos, let’s shift gears. Let’s talk about how to set your cucumbers up for the best possible outcome. Avoiding bad companion plants for cucumbers is just one piece of the puzzle. But implementing smart strategies is where the magic really happens. This leads to a bountiful harvest. This section is all about the what to do instead. It ensures your cucumber plants thrive!

Imagine stepping into your garden and seeing lush, vigorous cucumber vines bursting with life. Picture yourself effortlessly picking basketfuls of crisp, juicy cucumbers, perfect for salads, pickles, and refreshing summer snacks! That’s the kind of abundant success you can unlock with smart garden planning.

Understanding Cucumber Needs: Sun, Soil, and Sips

First off, you’ve got to know what makes cucumbers happy. They are sun-worshippers. They need at least 6-8 hours of direct sunlight daily for optimal growth and fruit production. They also crave rich, well-draining soil. It should be loaded with organic matter. Think compost, compost, and more compost! This gives them the essential nutrients they need to grow strong vines and produce lots of fruit.

And remember how I said they were water hogs? It’s true! Cucumbers need consistent moisture, especially when it’s hot and dry. Uneven watering can lead to bitter fruits or frustrating issues like blossom end rot. So, make sure your watering schedule is on point to keep those cukes hydrated and happy! Getting these fundamental needs right is the foundation of successful cucumber companion planting. This is true whether you’re adding good neighbors or just keeping the bad ones away.

The Upside of Good Neighbors (Briefly!)

While this article is all about who not to plant, it’s worth a quick mention. There are also fantastic companion plants for cucumbers that can actually help them thrive! Plants like dill, mint (in a container!), and marigolds can actually help deter pests, acting as natural guardians for your vines. Beans and peas can add valuable nitrogen to the soil, a nutrient cucumbers really appreciate for leafy growth.

And beautiful flowers like borage can attract essential pollinators, ensuring you get plenty of fruit set. So, once you know which plants to keep away from cucumbers, you can start thinking about adding some beneficial buddies to create a truly harmonious and productive garden ecosystem!

Crop Rotation and Garden Planning for Success

Beyond companion planting, another crucial strategy for garden health and maximizing your harvest is crop rotation. This avoids issues like disease spread and pest attraction that can build up in the soil over time. Don’t plant cucumbers (or any other cucurbits) in the same spot year after year. This helps break the cycles of pests and diseases that can overwinter in the soil, giving your new plants a clean start. Aim to rotate your cucumber patch to a different part of the garden every 2-3 years for the best results.

How to improve garden health and prevent disease: Practice crop rotation and avoid planting cucumbers in the same spot annually.

Overall garden planning is super important for cucumber success. Before you even put a seed in the ground, take some time to sketch out your garden layout. Think about where the sun hits throughout the day, where water tends to collect, and crucially, which plants you need to keep separated to avoid those problematic pairings. This proactive approach combines your knowledge of what should you not plant around cucumbers with good basic gardening practices, giving you your best bet for a fantastic, problem-free cucumber harvest.

Frequently Asked Questions (FAQs) on What Not to Plant with Cucumbers: 7 Worst Companion Plants to Avoid

Conclusion: Mastering Companion Planting for Cucumber Glory

Alright, garden friends, we’ve covered a lot of ground today! We’ve dug into the nitty-gritty of what should you not plant around cucumbers. We’ve also discussed why avoiding these bad companion plants for cucumbers is so darn important. From the competitive cucurbit cousins (with a nod to the Three Sisters!) and the bossy aromatic herbs to the blight-prone potatoes, the solitary fennel, the aggressive mint, the resource-hogging brassicas, and the downright toxic black walnut trees, knowing these potential pitfalls is your first step towards a thriving cucumber patch.

Remember, successful cucumber companion planting isn’t just about finding the perfect plant pals. It’s also crucially about knowing which plants to keep away from cucumbers. By understanding the reasons behind these antagonistic relationships – whether it’s plant competition for resources, shared cucumber pests and diseases, allelopathy, or just plain aggressive growth – you can make informed decisions for your cucumber garden planning.

Ultimately, mastering companion planting, including knowing the worst plants for cucumbers, is a key ingredient. It helps you achieve a truly bountiful harvest. Combine this knowledge with good basic practices. Provide ample sun, water, and nutrient-rich soil. Incorporate crop rotation. You’ll be well on your way to picking armloads of crisp, delicious cucumbers all season long.

So, take a good look at your garden layout. Consider the neighbors you’ve planted. Or are planning to plant! Make those strategic adjustments. Your cucumbers will thank you for it!

Quick Look: 7 Worst Cucumber Companions

1. Cucurbits: Compete for resources, share pests/diseases.
2. Aromatic Herbs (Sage, Rosemary): Stunt growth, different moisture needs.
3. Potatoes: Blight risk, intense nutrient competition.
4. Fennel: Allelopathic chemicals inhibit growth.
5. Mint: Aggressive spreader, chokes out cucumbers.
6. Brassicas: Compete for food, attract shared pests.
7. Black Walnut Trees: Release toxic juglone.

Got any experiences with these bad companion plants for cucumbers? Or maybe you’ve discovered another plant that cucumbers just don’t jive with? Share your thoughts and questions in the comments below! Let’s learn from each other. Let’s grow the best gardens possible!