When planning your garden, knowing what not to plant together is just as crucial as knowing what to plant. Certain plant combinations can hinder growth, attract pests, or deplete soil nutrients for neighboring plants, leading to a less bountiful harvest. Understanding these companion planting principles helps create a healthier, more productive garden ecosystem.

Why Companion Planting Matters in Your Vegetable Garden

Companion planting is an age-old gardening technique that leverages the natural relationships between different plants. It’s about creating a symbiotic environment where plants benefit each other. This can involve deterring pests, attracting beneficial insects, improving soil fertility, or even enhancing the flavor of certain crops.

Avoiding Negative Interactions: What to Keep Apart

Just as some plants are friends, others are rivals. Planting incompatible species too close can lead to a variety of problems. These issues can range from stunted growth and increased susceptibility to diseases to attracting specific pests that target one or both plants.

The Case of the Alliums: Onions, Garlic, and Their Neighbors

Alliums, such as onions, garlic, and leeks, are powerful plants. They release compounds that can deter many common garden pests, like aphids and slugs. However, these same potent compounds can negatively impact the growth of certain vegetables.

• Legumes (Beans and Peas): Alliums can inhibit the nitrogen-fixing bacteria on the roots of beans and peas. This reduces their ability to enrich the soil, which is their primary benefit.
• Brassicas (Cabbage, Broccoli, Kale): While alliums can deter some pests that bother brassicas, they can also stunt the growth of these leafy greens.

Root Vegetables and Their Space

Root vegetables often require specific soil conditions and nutrients. Planting them next to plants with similar needs can lead to competition.

• Carrots and Parsnips: These root vegetables are from the same family (Apiaceae). They can attract similar pests, like the carrot rust fly, and compete for the same soil nutrients, leading to smaller roots for both.
• Potatoes and Tomatoes: Both are members of the nightshade family. They are susceptible to the same diseases, such as blight. Planting them together can increase the risk of widespread infection.

Leafy Greens and Their Companions

Leafy greens, like lettuce and spinach, can be sensitive to their surroundings.

• Fennel: This aromatic herb is known to inhibit the growth of many common garden plants, including beans, peas, and lettuce. It’s often best to give fennel its own space.
• Parsley and Mint: While not strictly detrimental, planting these herbs too close to other vegetables might encourage them to bolt (go to seed) prematurely due to competition for resources.

Understanding Plant Families and Their Needs

A good rule of thumb in gardening is to be mindful of plant families. Plants within the same family often share similar nutrient requirements and are susceptible to the same pests and diseases. This makes them poor companions for each other.

Common Plant Families to Watch Out For

• Nightshades (Solanaceae): Includes tomatoes, potatoes, peppers, and eggplant. Avoid planting these close together.
• Brassicas (Brassicaceae): Includes cabbage, broccoli, cauliflower, kale, Brussels sprouts, and radishes. Keep members of this family separated from each other and from tall, heavy feeders.
• Legumes (Fabaceae): Includes beans, peas, and lentils. They are nitrogen fixers and generally good companions, but avoid planting them near alliums.
• Cucurbits (Cucurbitaceae): Includes cucumbers, squash, melons, and pumpkins. They can be heavy feeders and require ample space.

Practical Examples of What NOT to Plant Together

Let’s look at some specific, common garden scenarios where you should avoid planting certain vegetables next to each other.

Tomato Troubles: Avoiding Bad Neighbors

Tomatoes are a garden staple, but they have particular dislikes.

• Tomatoes and Broccoli: Broccoli is a heavy feeder and can deplete the soil of nutrients that tomatoes need.
• Tomatoes and Corn: Corn can attract the corn earworm, which also readily attacks tomatoes.

Bean Blunders: What to Keep Away from Beans

Beans are nitrogen fixers, making them beneficial for many plants. However, they have a few nemeses.

• Beans and Onions/Garlic: As mentioned, alliums interfere with the nitrogen-fixing capabilities of beans.
• Beans and Kohlrabi: Kohlrabi can stunt the growth of bush beans.

Cucumber Concerns: Space and Sensitivity

Cucumbers need space and can be sensitive to certain companions.

• Cucumbers and Potatoes: Potatoes can attract blight, which can spread to cucumbers.
• Cucumbers and Aromatic Herbs (like Sage): Some strong-smelling herbs can deter beneficial insects that help pollinate cucumbers.

Creating a Balanced Garden Ecosystem

The goal of understanding what not to plant together is to foster a balanced garden ecosystem. This involves thoughtful planning that considers the needs of each plant and how they interact with their neighbors.

Beneficial Relationships to Encourage

While avoiding negative pairings, actively seek out beneficial ones. For instance:

• Marigolds: Known to deter nematodes and other soil-borne pests.
• Basil: Can repel flies and mosquitoes, and some gardeners believe it improves tomato flavor.
• Nasturtiums: Act as a trap crop for aphids, drawing them away from other vegetables.

By strategically planting these beneficial companions, you can further enhance the health and productivity of your garden, even when dealing with some incompatible pairings.

People Also Ask

### Why shouldn’t I plant potatoes and tomatoes together?

Potatoes and tomatoes are both members of the nightshade family and share susceptibility to diseases like blight. Planting them in close proximity significantly increases the risk of these diseases spreading rapidly through your garden, potentially destroying both crops. It’s best to rotate their planting locations each year.

### Can I plant carrots near onions?

Yes, carrots and onions are generally considered good companions. Onions can help deter the carrot rust fly, a common pest that targets carrots. The strong scent of onions masks the smell of carrots, making them less attractive to this pest. Both also have different nutrient needs, reducing competition.

### What plants should not be planted next to corn?

Avoid planting tomatoes and corn together. Corn can attract the corn earworm, which also readily attacks tomatoes. Additionally, corn is a heavy feeder and can deplete the soil of nutrients needed by other plants. It’s also often advised to keep beans away from corn if you are planting them in large quantities, as they can compete for sunlight.

### Is it bad to plant peppers and cucumbers together?

Generally, peppers and cucumbers can be planted near each other without significant issues. They belong to different plant families and have different primary pest and disease vulnerabilities. However, ensure they have adequate space and access to sunlight, as overcrowding can lead to problems for any garden plant.

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