Plants You Should Not Grow Near Tomatoes
Knowing which plants you should not grow near tomatoes is just as important as choosing good companions. Some plants compete for nutrients, attract the same pests, or increase the risk of disease — all of which can seriously reduce tomato yields and plant health.
Keter Manor Outdoor Apex Double Door Garden Storage Shed (6 x 8ft)
A durable and stylish beige and brown garden storage shed perfect for storing garden tools, equipment, bikes, and outdoor essentials. Weather-resistant, low maintenance, and ideal for any garden or allotment setup.
Vegetable Plants & Seedlings
Browse Plants
All-Purpose Compost & Soil Improvers
View Compost
Plant Feed & Fertiliser for Strong Growth
Shop Fertiliser
⭐ Recommended Products — Tomatoes & Growing Essentials
• Tomato Seed Collection (Garden & Greenhouse Varieties)
A mix of popular tomato seeds — including salad and beefsteak types — perfect for sowing indoors early and planting out when warm.
👉 Click here to see top options
• Tomato Plants (Ready-Grown)
Save time with healthy young tomato plants — excellent if you prefer planting established plants rather than starting from seed.
👉 Click here to see top options
• Tomato Support Cages & Stakes
Helps keep vines upright, improving air circulation and reducing disease — essential for healthy growth and easier harvesting.
👉 Click here to see top options
• Tomato Feed & Fertiliser
Formulated with high potassium to support strong flowering and fruiting — use regularly through the growing season for bigger, juicier tomatoes.
👉 Click here to see top options
• Tomato Grow Bags / Containers
Ideal for patios, balconies, or greenhouse growing — provides good drainage and space for roots to develop big, productive plants.
👉 Click here to see top options
Avoiding poor companions helps tomatoes grow stronger, stay healthier, and produce better-quality fruit.
Why Some Plants Are Bad Neighbours for Tomatoes
Tomatoes are heavy feeders and are prone to pests and diseases. The wrong neighbouring plants can:
- Compete for nutrients and water
- Share pests and soil-borne diseases
- Reduce airflow and increase humidity
- Suppress tomato growth
Understanding these risks makes it easier to plan a productive garden layout.
Potatoes
Potatoes are one of the worst companions for tomatoes.
Why to avoid them:
- Share the same diseases, including blight
- Attract similar pests
- Compete heavily for nutrients
Planting tomatoes near potatoes significantly increases the risk of disease spreading between crops.
Peppers and Aubergines
Peppers and aubergines belong to the same plant family as tomatoes.
Problems include:
- Shared pests and diseases
- Increased disease pressure in soil
- Competition for nutrients
While tempting to group them together, it’s far safer to rotate these crops instead.
Brassicas (Cabbage, Cauliflower, Broccoli)
Brassicas are not ideal neighbours for tomatoes.
Why they clash:
- Heavy nutrient competition
- Can stunt tomato growth
- Prefer different soil conditions
Both crops grow better when given their own space.
Fennel
Fennel is a poor companion for most vegetables, including tomatoes.
Reasons to avoid fennel:
- Releases substances that inhibit growth
- Suppresses nearby plants
- Performs best grown alone
Keep fennel well away from tomato beds.
Corn (Sweetcorn)
Sweetcorn may seem harmless, but it causes problems.
Issues include:
- Competes for water and nutrients
- Attracts pests that also attack tomatoes
- Creates excessive shade
Tomatoes require full sun and airflow, which corn can block.
Walnuts and Walnut Trees
Tomatoes should never be planted near walnut trees.
Why this is a problem:
- Walnuts release juglone, which is toxic to tomatoes
- Causes wilting and poor growth
- Can kill young tomato plants
Even fallen leaves and roots can affect soil quality.
Sunflowers
Sunflowers can negatively affect tomatoes when planted too close.
Potential problems:
- Compete heavily for nutrients
- Cast dense shade
- May release growth-inhibiting compounds
While beneficial for pollinators, they should be planted at a distance.
Dill (When Mature)
Young dill is fine, but mature dill can cause issues.
Why mature dill is a problem:
- Competes for nutrients
- Can inhibit tomato growth once flowering
- Attracts pests if overcrowded
If growing dill, harvest early or plant it elsewhere.
Overcrowded Root Crops
Large root crops grown too closely can interfere with tomatoes.
Examples include:
- Large parsnips
- Overgrown beetroot
- Dense turnip plantings
Crowding reduces airflow and root space, increasing disease risk.
Common Mistakes When Pairing Tomatoes
- Grouping all nightshade crops together
- Overcrowding beds
- Ignoring airflow and sunlight
- Assuming all vegetables make good companions
Spacing and diversity are key to healthy tomato plants.
What to Do If You’ve Already Planted Them Together
If tomatoes are already growing near poor companions:
- Increase spacing where possible
- Improve airflow by selective pruning
- Monitor closely for pests and disease
- Consider relocating container-grown plants
Early intervention can reduce negative effects.
Final Thoughts
Avoiding the wrong plants near tomatoes can make a dramatic difference to plant health and harvest size. Potatoes, peppers, brassicas, fennel, and other poor companions increase disease risk, competition, and stress.
For best results, give tomatoes space, airflow, and neighbours that support rather than hinder their growth. Careful planning leads to healthier plants and better-tasting tomatoes all season long.