Dahlias have some of the most beautiful flowers. Your garden will look much more colorful and charming if you plant them.
But sadly there are many plants and flowers that don’t go well with dahlias. They fight over food, attract pests or just make it difficult to grow.
So if you’re planning on growing dahlias it’s best to keep these plants out of your garden. I’ll go through 12 plants you shouldn’t plant near your dahlias and why.
Why Compatibility Matters in the Garden
Choosing the right plants to go with one another is important for a successful garden. There are plants that grow well together and help each other out.
But others do the opposite – take all the nutrients from the soil, block the sunlight or even bring in insects that can cause problems.
Knowing which to avoid can help you grow healthier dahlias.
1. Tomatoes
Tomatoes and dahlias may seem like they’d get along but they actually fight over nutrients and attract pests.
Why Tomatoes are a Problem
- Nutrient Competition: Both need a lot of nutrients, especially phosphorus and potassium, which means the soil gets depleted of them.
- Pest Attraction: Tomatoes attract aphids, whiteflies and spider mites, which can then spread to and harm dahlias.
2. Cucumbers
Cucumbers grow quickly and can make dahlias struggle by taking up the space they need.
Why Cucumbers are a Problem:
- Growth: Cucumbers grow well and if allowed to do so will block dahlias from getting the sun they need.
- Pest Issues: Cucumber beetles and powdery mildew will attack cucumbers and then could spread to and affect dahlias too.
3. Peppers
Peppers and dahlias don’t grow well together because of problems with pests and a need for a lot of nutrients.
Why Peppers are a Problem:
- Nutrient Depletion: Peppers need lots of nitrogen and potassium which can make any dahlias struggle.
- Pest Concerns: Aphids and spider mites often affect peppers and can spread to dahlias.
4. Roses
Roses and dahlias look great but they struggle when planted together.
Why Roses are a Problem:
- Competing for Nutrients: Both need fertilized and rich soil which can cause deficiencies for one another.
- Pest Problems: Aphids, mites and fungal diseases happen to roses and can then spread to dahlias.
5. Corn
Corn take up a lot of space and so doesn’t work well with dahlias.
Why Corn is a Problem:
- Shade Issues: Corn grows tall and so blocks the sun from reaching dahlias.
- Heavy Feeding: Corn takes lots of nutrients from the soil, leaving little for dahlias.
6. Fennel
Fennel is a poor match for many plants, including dahlias.
Why Fennel is a Problem:
- Allelopathic Effects: Fennel releases substances that stop plants near to it from growing.
- Pest Attraction: Fennel attracts pests like aphids and caterpillars which can harm dahlias.
7. Carrots
Carrots may not appear to be an issue but they can upset dahlias.
Why Carrots are a Problem:
- Root Competition: Carrots have deep roots that clash with dahlias roots.
- Pest Concerns: Carrot flies can spread to others flowers, including dahlias.
8. Beans
Beans can fight over space and nutrients when planted near to dahlias.
Why Beans are a Problem:
- Climbing Growth: Beans can block light from the getting tk dahlia’s and smother them as they grow.
- Nutrient Fixation: Beans may add nitrogen to the soil but dahlias like there to be a better balance of nutrients.
9. Mint
Mint is an grows aggressively and doesn’t work well with dahlias.
Why Mint is a Problem:
- Invasive Growth: Mint spreads very quickly and will take over your garden beds.
- Allelopathic Effects: It releases chemicals that can stop dahlia growing.
10. Sunflowers
Sunflowers can make it hard for sunflowers to grow properly.
Why Sunflowers are a Problem:
- Shade Issues: Sunflowers grow very tall and block the light from reaching dahlias.
- Soil Competition: They have deep roots that absorb a lot of water and nutrients.
11. Zucchini
Zucchini plants are large and aggressive in the way they grow so bad next or near to dahlias.
Why Zucchini is a Problem:
- Space Hog: Zucchini grow wide and leave little room for dahlias to grow.
- Pest Issues: Squash bugs and powdery mildew can spread to dahlias.
12. Basil
While basil can help some plants it’s really not good for dahlias.
Why Basil is a Problem:
- Nutrient Competition: Basil fights over nutrients, especially phosphorus.
- Fungal Issues: Basil can develop fungal diseases that then spread to dahlias.
Good Companions for Dahlias
Some plants work well with dahlias and can help them to grow.
- Lavender: Keeps away pests and attracts pollinators that benefit dahlias.
- Salvia: Brings in beneficial insects and doesn’t fight for nutrients.
- Cosmos: Looks good alongside dahlias without overcrowding them.
Tips for Successful Companion Planting
- Choose Plants Wisely: You want plants that don’t fight over the same nutrients.
- Look for Pests: Keep an eye on plants that might attract insects that will do damage to dahlias.
- Provide Enough Space: Make sure your plants have room to grow without blocking light to each other.
Final Thoughts
Planning what your garden is going to have in it beforehand will make sure all your plants and flowers do well, dahlias included. So don’t plants together with ones that are incompatible with them and you can then be far more confident you’ll have success in your garden.
Would others from the carrot family be good companions? I am thinking of dill, ammi, and corriander.