Incompatible Plants: 20 Plants & What They Can’t Grow With

Both, novice and experienced gardeners favor companion planting, as, despite the numerous other benefits, it is an excellent way to grow maximum food in minimal space and reduce competition between plants.

Companion planting has a long history, as confirmed by the Cornell University’s Horticultural Factsheet:

“Naturalists have known about these properties of plants for thousands of years. For example, about 2,000 years ago the Roman agriculturalist, Varro, declared “Large walnut trees close by, make the border of the farm sterile.”

Chemicals in oak leaves retard the development of insects that feed on them… Alfalfa and clover enrich the soil with nitrogen that they capture from the air.

Certain trees move groundwater to the soil surface where shallow-rooted plants can grow even under droughty conditions. Groups of plants which grow well together are called “companions. “

This practice of planting more plants together is for a mutual benefit, such as improved growth and quality.

Vegetable Gardening Life lists some of the other benefits of this practice:

“ --  Shelter -- larger plants protect others from wind or too much sun.

--    Support -- Some vegetables can be used as physical supports for others. As an example, pole beans planted with corn use the corn as a trellis.

--    Beneficial Insects -- attracting beneficial insects such as bees help spread pollen.

--    Soil Improvement -- some vegetable plants improve soil conditions for other plants. For example, members of the legume family (beans etc.) draw nitrogen from the atmosphere and add it to the soil around them.

--    Decoy Plants -- there are plants that emit odors that aid in masking the odors of insect-desirable vegetable plants.”

Yet, sometimes, no matter how hard to try to stimulate the proper growth of your plants in the garden, the results are far from what you have expected.

Despite being competitive between each other, plants can be incompatible and thus respond to different environmental needs, or might even attract pests that harm the one next to it.

When it comes to avoiding such issues, Gardening Know How gives several basic rules of thumb:

“ First, check that your garden plants are all about the same size and have the same light requirements. Planting very tall plants like tomato next to bush beans, for example, is a very bad idea since the tomatoes will very likely shade out the beans.

When planting taller and shorter plants together, make sure that the shorter plants are spaced far enough away and orientated so the sun will shine on them during the day.

Many gardeners solve this problem by putting the shortest plants in their own row on the edge of the garden or planted as a border planting. “

They also add:

“Plants that need a lot of water will cause those water haters nearby a great deal of discomfort; the same goes for fertilizer. It’s always a good idea to plant things with similar nutritional and water needs together unless they’re fiercely competitive.

Even then, you can often compensate by spacing them extra wide and providing enough fertilizer and water for both types of plants. “

Moreover, keep this in mind:

“ Allelopathic plants have the capability to chemically impede the vital systems of competing plants. These plants are usually weeds, but many landscapes and crop plants have been observed leaving behind allelopathic chemicals.

Plant scientists are using these observations to develop better methods of weed control for farms and gardens alike.”

Seasoned gardeners, helped by their experience, have compiled a list of incompatible plants that can help you grow popular vegetables without any issues and stimulate their development, having in mind the requirements of each group of plants in your garden. Read on:

1. Potatoes – Potato plants benefit from the company of catnip, marigolds, and nasturtium, as well as corn, beans, peas, and cabbage family vegetables. Yet, their enemies include spinach, tomatoes, cucumbers, pumpkin, squash, and sunflower.

2. Squash – While it gets along well with onions, beans, and radishes, and insect-repellant herbs and protective plants like mint and catnip marigold and nasturtium, squash does not like the company of pumpkins and potatoes.

3. Cucumbers – They are incompatible with aromatic herbs like rosemary, sage, marjoram, and basil, but grow well among beans and peas, as well as almost all vegetables of cabbage and nightshade families.

4. Kale – It enjoys the protection of mint family herbs, onions, dills, and garlic, but it detests basil and strawberries.

5. Carrots – Carrots thrive beside legumes such as beans and peas and nightshade family vegetables, but on the other hand, they can grow near root vegetables like radish, onion, and leeks, as well as low growing plants like lettuce and parsley.

6. Lettuce – Even though lettuce is similar to cabbage, it belongs to the daisy family, and is compatible with cauliflower and kale, but is intolerant of onions, garlic, and all Allium family members.

7. Tomato – Do not plant tomatoes together with corn, cabbage family members, peppers, eggplant, and potatoes.

8. Garlic – The pungent smell of garlic keeps pests away, so plant it near tomatoes, radishes, roses, and cabbage family vegetables.

However, you should not grow garlic near peas, asparagus, and beans, and make sure their roots do not share the same space.

9. Melon – You can grow melons near corn, tomatoes, and sunflowers, but are incompatible with potatoes.

10. Onion – It is an excellent companion to members of the cabbage family members and nightshade vegetables, as well as beets and carrots. Yet, avoid planting onions near asparagus, and legume family members.

11. Cabbage – You will benefit from growing cabbage near herbs like garlic, dill, celery, onions mints, thyme, and rosemary, as they will protect it from pests. On the other hand, avoid planting it near basil and tomato.

12. Peppers – Peppers are incompatible with fennel and kohlrabi, but have no problems growing beside tomatoes, potatoes, and eggplant.

13. Asparagus – Do not grow garlic and fennel around your asparagus, but feel free to surround it with nasturtiums and marigolds, as well as herbs like basil and parsley.

Asparagus and garlic compete for the same nutrients, as well as all members of the onion family, and fennel is a bad companion to numerous veggies.

14. Spinach – Spinach likes being planted around legumes like beans and peas, strawberries, and most cabbage family veggies, but it is incompatible with potatoes.

15. Beans – Members of the cabbage and onion families should not be grown near beans, while the latter can grow perfectly well in between other veggies, especially spinach, cucumber, corn, and potato.

16. Strawberry – Plant bush beans planted near strawberries, as well as sage, thyme, and onions, but keep them away from the pest-prone cabbage family vegetables.

17. Corn – Corn thrives beside tomatoes, as they are both heavy feeders. On the other hand, it is compatible with beans and squash.

18. Rosemary – Plant rosemary around cruciferous veggies, but keep them away from cucumbers.

19. Broccoli – Broccoli is compatible with aromatic herbs, like the members of the allium and mint families. Yet, it does not like basil, peas, tomatoes, and strawberries.

20. Cauliflower – Plant cauliflower near aromatic herbs and onion family plants to prevent pests, but keep it away from cabbage, tomatoes, and beans.

Remember that these guidelines are not a precise science, as the yield and growth of your plants in the garden mostly depend on the type of soil, nutrients, availability, weather and growing seasons.

Plants with similar needs will still compete for nutrients in the case of water and nutrient deficiencies in the soil.

Yet, experienced gardeners will give the needed close observation and attention to the patches, and find what is best for them and discover the beneficial companionships and incompatibilities.