Posted on 22 May 2008 by

Companion Planting Part 2: The Arch-Enemies of Tomatoes

By Vanessa Richins

Recently we learned about the friends of tomatoes.

This time we turn attention to the foes – these are the plants that you don’t want to grow anywhere near your tomatoes.

Corn: Corn and tomatoes have an enemy in common. Whether you know it as the tomato fruitworm or the corn earworm, it’s bad, bad news. These 1.5-2″ monsters chew their way through your tomatoes, corn, and a host of other plants.

Dill: It’s strange….when dill is young, it actually enhances tomato growth and health. Once it is mature, however, the opposite is true and it will stunt tomato growth.

Potatoes: Remember how there was a great potato famine in 19th century Ireland? It was caused by a fungal disease called late blight. The fungus spreads and rots the potato. Unfortunately for us, tomatoes and the other members of the nightshade family can also be affected. The fungus can overwinter, so don’t plant tomatoes this year if you had infected potatoes last year. Both can also get another fungal disease- early blight.

Black walnut trees: Black walnut trees inhibit growth for all plants, but this is especially true for tomatoes and other nightshade family plants.

Fennel: This plant will interfere with tomato growth….alas for tomato/fennel recipes.

The family: The nightshade and Brassica families don’t like each other. Members include cabbage, cauliflower, broccoli, brussel sprouts, and kohlrabi. These will inhibit growth in your tomatoes.

Other potential foes include rosemary, apricots, and strawberries.

Are there any other combinations that have gone wrong in your experience?

18 Responses to “Companion Planting Part 2: The Arch-Enemies of Tomatoes”

  1. deb Says:

    Good information for those of us with a little garden.

  2. Amy Says:

    What a great, informative post, and just at the right time for me. I had no idea certain things shouldn’t be planted near tomatoes.

  3. Nancy Bond Says:

    Who knew? Thanks for the info!

  4. our friend Ben Says:

    Thanks, Vanessa! Another great post! Gardening is a lot more arcane that it seems, isn’t it? No wonder it’s more art than science!

  5. plantgirl Says:

    Great post – very helpful – now I know not to plant broccoli by my tomatoes!!
    ~plantgirl of

  6. Rees Cowden Says:

    Hey thanks for the good information. I’m all for using biological controls and I never realized the extent of the affect of plant combinations. I wonder bet there are similar realtionships in the ornamentals too.

  7. Deb Ng Says:

    I harvest my own marigold seeds every year and use a good deal of them to plant in the vegetable garden to keep away the pests.

  8. Urban Garden Casual »  This Week in Urban Gardens Says:

    […] urban garden plots can be small and tight. For those of us who love tomatoes, Vanessa Richins at Tomato Casual, tells us about tomatoes’ top arch enemies in the garden when it comes to companion […]

  9. Vanessa Richins Says:

    Thanks everyone…I think it’s amazing how different plants can affect each other so drastically!

  10. Jane Marie Says:

    I have both fennel and rosemary in the area where I grow tomatoes. I’ve never had a problem. Maybe they are not close enough.

  11. Vanessa Richins Says:

    Interesting…Jane Marie…that very well could be true. You may have just gotten lucky. Who knows? I visited many websites that mentioned those combinations as bad, but I am glad it is working out for you so far.

  12. Chuck N. Says:

    I’ve always heard the bit about the brassicas. Despite that, I planted two cherry tomatoes, a husky red and a sweet 100 right next to a row of brussels sprouts. The husky red is about six feet tall and the sweet 100 is at least 12 feet. They are both cranking out little red juice bombs faster than we can eat them. So, I’m not sure about the validity of the brassica claim. I don’t see any inhibition at all. OH! I also have an unknown variety of bell pepper planted next to them, showing no ill effects at all.

  13. claudia Says:

    In my experience FENNEL is a terrible foe for all crops including tomatoes. I planted rapini plants in october next to fennel and nothing came up until I harvested the entire fennel patch. one week later there were heaps of rapini to harvest. I doubt I will repeat the mistake a third time. Fennel only at the supermarket.

  14. Archangel Says:

    I’m a farmer and gardner. Companion planting is the key to good organic crops and in the case of tomatoes, marigolds and basil do more than bring in beneficial insects and deter others, they also provide chemicals in their root system that benefit tomato plants. Moreover, particularly with basil, its strong odor provides a barrier which confuses and stand off many critters which dislike pungent odors and tastes; in this respect, I sorround the interior border of my half acre, electrically fenced, vegetable and nightshades planting area with garlic plants, as a first defense perimeter odor barrier.

  15. Growing organic tomatoes Says:

    I agree with archangel. I use marigold, basil and daffodil as companion plant to tomato. the foliage of daffodils worked nicely.

    @Claudia: Regarding fennel, I faced the same.

  16. Katherine Gallagher Says:

    There is a great book to help with this – “Carrots Love Tomatoes: Secrets of Companion Planting for Successful Gardening” by Louise Riotte. It is filled with great info just like this!

  17. Katherine Gallagher Says:

    There is a great book to help with this – “Carrots Love Tomatoes: Secrets of Companion Planting for Successful Gardening” by Louise Riotte. It is filled with great info just like this post.

    I got it last year when planting my very first ever garden. Quite helpful!

  18. Michele Says:

    I have my tomatoes growing next to a small hedge of rosemary plants. What are the potential problems of growing tomatoes so close to rosemary. I have read several articles that do not recommend it, however, I’ve yet to read the reason why. Is it a pest problem? Fungus issue? Stunted growth?
    Thank you.

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