JB

That's a good question, and the answer is that there's something in the brassica family that stunts tomato growth. From the link below.

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Broccoli, Brussels sprouts, cabbage and cauliflower all retard tomato growth, and share some pests in common.
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There are several plants that negatively affect the growth of other specific plants. It's called allelopathy. Here's more information about this phenomenon:

http://edis.ifas.ufl.edu/HS186

I don't think onions would work as a barrier crop, since the chemical reaction occurs and spreads in the soil. Maybe your solution is to grow one or the other in containers.

Here is a link that might be useful: Companion plants for tomatoes

I grow broccoli, cauliflower and cabbage with in three feet of tomatoes with no problems. Of course the brassicas are harvested before the tomatoes start producing.

I have never heard of broccoli affecting tomatos.

There is such a thing as allelopathy, but the black walnuts will have way more of an effect on the garden plants than any veggies planted near each other. In your case the garden being 30ft from a BW should be fine.

Plant and enjoy.

Same here - grow them in the same beds and in the same rows and have for years with no problems. Have even followed up broc with tomatoes in the exact same place once the broc is harvested.

With no offense to Anney, many times all the "companion planting rules" just don't hold up in real experience, and since your space is limited about all you can do is give it a try.

Good luck with your new garden. ;)

Dave

Ah, Justine. TWO experienced gardeners say they can be grown together, so the advice I've been following is questionable!

I generally do try to find research about questions rather than relying on gardening sites that make recommendations, but it appears that the research on the effect of broccoli/tomato together hasn't been direct. Instead, I've seen a couple of sites where researchers say that the addition of chemical components in brassicas has a growth-stunting effect on tomatoes. But if it actually does, it must not be appreciable since people say they grow them together and they're fine.

So I agree that all you can do is give it a try.

Can't count!

THREE experienced gardeners...

My experience has been that most companion planting is not for me. I won't hold it against another if they practice it, but not in my gardens. However, I have used onions as a barrier for various rodents, to deter them from scurrying out of the fields directly into the other root crops.

Anyway, there is one very good reason to keep most brassicas away from tomatoes... And that is because brassicas as a group are heavy feeders. It might be easier to prepare the soil for brassicas if they are kept to their own patch. Otherwise, you might end up with too much nitrogen in your 'mater patch.

I'm pretty new too, but I'd take any of the companion planting stuff with a grain of salt, unless it's been shown in a well-controlled study. (Of course if my cauliflower kills my tomatoes, I'll eat my words)