We plant our Kohlrabi within 1 foot of our tomatoes not an issue. In fact the tomatoes are doing so good that we are getting ready to can them. ........N. Arizona

I don't normally plant anything within 3 foot of a tomato plant simply because tomato plants need that much room or more just for itself.

I sincerely doubt any "stunting" issues and I have planted kohlrabi in adjacent rows to tomato plants with no problems. But since they have such different nutritional and water needs I wouldn't want them any closer.

Dave

I think there is some research that suggests that brassicas are mildly allelopathic when water extracts of the plants are applied to other plants. For that matter, brassicas also produce hormones that are growth promoters for other plants. That all being said, I've never seen any issue with them just growing near other plants.

Agree with farmerdill. These two crops aren't typically planted at the same time. In my area kohlrabi can be planted a good month or more before tomatoes. Which means the kohlrabi should be almost mature, if they haven't already been harvested, by the time tomato plants start becoming large.

Rodney