I do companion planting in what could be called "salad beds" and mostly because I'm doing so much succession and staggered planting.
Lettuce comes and goes quickly, radishes, too. Carrots may take a little longer and, while onions from sets will be about the earliest veggie, onions from seed may not be harvested until late in the growing season. Spinach is direct sown early but the lettuce is started again and again in containers and transplanted out when space becomes available. Same thing with onion sets - it isn't difficult to keep the sets in the fridge for 6 weeks and use them to follow things like radish and spinach.
Onions fit in almost too well and may be crowded by other plants to where they can't grow. They have a reputation for stunting peas & beans and I really think that's true. From my experience, I wouldn't put them together.
The classic companion planting scheme is the 3 sisters garden: corn, pole beans and squash/pumpkins. I have tried this twice: once with fairly bad results. Last season, I grew a flour corn with winter squash, pumpkins, and pole beans. The pole beans were harvested for bean soup. Everything was harvested just before 1st frost. When I tried growing sweet corn and green beans, I was stepping on the squash plants trying to harvest! The pumpkin & squash plants do a good job suppressing the weeds and don't deserve having me tromp all over them!
I still had some problems with bean vines pulling down the corn before it could develop some strength. Those 2 probably just cannot be planted on the same day! The corn plants need a couple weeks to get a start. What are called half-runner beans would probably be a better choice than some of those that grow really tall.
My garden has a fairly short season but I can set out summer squash transplants in May and as late as July 1st and expect a harvest. Of course, cabbage can go out much earlier, while there is still some chance of frost. An early variety of cabbage or, better yet, kohlrabi, is harvested even before summer heat has set in. Summer squash set in between the cabbage or kohlrabi can take off at that time and use all the available space.
Anyway, that is some of my experience with companion planting.
Thank you! That should be really helpful! I did the corn/squash/bean thing, but I had problems too...it was very hard to harvest the beans in between the rows, although, like you said, the squash did a good job keeping weeds down and keeping things moist. I can't believe its only Jan. I am so ready to start!
i've had good luck with tomatoes and zinnias. i know this one is not in my books for companion planting but i think the nice blooms on the zinnias helped to attract the nice BIG ground bees that frequent our area. a lot of good companion planting usually involves a flower growing with a veggie. it seems to help a lot with the pollination and attracting the bees. sunflowers will do nicely with cucumbers since the sunflowers can put into the soil a chemical that most other plants will not tolerate, the cucumbers can tolerate it and they enjoy the shade from the flowers. i also know that growing morning glories is a big boost to corn if they are grown together.
if you can find the books 'Carrots love Tomatoes' or 'Garlic loves Roses' those are some good books on companion planting. you can find some stuff on companion planting online but there will be a lot of different possible combinations you could use.
I can tell you from sad experience that sunflowers and potatoes will never be friends, much less companions. The chemical that chickiesmoma mentioned is an allelopath that is produced by sunflowers that is particularly antagonistic to potatoes. Corn seems to do well with the sunnies though.
I try to put my carrots in between my tomatoes (as the book says, carrots love tomatoes), can't see that I see any significant difference. I do however, plant radishes next to my cucumbers, cantaloupe and zucchini, it works very well to deter the cucumber beetle. When the radishes are ready to harvest the other plants are big enough to be on their own.
I have had good luck planting beans and corn together. However, I do have to rescue the corn sometimes. I love that my "dried" beans have something to hang on while they are drying. I did learn the hard way that I can't plant the green beans near the dried beans as the dry beans will choke them out.
I have gotten away from companion planting. I read that you will have less insect infestation if you have healthy soil/thus stronger plants. That has been my main focus and I have had better success than with companion planting. I use organic insecticides if I have an emergency but, truthfully I can not remember the last time I used any. Crop rotation is also something I adhere to. I have planted squash and pumpkins in with my corn. That's more in line with successive planting, as one matures later than the other.
I am doing companion planting this year. I also have the book "Carrots love Tomatoes". I am planning out my beds right now. Do you have some specific questions? You may want to check at your local library for the book or a similar one if you are interested in it. It is a really good resource.