It comes down to root space competition. Large, mature tomato plants can easily have roots that fill a three-foot circle. You put other roots in there, and they will have to share nutrients. But floral_uk's point about catch cropping is a good one. If you plant fast-growing things *with shallow root systems* in between the tomatoes the competition won't be as severe, because the tomato roots will be deeper. As it happens, strawberries do have very shallow roots. All their roots will be in the top six inches of soil. Of course, something small, planted under large tomatoes, isn't going to get much sun. Strawberries really need full sun, and they won't get it down there. Common garden greens (e.g. lettuce) don't need full sun, and have shallow roots, so that might be the smartest way to go if you want to try this.

Not an expert, but it's my understanding that many of the most common herbs have pretty shallow root systems and don't actually require all that much nitrogen (or other fertilizer), but the nutrients requirement for each herb should be looked into. It's the more productive fruit or grain crops that are heavy feeders. May be worth looking into the cabbage family (like kale) that look pretty good / somewhat decorative, can be eaten and I don't think are heavy feeders either (at least friends that have grown have said they are pretty forgiving, don't know about growing alongside tomato).

I would agree that planting basil in between the tomatoes will pose no threat at all. If this is an inground planting (which I believe it to be), the basil will require no additional fertilization above what is already being provided for the tomatoes.

The strawberries will work perfectly well also but may not receive enough sunlight to be very productive. Expect most of their productivity to be earlier in the season before the toms really get going.

The only problem with basil is that the plant can get quite large. Lettuce is a good choice for intercropping - also radishes.

Actually, I like the idea of basil. It can get large, but most tomatoes will eventually dwarf it, especially when they start to produce. Smaller plants won't just suffer lack of sunlight. They'll be completely lost underneath the tomato foliage. You can pick your lettuce - if you can find it. Vertical brassicas like collards or kale will also stay in sight.

On second thought, cancel that about brassicas. They have very deep roots, and will compete with the tomatoes up the kazoo. Basil roots will stay largely in the top 8 inches.

I wouldn't put tomatoes and strawberries together, even if the strawberries are in containers. I planted a tomato in a strawberry bed, this year. It turns out, some of my strawberries had a disease, and the tomato caught whatever it was. I didn't get much fruit from the plant, either, compared to another tomato of the same variety (Tidy Rose F1) planted with tomatoes (granted the other one had black plastic and this one with the strawberries had shredded wood mulch).

My wonderberries didn't catch the strawberry disease (I have two plants in the patch). My uninfected strawberries probably all caught it. Maybe I'll make that a wonderberry patch next year.

Basil and tomatoes are said to go well planted together. I don't see a problem with that, other than that some tomato varieties might smother it after a while. I've never had a need to fertilize basil in the ground. It's pretty low-stress for me (just prune it when it starts to go to seed if you want it to keep producing leaves). Has anyone here ever had basil in the ground with chlorosis? I haven't: I'm just curious how much need for fertilizer others have. I wouldn't say my unfertilized basil plants get large (but they produce more than I need). They get maybe two feet tall at the most.

What tomato varieties are you dealing with?

Thanks for the tips everyone.

As far as the sun issue, i will see but I think it should be ok because im going to help him trim and trellis the larger plants in a way where there will be plenty of sun getting underneath. He has a rail behind the planter and a few other areas where the stems and vines can be really elevated.

Dan, why would a faster growing plant be better in this case?

I used to try to efficiently plant things next to each other in accordance to their root depths but then I was made aware that even deeper rooted plants have surface roots. Can someone tell me, do deep and surface roots both fulfill different, unique roles? So if I have many strawberry plants right next to a deeper rooting tomato, will the tomato compensate and throw out more deeper roots in areas below hat aren’t colonized by the shallower strawberry roots?

Dan, I think I remember you saying that a shallow rooted plant next to a deep rooted one will block fertilizer and water from the deeper rooted one. Following up on that, what if you made sure to give extra water and nutrients? I know water really isn’t an issue here for my friend or even myself. We both save all of our greywater water and always have extra. Expecially for him, since he is in an apartment he goes through a lot of water but doesn’t have nearly enough land or plants for him to use it on.

I thought radishes might be a good idea but wouldnt tearing them out of the ground routinely be bad for the tomatoes? I would think with strawberries or a perennial, you wont have to disturb the soil every time you harvest

Shule, I too have heard about the disease issue namely verticillium wilt and that was definitely a concern. I will research more about it because I found a few topics online about the very same thing. . I will check on what tomato varieties hes planting too

I don't think I ever said that a shallow-rooted plant will block fertilizer to deeper rooted plants. The fertilizer is carried by the water, and the water just drips right through the root layer. But there will be nutrient competition. The liquid that drips through to the roots down below will have somewhat less nutrients than what was applied at the top. If roots are going to share soil area, there is just going to be competition. No getting around that.

I really can't imagine how you'd trim a tomato plant to allow sunlight to hit the soil effectively. You put the plants on a trellis, and they're going to block all the light coming from that side. Trellisses cast a lot of shade. Tomatoes need sun, and the sun that is hitting the tomatoes isn't hitting anything else.

Radishes would do, and they're only an inch or two deep, so the tomato roots would never be aware of a radish being pulled out above their roots. Good idea.

Bottom line. If you have plants sharing the same soil area, they may do OK, but they won't grow optimally. That's because of nutrient and sunlight competition. So if you accept that, then go for it.

I think it's too simplistic to say that there is inevitably competition for nutrients and rootspace and sunshine although it depends what you mean by growing optimally (and @daninthedirt did admit that may be acceptable). Now sure, if you're trying to grow some prize-winning tomatoes and nothing but those tomatoes, maybe the competition is harmful. And obviously two very heavy and dominant plants with high nutrient needs may compete to the (significant) detriment of both - but some combinations may work very well.

It's not simple at all, it's not just competition - some plants need more or less sunlight, and partial shade from 'competing' plants may hardly affect some or even be beneficial. Some soil cover from other plants grown alongside might be beneficial. Plants don't generally use all of the nutrients in the soil, certainly not all at once, and they may have different needs at different parts of their growing cycle. The nutrient requirements are often described in terms where you look at which nutrient is the limiting factor (often nitrogen) - and for many of the nutrients and especially micronutrients, once they have 'enough' of that particularly input, adding more doesn't make any difference (and competition from other plants is not a factor); some plants bring their own nitrogen by fixing it at the roots. Likewise with root systems - root systems of different plants coexist all the time, and may even be beneficial to each other - helping soil nutrient exchange, drainage, tilth of the soil, etc. (Yes, of course, some root systems will outright compete with each other - you don't want to try to grow tomatoes in the dense woody root system of a big tree). Other things - microorganisms and fungi - are also present in healthy soil, and they're not all 'competing.'

Now I'm not trying to push anything - just saying that 'competing for resources' is not necessarily the right way to look at it. It depends. In fact the limiting factor concept may apply well to most of the inputs - sun, nutrients, water - although water is probably the easiest to grasp, ie. once the plant has enough water it won't be affected by other plants taking more.

I'm not a chemist but I think the way to look at nutrients in soil is not as if you're feeding a dog with a bowl of food (and the cat eating the dog's food is direct competition), but as a chemical solution - ie. as a percentage of the whole (the concentration), the total physical amount is not so much the issue because plants absorb nutrients differently.

Some plant may grow best when (say) potassium availability is above X% (and below some other percentage); the difference to this way of looking at it is that the plant doesn't necessarily 'consume' all that much of the total potassium in its area, it absorbs enough and grows best by chemical exchange when the potassium concentration is in its optimal range (the plant's processes to absorb chemicals work best in that range of concentration, regardless of how much it actually physically needs in weight or volume terms). As long as the other plants don't outright consume so much that they throw off the concentration, it's not really a limiting factor. Note, I'm using potassium here a bit randomly - nitrogen is I think a bit more complicated, both because some plants require a fair bit and that nitrogen is more volatile and not as persistent in the soil.

This is obviously a simplification as there are concepts like availability, the nutrients aren't in a liquid solution (soil is quite complex and heterogenic) even if overall it acts like a solution, may be partially/loosely bound to other chemicals, tied up by microbes, water is the most common solvent so moisture affects all of the above, aeration of soil matters too, etc., etc.

' I would think with strawberries or a perennial, you wont have to disturb the soil every time you harvest'.

But you would disturb the perennials every time you plant or pull up the tomato plants. Catch cropping wth a fast growing crop like lettuce seems a much better bet to me than trying to establish a strawberry bed, which would be in place several years, in an area which is going to be prepped and cleared every year for tomatoes. You can cut lettuce and leave the roots in situ so there's no disturbance. And pulling a radish is no more disturbing to the tomatoes than pulling a weed.

Some people say basil and tomatoes are companion plants, and that growing them together makes the tomatoes taste better. I don't know if that's true or not, but yeah, I don't think it'll be a catastrophe planting them together either way.

It's nonsense on the taste front. But it's handy to have the two complementary cooking ingredients side by side for harvesting.

That's a fair point that "competition" is a simplistic way of considering plants being planted together. But in a general sense, that simplistic assessment is correct. No one is saying that one plant planted with another will kill the other plant, but they aren't obviously going to help each other. The best way of looking at it is that if you don't know the details of your soil chemistry and the particular needs of a given plant, planting things on top of each other just isn't that smart.

But again, we're talking optimal performance. If you say "I just want some tomatoes and strawberries", instead of "I want the most and the best tomatoes and strawberries that will win me prizes", then you're good to go.

Agreed about companion planting not improving taste. Myths abound. But yes, if I'm cooking with tomatoes, having fresh basil around is pretty nice. Good point about pulling radishes being like pulling weeds.

It's a pretty common practice to grow quick greens or flowers between large plants like tomatoes and squash. Marigolds are traditional for this, though I'm not sure I believe that they repel important pests of tomatoes, but it's nice anyway. Arugula grows quickly and you cut it right down and eat it before the tomato plant spreads out to shade it. Basil is traditional too but likes the same temperatures as tomatoes so I find it doesn't start thriving and getting big until the tomatoes are shading it. Any other quick greens are preferable in my experience: arugula, lettuce, any other quick greens like mizuna, bok choi, edible chrysanthemum, maybe spinach, really any quick greens; kale is too big and long-season, and deserves a spot for itself. I try to keep these catch crops at least 6 inches away from the base of the tomato plant.