You could probably move them if they have only been in the garden a few weeks..You'd have to make sure you took a big rootball and moved them carefully...You didn't say what kind of plants you have and that could have a bearing on the spacing..

I'm a first-timer, too, but having probably read some of the same books, I can tell you what I did. My tomatoes are also planted only about 18 inches apart, but I think this is fine if you have them staked in such a way as to encourage tall, narrow growth. I'm using Tomato Towers, link posted below, and you actually pinch off the runners to encourage tall, narrow growth. This way, the plants can remain fairly close together. And, from what I've read and heard, this should also help encourage plenty of blossoms and fruit.

I think I'd be inclined to stake your plants with the towers rather than try to dig them up and transplant them at this point. Best wishes!

Here is a link that might be useful: Tomato Towers

Thanks for the responses, still undecided.

They are still very young (we've had cold weather up until recently), so none of them are taller than 6 inches out of the ground (I buried them deep when transplanting).

And I'd agree if they were all 18 inches, I might try and sneak by, but I planted some as close as 12 inches, which I think is way to close.

Any more opinions would be appreciated!

Square foot gardening has you plant them 12" apart, then train them to stakes and prune off all the suckers. As I understand it, they will grow acceptably well in this manner, with fewer fruit, but you can shoehorn more in so theoretically you'll have more plants, and thus more production over all.
If you have plants that are indeterminate, I'd leave them, stake them and prune the suckers because the vines will continue to grow vertically and fruit on new growth. If they are determinants (aka bush varieties) they are programmed to grow to a certain height and set most of their fruit at once*. Because of their growth habit they produce better for me if they're caged and left alone, so I'd try to move them.

* some are semi-determinant, which means they will stay small and may produce a few more fruit as the season progresses after their initial rush.

Thanks - I should have clarified they are indeterminates (Better Boy and Sweet 100's).

I'm still leaning towards trying to move two of the plants, as they are still so young.

Also I figure if I can thin out two of them, even if they don't survive the remaining 4 planets will probably produce much more heavily with the extra room, so it might be a wash.

But feel free to correct me if I am wrong!

That could be a good idea. If you have them placed like a six pack ::: take out the middle two and pop them in further down.
If you need any help let me know, I'll send my dog on over just as soon as she's finished digging up the holly bushes. :/

They aren't placed exactly Like a 6 pack.

They are like this:

X X X X X

X

With basil and peppers filling in some of the others. I think I'll try to move the second one in from the left, and the second one in from the right to look more like this:

X -- X -- X

X -- X -- X

Even thought I might end up with some shade issues, I still think I'll be better off.

Can't decide!

I would definitely move the Sweet 100's. The plants get big and consume a lot of space. Considering, the cool weather we've had, the plants have been stalled in their growth. I don't think it would delay them any further to move the plants (but do it soon.) As soon as the day temps are regularly in the 70's and night temps are in the 50's those plants are going to want to grow.

Thanks boo :)

Looks like you are in the same zone as me, so that's good to hear advice from someone who has had the same temperature issues so far.

I'll try and move them tonight.

I AM SOOOO DISAPPOINTED!

I thought you meant your tomatoes were moving around the garden, like on their own.....

Sue

lol now sue i have seen some strange things but trust me on this if i see my tomatoes doing that i swear i will be using some weed-b-gone.

LOL Sue!

Anyway, I moved the planets, they came up VERY easily as when i started the garden (due to my bad clay soil) I had several yards of top soil / compost delivered for my first year so the soil is real loose.

Here's hoping I didn't kill them in the process!

I've moved plants around a bit this year. Twice actually due to my ignorance of where and how to plant things ;) They seem to have moved just fine! Nothing had major roots and I was able to just use my hand and dig down and scoop over under them until I felt it come loose and then transplant with a bunch of dirt still stuck to the roots.

Fingers crossed that all is well!

I moved a 2 1/2 foot tall tomato plant bent completely over by a hurricane. I dug it up and planted it way deeper , passed the bend in another spot in the garden. It did fantastic--no problems at all.

I think it is good that you moved them--I don't really like to prune and I haven't had great success when the tomatoes are way too close.