I have found that planting tomatoes deep is undesirable because it puts the roots in contact with cooler soil. When I am planting out tomatoes in May, the soil is warm at the surface, but gets cool very quickly as you dig deeper. So planting deep is counterproductive for me.
As far as nutrients go, there are more nutrients near the surface than down deep. This is particularly true in a no-till system where compost is applied on the surface.
I sometimes plant my tomatoes laying down, so that they are fully in contact with the warmest possible soil. The tops get bent just a bit to emerge from the soil upright, and they then grow vertically just fine. This works well if I have grown out large plants in large pots, where to plant them vertically would put them almost a foot deep. Hope this makes sense, the key is that transplant pots are deeper than they are wide. So I flip them on their side when I transplant them out to the garden.
Wendy, I tried that one year. I can't say if the plants did better, fruited earlier, or if the tomatoes were better because I didn't plant a normal row next to them in order to compare. Back in those days I wasn't experimenting yet. But anyway, the plants did fine and I got lots of tomatoes, as usual for back then.
But I noticed something very important in the fall when I ripped the plants out. The roots looked like any other normally planted tomato. All the deep section that I gone into the effort of planting really deep had disappeared. By looking at the roots, you would never have guessed it had been deep planted.
So deep planting might help get a plant established especially if it is spindly or if things are dry. But somewhere along the line the plant appears to reject that deep section of roots.
Now when I have a tall seedling I simply plant it on its side. It's a lot easier than trying to dig a deep enough hole.
It's never too late to start! I retired to homestead on the slopes of Mauna Loa, an active volcano. I relate snippets of my endeavor on my blog : www.kaufarmer.blogspot.com
Location: Currently in Lake Stevens, WA. Home in Spokane
posted 5 years ago
And, the other side of the coin:
I have had good luck planting tomatoes deep. I have used the deep method in both coastal SoCal, and Puget Sound areas.
I transplant to the point that the first (true) leaf is just above the surface.
The entire buried stem will begin sprouting roots. These 'extra' roots become mostly lateral, surface roots, while the original root system goes deep. This gives the plant a deeper root system, as well as better surface roots. This has seemed to make them better scavengers for scarce water.
I guess 'it depends' on your circumstances. If your subsoil is too cool, perhaps it will slow early growth.
If water is a problem, perhaps the better root structure would make up for it.
Next season, I hope to be in an area with a shorter season (but warmer summer). Perhaps I should try both and see which way works best in the new region.
A larger root system generally means a healthier plant, but I am not so certain that this is so important in an annual plant. With a perennial, you really want the plant to spend its first year developing strong roots. When the goal is annual fruits, you want the plant to quickly get into the 'reproductive' cycle, rather than devoting too much time to make itself 'permanent'.
R I've had great success doing this with leggy starts bought at the farmers market in late June. Plant em up to their necks and they end up producing well before the season is through. I do tend to do it on a diagonal instead of straight down.
I've done this a bunch of times and have gotten good results. As Terri points out above, you can lay them on their side while you harden them off, which will cause the plant to develop a nice bend in them making it easier to bury their stem just a few inches deep along the surface. In my opinion, the advantage here is gained by increasing the amount of surface feeder roots that the plant creates. When I've simply planted them deeper, I haven't noticed an overall deeper root system when I pull them out in the fall. I think that deeper stem simply dies back.
So very odd that today I pulled some late-planted 'maters, and took a good look at the deep-planted roots. The main root was amazingly thick for the entire length it was underground. I see in the thread above that someone plants them on a diagona;, and others shallow. I guess a person would have to plant some of each and keep track of what is where, and of course, how they do.....
I have also read that tomatoes like a hot root zone, and not to mulch them until they've set fruit and the fruit is as big as 2" across... IDK..... Our tomatoes go into shade about 4:30 in the afternoon, and in hot summer weather, I think that helps them.
Varying results may have to do with soil type. Tomatoes will root deeply in search of water in warm sandy soil that has to much drainage. On moist, heavy clay soil in cooler climates, the roots stay near the surface where temperature and drainage are favorable.