I’ve also run across some discussion and experiments when it comes to planting tomato plants “deep”, shallow, or in a shallow trench. Most advice is “deep”, but some experiments show a larger root system develops when the young plant is turned sideways and placed in a shallow “trench”, then turned upwards at the leafy end. I can see this working best with “spindly” starts.
Interestingly, production varied very little between the 3 methods if plants were kept well watered but not over watered, in a good soil (etc.) environment. Commenters replied that deep planting was needed if watering was sporadic in dry summer climates. OTOH, others pointed out that water “pooling” above a layer of dense clay could cause weak and diseased roots, making deep planting problematic. (I believe I have some trouble with this, sometimes.) There is also the problem of turning the plant “upward” at the end of horizontal trench.
Cutworms can also be a problem with deep starts of young tomato plants, as the base of the plant is usually tougher than the tender upper half - which stems I’ve found cutworms and snails to love...
What about a 4th option? Dig a short (12” long?) trench that runs from shallow to, say, 10” deep? (Trench length & depth can depend on how tall and spindly the young plant is.) This helps quite a bit with bending the plant “upright” as it exits the ground. It also works out well for “spindly” starts. It doesn’t help with cutworms and snails, however...
A final benefit is that if one has semi-permanent support for their tomato plants, on can rotate the location of the root ball around each support, from year to year. (Probably one should avoid placing the root ball under pathways!)
Thoughts?
I planted a few tomatoes yesterday with this slanted trench approach. We’ll see how it goes...
I plant my tomatoes deep - up to the first set of leaves. They are usually 8 weeks or so old when they go into the ground and of May. Every tiny ‘hair’ on the stem has the potential to become a root.
I put 1/2 cup crushed eggshells and 1/2 cup bone meal in each planting hole. Water in, throw the large square cage over them, re-adjust the straw mulch and get on with my life. ;)
When we grew for market, my FIL trenched his tomatoes - same reason - you want lots of root development for strong, productive plants. His variety of choice was ‘Celebrity.’ That’s all he grew and we always had TONS of tomatoes to sell at Sunday Farmers Market and to a few local restaurants. It doesn’t crack, good shelf-life and was bred at the UW Madison, so both everyday Customers and Chefs liked the local nature of that tomato. (I still grow it.)