Why do different vendors suggest such different sowing depths?
Or better yet, what are the factors that might encourage you to sow peas (for example) deeper or more shallowly than some one else would?
I'm thinking about simple annuals and crops, not fussy perennials like:
"sow on surface" (needs light)
"barely cover"
"cover thinly"
" sow 1/6th inch deep"
For example, different seed packets or seed catalogs gave the varying sowing depths suggested below. The range for any given crop is a factor of 3 to 4!
Peas: ½" , ¾", 1" 1 ½"
Bok Choy: or ¼" to ½" deep OR ½" to ¾" deep
Lettuce: ⅛" deep, ¼" , ½"
Swiss Chard: ¼", ½", ¾"
I understand why peas are planted deeper than lettuce: lettuce e seeds & embryos are tiny and lack the resources to launch a 2" stem thick enough to push aside lots of soil. The pea root is so big it might NEED a weight of soil so it doesn't push the whole pea right to the surface.
But I see advice e to sow lettuce an where from ⅛ to ½ inch deep, and pea vendors suggest anything from ½" to 1 ½".
I'm guessing that soil type might be a factor, but this is pure guessing:
1. maybe plant shallower in heavy clay because it tends to crust and seeds can't break through
2. maybe plant deeper in dry climates & sandy soil so they don't dry out as fast
3. maybe plant shallower in cold soil because the seedling has less vigor for pushing to the surface
4. maybe plant deeper when day-night swings are large so the seedling doesn't chill at night
5. maybe plant pathogens in the soil vary widely so that some regions need to plant very shallowly to get the seedling's top out of the soil ASAP.
6 Maybe different vendors and different gardeners just have different opinions for no good reason, Yet I would think that farmers and market growers would care A LOT about what works better and then "everyone would know the answer" instead of such a huge range of advice.
7. Maybe different cultivars of the same crop have very different depth requirements and I just missed that while compiling notes.
If 1 or 2 are the reason, I would guess that anyone with a misting irrigation system could sow very shallowly because the surface layers would never be too dry or too wet.
If 4 were the reason, a floating row cover would allow much shallower sowing.
