Bury the stem

[Hillbilly69]

You can bury the stem up to where the cotyledons were (first small round "leaves") with no issues, I've done it many times. As long as you're using a well aerated soil, it will just throw out more roots. Feeder roots will also grow upwards. Even putting a layer of hydro clay pebbles on the top of your soil will allow roots to take full advantage of soil. I use them a lot and the top of the soil under the pebbles is always a root mat.

 

[Ringodoggie]

Even putting a layer of hydro clay pebbles on the top of your soil will allow roots to take full advantage of soil. I use them a lot and the top of the soil under the pebbles is always a root mat.

I must admit, that's a new one on me. I don't believe I have ever seen anyone post a picture of a plant with a root mat on the top. I may have to try this.

 

[Hillbilly69]

I must admit, that's a new one on me. I don't believe I have ever seen anyone post a picture of a plant with a root mat on the top. I may have to try this.

Lol! Root mat meaning tons of roots, not quite like you'd get at the bottom of the pots. Keeps top of soil moist and no light, so roots grow thick on surface. Try it, maximizes usable root zone

 

[Hillbilly69]

I also use root enhancers, so I'm sure that helps. Big root systems = big yeilds.

 

[Cerathule]

You can bury the stem up to where the cotyledons were (first small round "leaves") with no issues, I've done it many times. As long as you're using a well aerated soil, it will just throw out more roots. Feeder roots will also grow upwards. Even putting a layer of hydro clay pebbles on the top of your soil will allow roots to take full advantage of soil. I use them a lot and the top of the soil under the pebbles is always a root mat.

Yeah, me too. It also helps with handwatering and keeps the room cleaner. The water gets better distributed and no dry soil particles sprinkle away. The only downside is you can't see the level of dryback the potting mix has.

edit:

^Buttress roots of maize.
They serve mostly to stabilize the shoots axis, but can also uptake water and nutrients, though not as much as normal roots.
There are trees that have something similar - stilt roots.

These are some real air roots, the plant develops them as part of its normal habitus. Now, it's also possible for white roots - which actually should be underground - to become green and woody when they face light and dryness. For example, when growers fail to bury the rootball adequately upon repot, then the fresh soil around it sinks lower with watering, and the roots close to the plants base get exposed. But these are not genuine air-roots. And once unearthed they may not develop so many topsoil side roots which grow below the surface where, outside, they usually find the highest levels of humics and other substances released by the decomposition of fresh organic material.

^this is an illustration of C. sativa roots system in outdoor soil.

Indoors the root ball will develop way differently, but it's largely dependant on pots used.
With airpots or fabrics the roots will develop everyhere equally.
With plastic pots there will be way more roots at the bottom of the pot, and the upper region there will be less. Especially when one plants the seedling directly into the final (closed) pot. Which is something that seems to be broadly established for Automatics, advised by breeders. There was some speculation about this why, and arguments raised ("when the tip of the roots hits the bottom of the pot it will start to flower" seemed to have been taken from Darwin's 'root-brain hypothesis'). Personally I'd rather use a smaller container and uppot 2 times, just before the plant gets an inkling to be rootbound.
There's some evidence there rootbound plants don't develop as branchy as usual so this could even be a method for crop steering.

One thing I'd do with plastic pots starting from late veg, or bloom, is a "minor watering" after about half the time in between full waterings, by just spraying the topsoil when it has dried out, to keep the roots there alive, and make new roots grow there. Since I'm using organic soil this part will also release nutrients and esp. the bacterial life needs water as well. But I wouldn't recommend this to anyone not firm on water practices as esp. new growers usually overwater and that creates way more problems than some unused topsoil.
It's also that not always all plants drink the same amount, so I use this intermediate watering to leverage the soil saturation in such a way that then in another 2-3 days all pots will be equally ready to receive a full watering (until drain).