[KeroKero]

I'm not sure they'd "rather" be growing emersed, as much as emersed growth is part of their life history - they don't want to be either way completely. Now if you're talking about the plants in a tube at Petco you're more right because at least half the plants they grow are TERRESTRIALS. Bugs me every time I see Selaginella and Dracaena stuck in those tubes just because they don't die right away... but the good news is I haven't seen a plant in those tubes that isn't a good viv plant

Cryptocoryne natural history ranges from some species that never get fully emersed (but live with wet feet) to those that live their life almost completely submerged and don't always do well emersed. You can't really go wrong with trying any of the crypts that are mass propagated that you'd find at the pet store - they tend to be the hardiest and adapted to the widest range of conditions and aren't one of the specialty species (like the blackwater species I keep). Most of those plants were actually propagated and grown emersed, and not submerged until they got to the pet store.

One big thing I think that hasn't been mentioned is that crypts are heavy root feeders - they are going to want to be able to get some food from their roots. I do this by using mineralized top soil and/or aquasoil that they can dig their roots into. Doesn't have to be much, but until you have some good detritus building up you're not helping their cause.

The best way I've found to start crypts in a tank for emersed growth with as little leaf lost as possible (a lot of the crypt melt is related to all the disturbance - in the wild all this disturbance means water level is raising or lower so it's time to drop the current leaf set and grow a new one!) is to just toss the plants on top of the substrate you want them to grow into with the water level a bit higher so the plant stays wet. If you just let it lay there you won't rot or damage the crown at all, and pretty quick the plant with right itself, send down roots, and you'd never know! I usually cut off a lot of the root ball when I do this.

The thicker the leaves of the plant, the larger the loss of humidity it can take. Some Crypts are sturdier than others... I've been playing with C. lingua (which will die submerged) and it's a pretty tough cookie even with a seasonal dry out (as long as the roots stay wet) and is keeping up with anubias in that sense. Most of the others would have cried mercy already

 

[KeroKero]

But then you have to ask the question, was it because he didn't grow ones that always liked to be submerged? LOL.

I think a lot of the crypts that spend a majority of their life submerged (long strappy leaves so they can flow with the current easily) may be touchier about transitioning than some of the others. They may not take sudden change well are are more likely to melt completely than just melt leaves (enough people kill them then they "can't be grown emersed!"). These also tend to be the species that don't take transition well like replanting. A number of these tend to also have (comparatively) very long spathes that they send up above the water level when it's low, adapting to the fact that they don't dry out enough to send up a short little spiral like their relatives. There are a couple of specialty species in the hobby that fit this description and tend to have a high death rate for some of those reasons - but I've seen the same species grown emersed. The recommendation seemed to be to have the water still above the substrate level if you can. Once established though they seemed downright hardy.

At least one fern has found a way to get around the submerged issue of reproduction... Java ferns are well known for producing plantlets along their leaves while submerged (and are more than happy to do it emersed when their leaves touch something with moisture), and the plantlets easily break off when good sized with roots to float downstream and wedge somewhere. Some forms of this species (including or not including the synonym M. brassii) have never been found emersed at all. At least one form in the fish hobby WILL NOT grow emersed, even after two years of trying every trick in the book that I (and some excellent crypt and fern growers) know. Not a huge loss to the hobby since there is a similar form more than happy to grow emersed, but an oddity to be sure.