Well, the valuable stuff tends to be broombush, jute, and glazenut (and their component seeds) which go something like this.
Linseed + Mandrake = Azeyma Rose Seed
Azeyma Rose + Mandrake = Star Anise Seed
Star Anise + Almond = Jute Seed
Jute + Mandrake = Jute Seed
Honey Lemon + Prickly Pineapple = Apricot Seed
Apricot + Honey Lemon = Royal Kukuru Bean Seed
Royal Kukuru Bean + Apricot = Glazenut Seed
Glazenut + Apricot = Glazenut Seed
Almond + Mandrake = Nymeia Lily Seed
Nymeia Lily + Almond = Broombush Seed
Broombush + Almond = Broombush Seed
Don't quote me on Broombush, I'd have to do some more digging, and there's more than one way to obtain some of the seeds listed but afaik these are working crosses (
unless the latest patch changed something regarding the final "looping" steps).
In general you'll want to use Grade 3 Thanalan soil for most plantings (though Shroud can also work for certain situations) and alternate planting your seeds in a
clockwise manner.
It appears that intercrossing (which produces the 'new' seeds during harvest) appears to only require one adjacent plant and is determined when planting - so basically don't plant something next to nothing if you want to get seeds back from it - the first one will of course be next to nothing but if it's a cheap seed you can simply tear it out and replant another once you get the rest of the beds filled.
They only need 'tended' to like once per day, you can fertilize them about once per hour which (allegedly) reduces the time to harvest by an hour with each application. Since most plants take 5-7 days to grow, a few fertilizer (which is very cheap - Fishmeal from one of the housing vendors) per day can get you to harvest about a day early.
I jumped into the second step of Jute since Azeyma seeds weren't overly expensive, but you can start wherever depending on what you want and what you want to spend initially. If you want to start some place/target something specific and any of it's unclear let me know - a lot of the information that's out there is useful and true but also pretty disorganized lol.
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I'm hoping the myth increases all around 'trickle down' to cheaper myth mats soonish
Ok, so it seems to be more of a flood than a trickle lol. There's more myth mats (50+ for some) on the AH already than I've ever seen on my server and the price is steadily trending down - I even picked up a few for less than I offer to pay through general chat. I just need more time to actually craft them now lol. I think most of the crafters seem to be eyeing new recipes and focusing on different stuff so there's a lot of room to post more 3* gear for sale.
Also when grinding out desynth I'd recommend looking for items with only one or two main materials (raptorskin merchants belt for example) - imo it makes it much more pleasant when you're guaranteed to get back a demimateria or >=50% of your material cost.