Joshua, I haven't tried core gardening, but I don't see any reason it would rot roots. I also don't see any reason some plants would be less satisfactory for the approach, as long as you have decent soil. Mels mix works, but I personally like the compost part of it and don't love the other parts. Plants are happy in it though. If you're new to gardening, then ignore everything I say and just get started with it. Plants want to grow, and are remarkably forgiving as long as they have decent soil. Nothing substitutes for
experience, so jump right in, try things, kill a few plants, eat a few more. It's all learning.
If you're still reading, here's a few other things your question brings to mind...
If the reason you're trying this is concern about plants drying out, there are at least three other things I'd consider as options alongside this... ordered from least to most preferable to me:
Drip irrigation. A simple timer and a few parts let you put water when and where you want it. I'd rather not fund the plastic producers, but I have used drip irrigation before, especially when establishing plants during the heat of summer when I'll be away too often to care for them well.Straw bale gardening. If you have straw to put in that trench anyway, why not consider straw bale gardening and save the effort of making the bed and mixing the soil?Hugelkultur. The core idea seems to me to operate with the same intent as hugelkultur, just a bit more urbanized.
If you're not familiar with straw bale gardens, check here:
https://strawbalegardens.com/. His TED talk linked from that page is 15 minutes well spent. If you try straw bale gardening, please do know that you can use any nitrogen source to condition the bales. There's no reason you must use a chemical fertilizer for that purpose.
If you're not familiar with hugelkultur, a search on this site will find you tons of info.
None of this is intended to talk you out of core gardening, simply related ideas you may find helpful.
If you try it, let us know how it goes.
