Plants no longer sparckle when they are ready to evolve you just need to hover over them and check out their level scale. When they have reached the max for their current level they are ready to evolve. Plants also seem to take longer to evolve the higher up they get and the rarer they are.
They only produce havestables at 5am so if you aren't on the lot/zone at 5am they won't have any havestables. You also need to be in the zone long enough for the plants to grow as it seems once you leave the zone they reset and have to grow all over again.
Splicing plants for rarer plants is also hard. I have two spliced plants to get birds of paradise and have yet to get them and it has been over 3 maybe 4 weeks. Apparently they do spawn but the have a low chances.
Edit: I don't think gardening is wonky I think it was made easier in aspects but harder in others. I would change it so that plants could produce havestables at 5am and 5pm but overall plants would be given a 24hr time limit on when they can be harvested again. That way players would have a chance during the day to get harvestable from plants out in the world but still only be able to harvest once a day.