When I do my weekly 50% WC in the 220g all the 30" tall background plants bend over. As long as they stay wet and aren't actually out of the water. After I fill the tank I just take my 24" long tweezers and gently get everyone standing up at least in some order. By the next day they are fine. Only stiff plants like Bolbitus or anubia's can be problems since they won't bend. So the wisteria will be fine. One thing you can do is if you want a bushier grouping then cut it and replant top/s next to the original plant and it can grow and form a thick bush. It's really up to you if you want it tall now or if you want it tall and bushy by cutting and replanting. In my tanks I tend to cut and plant until I get the amount of plants I want for thickness of groups and then let them grow tall together.