Hi Leif. I’ve bought the Haxnicks deep rootrainers and find them great for seed such as beans and peas. Easy to fill and I’ve had no trouble extracting plants once ready to go out. Should last many years too. Not sure I’d bother with carrots and parsnips in them but, if you have mollusc issues like Hawfinch, I wouldn’t rule the idea out.
Nearly time to step up to the start line here in N.Yorks 🙂