ah good ol rustica. there are some varieties that have been bred that will stand up more like a tobacco plant and have larger leaves, but most of them bush out and have small leaves. if you're growing the same variety as you did the year before and didn't see any early suckering last year, my money is that they're probably stressed in some manner. many rusticas will quickly move to flowering (rapidly followed by suckering) if they are stressed by being root bound or have root damage (pathogens, nematodes, maybe water logging, etc).