Plant it ASAP. If it had been indoors please either harden it off for a week or protect the new growth with an overturned pot for a few days, gradually allowing the plant to have a bit more sun each day.
pirl-OMG-I thought I was the only one that did that! Not that I'm implying I thought I was original, more like, kind of nerdy...lol. I use them for newly planted sproutes/tubers, to protect from too much sun, wind, rain, etc.
Tammy-ditto what pirl said. You could bury it a little deeper than you might normally, because of the sprouts length (makes it a little delicate?). Unless it's pretty sturdy, then scratch that. I could be wrong on burying it deeper for your zone, that's just what works here. Good luck.