The first time I grew one, I surrounded it by elderworts. (Interesting effect: as the JQ grows, the elderworts become less effective, and so the JQ's growth rate slows down. When the estimated time to maturation is updated to reflect the slower growth rate, it makes it look like the JQ actually grew younger instead of older. I almost submitted a bug report before I figured out what happened. XD)
Now I'm thinking that I should surround it with elderworts, and then add another layer of nursetulips to boost the effect of the elderworts - although there would'n't be a lot of space for this if you wanted to grow multiple JQ's simultaneously.
And of course I'm using fertilizer.
I'm guessing I could also savescum to guarantee growth at every tick, but I really don't want to have to do that every 3 minutes. I play too much CC at work as it is. XD