the spawnchunks are unloaded just like the normal cunks

I was building a sugar cane farm in my spawnchunks, then I go to my house that's one thousand blocks of my spawn chunks, after ten minutes I was back, and my sugar canes has not grown.  I did a test in another world with the same seed in the same place, I put the ticks of the game in 1000 and I teleported far away, I waited twenty seconds and i was back when the sugar cane arrived, nothing had grown.