First of all, I'm not sure this is a working spice farm. It is certainly a tourist trap though.
We were led through a small garden area with samples of various spice plants and trees. For the entire length of the tour we were told to "guess what this is" with no answer back from our guide when we gave up. It was interesting to see the various plants. But we really weren't given much information on them.
Second, someone was assigned to make us crowns, rings, and bracelets--even though we told them we didn't want them. Like someone else mentioned, so touristy. Of course, this individual required a tip.
The "Butterfly Man" climbed a coconut tree and sang from the top. Again, so touristy and again, he required a tip.
There was a fruit tasting. Very nice but once again, the person cutting the fruit (same fruit at our hotel breakfast, by the way) required a tip.
At least 2 other individuals "helped" with our tour. And, you guessed it, they needed a tip.
We made the mistake of buying spices while we were there. Big mistake. The prices were much higher than they were in the Spice Market in Stone Town.
Overall, a pretty awful waste of money.