Tentacle Tree won't grow

@ArchAngel1294  Well, it looks like you have the Seasons Expansion Pack. 

You have to visit Sixam in the right season to get the alien plants.  The Tenacle tree produces Fang Flowers in the Spring.  The Quill Fruit is in the Summer and the Glow Orbs are in the Winter.  So you weren't there in the right season.  

Since you only visit Sixam for short periods of time and, without cheats, sims can't stay all that long, you will have to go several days in a row and stay as long as you can to let the plants grow.  Once the plants grow all the way up, then you have to be there when they bear.  They won't bear fruit if you are not there and are just like every other plant in the game which begin bearing fruilt at 5 AM.  So you have to get there before 5 AM and just wait to 5:30 to harvest, you will get the full daily amount the plants bear..

If you get there are the plants are still full size, then you can also take a cutting and graft it to another plant later.  For some reason, when you take a cutting off one of the Sixam plants, the plants will die.  But they do grow back.

Hope this helps.