The idea for the power generation plant came from the thought that alien planets could have almost any type of plants. So I figured why not have a planet where trees generate electricity that is harvested by machines? The original idea was to have the plants grow in a laboratory-like environment, but I later changed it to a forest (Fig.01).

Fig. 01
Anyway, once I had finished the basic concept in Photoshop I started to model it in 3ds Max. I quickly realized that modeling the tree in Max wouldn't be the best idea as I wanted to create quite a few variations of the main tree and wanted to keep the structure as procedural or live as possible so that it would be easier to make changes later. So I finally decided to model the entire forest procedurally in Houdini.
Modeling
Here is a rough breakdown of the modeling process for the tree in Houdini:
1. I created a central curve. The idea was to create a base curve and have the entire tree twist itself around that curve. In order to do that I started by making a line. Using a Point SOP and basic Sin and Cos functions converted it into a helix (Fig.02).

Fig. 02
2. For the vines I followed the same process except with a larger radius (Fig.03).

Fig. 03
3. I then used a Wiredeform SOP to deform both these lines around the central curve (Fig.04).

Fig. 04
4. Using a Vopsop I added some noise-based deformation on the curves.
5. To create a tapering effect I created a red gradient going from the base to the top point of the curves. Using a Polywire SOP, I used to red color to drive the width of the curves and made three copies. This got me the central trunk of the tree (Fig.05).

Fig. 05
6. For the vines I followed the same method, but kept the polywire thinner and made more copies but kept the angle randomly switching between 0-360 degrees (Fig.06).

Fig. 06