Model the Base

Draw an 8 segment circle with a radius of 150mm.

PushPull to a height of 250mm.

Select top edges and move a copy using CTRL + Move constrained downward 200mm.

Type /4 or 4/ into the VCB to perform an array.

Select every 2nd loop and use the Scale tool to perform a uniform scale about centre by 1.2(holding CTRL will invoke 'Uniform about Centre' mode).

Offset the top face by 50mm.

Offset the bottom face by 50mm.

Select the top and bottom faces and move downwards 50mm.

If you have the Vertex Tools plugin select alternate vertices on the top and bottom loops. Move them upward 55mm. If you don't have Vertex Tools them you can move each point individually using the Move tool.

Scale all 4 vertices by 1.1 holding Shift and dragging on the handle indicated(alternatively you can select the loops and perform the scaling).

Select the opposite vertices in the middle loop and move these upwards 80mm.

Select all (CTRL + A) and group it either via the context-menu or the Edit menu. The Entity Info box indicates that it is a Solid Volume, meaning it has no holes or contains no internal geometry. You will need this solid for the next step

Construct the trunk

Move a copy upward 290mm using CTRL + Move.

With the Move tool still active rotate the top group 45 degrees.

Select both groups and move copies upwards 580mm.

Type 14* or *14 in the VCB so you array another 13 copies upwards.

Select all and use Outer Shell to combine all groups into one solid group.

To taper the trunk use FredoScale's Taper tool and perform a 'Uniform about Centre' tapering (tap CTRL to invoke 'about centre'). Enter 0.65 and the taper value.

Finally use FredoScales Bending tool to deform the trunk.

Alternatively use Vertex Tools with a Cosine Falloff and manipulate it to your liking.

The final result should look something like this.