Stem

Select Edit | Deselect All to make sure nothing is active on the stage.

In the timeline, click the New Layer icon to create a new layer. Double-click the layer and change its name to stem. Drag the layer so that it's between the flowerpot-front and flowerpot-back layers. This will allow the flower stem to appear to be growing inside the flowerpot.

Click the Brush tool and select the third-largest brush size from the brush options. Leave the brush shape at its default (round).

In the Property Inspector, change the color displayed in the fill property box to green.

Highlight the stem layer and frame 1 of its timeline.

Paint a small circle inside the flowerpot.

Referring to the timeline, the stem should appear to grow for the first third of the movie, about 10 frames. So, the fully-grown stem should be in place in frame 10.

Select frame 10 in the stem layer and choose Insert | Keyframe from the menu.

With frame 10 of the stem layer still highlighted, click on the Brush tool and draw the fully grown stem. Note: the stem should reach no higher than 250 pixels from the top of the stage, to allow room for the flower graphics.

To make the stem appear to grow, we can add a tween between frame 1 and frame 10. In the stem layer, highlight frame 1. In the Property Inspector, select Shape from the Tween drop-down menu. Press the Enter key or select Control | Test Movie to play the tween.

The result should look like this:

And play like this: