Plant shadows can be individual to each plant, or can be connected to the document…
Vectorworks Tip #247 – Plants – Default Plant Classes
Many of the plant objects that come standard with Vectorworks have a class structure already. You could call this the default class structure for plants. Generally the outline of the plant is on a specific class (Plants-Component-Outline) the color fill is on a specific class (Plants-Component-Color Fill) and the line work is on a specific class (Plants-Component-Interior Linework). Having parts of the plant on different classes allows you to choose which parts you want to be visible in the various viewports.