The size of a plant is determined by properties in the Plant Encyclopedia. You can specify a custom height and width for a plant on the plant’s Size property page. Note that if you do this, however, the plant’s size changes in both 2D and 3D regardless of the Planting Age setting on the Plant Info page.
Note: If you just want to see plants at a different maturity level (i.e. change their age), you should change their planting age instead. You can also apply an overall age change to your landscape.
To change the size of a plant:
Select the plant whose properties you want to edit.
Right-click and select Properties, or select Edit > Modify Elements > Properties.
In the Plants dialog, select the Size tab.
Set the Size from encyclopedia option to No.
To change the width of the plant, enter a value in the Width edit box.
To change the height of the plant in 3D view, edit the value in the Height edit box.
Click OK.