Ok, XFROG plants are not Vue's  "Solid Growth" .veg plants.

XFROG plants are meshes, where as Solid Growth plants are Vue specific tech that lets each plant be different...they aren't as detailed as an XFROG plant (*), but, they are oticably different, each one, hence Vue ecosystems look so good.

XFROG plants you save and load as you would any other mesh object: import into Vue and save as a .vob file for late ruse. Or, as FrankT says, XFROG plants should come withthe .vobs already made for ya, so, just copy & paste into yer Vue object folder of choice :)
(Usually "Static Plants", static as in "frozen", meshes)

(*) Note, you can increase the quality of individual Vue veg plants, edit them and increase polygon count ;)

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