It is actually common use in English, and perfectly fine grammar, for an adjective to apply to multiple nouns. Some examples:
The nurses have clean sheets and blankets.
Those are very ripe apples and oranges.
My friend has very pretty cats and dogs.
Mage Wars makes use of this, which allows them to save some space on the cards. So, in your question, the descriptive use of the Vine subtype applies to both creatures and conjurations. ACG actually did a really good job breaking it down in detail how this works.