Plant growth has different effects depending on the version
Overgrowth: The first effect causes normal vegetation
(grasses, briars, bushes, creepers, thistles, trees, vines, etc.)
within long range (400 feet + 40 feet per level) to become thick
and overgrown. The plants entwine to form a thicket or jungle
that creatures must hack or force a way through. Speed drops to 5
feet, or 10 feet for Large or larger creatures. (The DM may allow
faster movement for very small or very large creatures.) The area
must have brush and trees in it for this spell to take effect.
At the character's option, the area can be a circle with a
radius of 100 feet, a semicircle with a radius of 150 feet, or a
quarter circle with a radius of 200 feet. The character may also
designate areas within the area that are not affected.
Enrichment: The second effect targets plants within a range of
one-half mile, raising their potential productivity over the
course of the next year to one-third above normal.
In many farming communities, clerics or druids cast this spell
at planting time as part of the spring festivals.