OVERGROWN

To grow beyond one's boundaries or containment, or beyond the proper size.

To grow over; (of one thing) to cause (a second thing) to become overgrown (with or by the first thing).

Having large numbers of plants which have become too big, and are hence spoiling the picturesqueness of a garden.

Having grown bigger without developing maturity or changing character.

"He spends so much money on new technology: he's like an overgrown schoolboy buying toys."