"In the evolutionary approach, engineers “prune” design iterations as they evolve and grow under the force of random mutations, directing the path of evolution in the same way one might clip a Bonsai tree to achieve a desired shape, or breed a new form of tulip."

mmmm, I suspect a better analogy than gardening is genetic engineering. Random mutations are part of it, as are pruning and cultivating, but more aggressive hacks are used too.