What is the best fertilizer for barberry bushes?

Compost is the best fertilizer for barberry bushes (Berberis spp).

Specifically, barberry bushes can handle a variety of environmental and soil conditions. They do not need special fertilizer attention when they grow in grass, ground cover, lawn or turf that regularly is treated with fertilizer. But for those who feel more comfortable doing so, compost is a wise choice. It provides a slow but direct and steady release of nutrients back into the soil for intake for the barberry's roots.