Forsythia is a deciduous flowering shrub; it grows tall and full enough to be used as a privacy hedge. The forsythia shrub produces multiple trunks, and many branches. The leaves are light- to mid-green and oval. Forsythia blossoms are bright sunny yellow. For the shrub to develop optimally, it is important to prune the shrub each year.
Prune after the forsythia shrub has already bloomed. Forsythia blooms during March, and pruning should be done immediately after it blooms. Late March is the ideal time to prune.
Cut off last year's wood with gardening shears. Forsythia produces blooms on year-old wood, and will never blossom on old wood. Cut trunks that flowered this year down to the soil line. The shrub will still look full, because it has more than one trunk.
Cut off dead wood, and any branches that look spindly or sickly. Trim back branches that extend out further than the natural lines of the bush.
Shape the forsythia, if you desire. Forsythia takes on a natural tapered shape, but some people like to trim their forsythia bushes into box or orb shapes.