 Culture Notes
Forsythia will grow in part shade, but needs full sun to bloom the best. Prune the flower shoots near the old wood as soon as the flowers fade. This pruning will keep the shrub neat and compact.
Forsythia is one of the most common spring flowering shrubs, with its yellow flowers occurring before the leaves appear. Plant in a sunny growing area with a well-drained soil. This rapid grower transplants well.  Thin occasionally by cutting off old wood at ground level. After a severe winter, only the protected lower branches have flowers. Forsythia tolerates city conditions but not crowding.
Planting and establishing shrubs
The most common cause of young plant failure is planting too deep. Plant the root ball no deeper than it was in the nursery. In most instances, the root flare zone (point where the top-most root in the root ball originates from the trunk) should be located just above the landscape soil surface. Sometimes plants come from the nursery with soil over the root flare. If there is soil over this area, scrape it off. The planting hole should be at least twice the width of the root ball, preferably wider. In all but exceptional circumstances where the soil is very poor, there is no need to incorporate anything into the backfill soil except the loosened soil that came out of the planting hole. Never place ANY soil over the root ball. If a row or grouping of plants is to be installed, excavating or loosening the soil in the entire bed and incorporating organic matter enhances root growth and establishment rate.
Weed suppression during establishment is essential. Apply a 3-inch thick layer of mulch around the plant to help control weed growth. Keep it at least 10 inches from the trunk. If you apply it over the root ball, apply only a one or two inch layer.  This allows rainwater and air to easily enter the root ball and keeps the trunk dry. Placing mulch against the trunk or applying too thick a layer above the root ball can kill the plant by oxygen starvation, death of bark, stem and root diseases, prevention of hardening off for winter, vole and other rodent damage to the trunk, keeping soil too wet, or repelling water. Regular irrigation through the first growing season after planting encourages rapid root growth, which is essential for quick plant establishment.
Pests, Diseases and Damaging Agents
Pests:Â Few lethal pests bother forsythia.