Forsythia is a genus of spring flowering shrubs that burst into bloom in early March before their leaves appear. However, they are best known by their common name of yellowbells. Yellowbells (Forsythia x intermedia) are deciduous, mounding shrubs that can grow as large as 10 feet tall by 10 feet wide. Many newer mid-sized cultivars may grow to 5 feet tall by 6 feet wide, yet some recent releases only grow to 1½ by 3 feet at maturity. These smaller cultivars are perfect as accent plants in cottage style, perennial landscapes, and the faster growing, larger cultivars make excellent, impervious hedges. They are deer resistant, make nice nesting sites for songbirds, are easy to grow, and require little maintenance.
The flower buds form during the late summer and early fall. Then in the early spring, they produce their bell-shaped flowers. For the best shrub shape and maximum flowering, plant yellowbells in full sun.
Cut branches may be brought indoors during the winter for forcing, i.e., to make them bloom earlier. Place the branches in vases of water indoors, and they will begin to flower in about 10 days.
Prune yellowbells annually as needed during the spring after flowering. Spring pruning allows time for flower buds to form for next spring’s bloom. If pruning is required, prune out 1/3 of the older canes and prune these to a few inches tall. Alternatively, for a very over-grown shrub, prune the entire plant down to 3 or 4 inches tall. This will rejuvenate the yellowbells; although, it might take two years to re-bloom. Avoid ruining the natural mounding shape by shearing them into squares or balls.
For more information on cultivars and culture, see HGIC 1064, Forsythia.