Forsythias are deciduous flowering shrubs (bushes) known for their long branches that fill with brilliant yellow blooms early in spring. Forsythia belong to the olive family and grow in USDA plant hardiness zones 5 through 8.
Taxonomy and Botany of Forsythia Bushes
The plant taxonomy of the "border forsythia" bush is Forsythia x intermedia. This is a hybrid of greenstem (F. viridissima) and a weeping type (F. suspensa). They are also given the common name "golden bells." F. suspensa and most other species are native to the Far East.
Forsythia Bush Characteristics
These early bloomers sport the vibrant yellow flowers that have become a fixture of our spring dreams. Their flowers precede their leaves, which means that you get a really good look at the blooms because there are no leaves to block your view of them. They are fast-growing shrubs with an upright and arching form.
The Sunrise cultivar (Forsythia x intermedia 'Sunrise') is more compact than many forsythia shrubs, growing 4 to 6 feet tall with a spread of 3 to 5 feet. By contrast, Forsythia x intermedia 'Meadowlark' grows 8 to 10 feet tall. In between is Forsythia x intermedia 'Northern Gold', at 6 to 8 feet tall. Even more compact than 'Sunrise' is 'Courtasol' (Gold Tide) at 1 to 2 feet in height, with a spread of 1 to 4 feet.
One knock against this shrub is that it is a one-hit wonder, providing great color while in bloom in early spring but little else for the rest of the year. Admittedly, most gardeners would not grow it for its leaves alone, as there is nothing remarkable about their shape or color. Nor are they known for their fall color, although forsythias will sometimes surprise you with nice purplish leaves in autumn.
Growing Forsythia Shrubs
Forsythia plants grow best in full sun and well-drained soil. But these tough plants show some tolerance of clay soils, too. Water new transplants well to get them established; thereafter, water needs are moderate.
If left to their own devices, forsythia plants take on a rather wild-looking shape, as branches shoot out this way and that. Most people prefer this wild look, pruning forsythia bushes only sparingly. But if you prefer a neater look, you can prune the bushes to conform to a more regular shape.
Even if you do not prune your shrub regularly, you may wish to keep an eye on its spread. When a branch makes contact with the soil, it often puts down roots on the spot, creating a new shrub. You can look at this offspring of the original shrub as either a bonus or an intruder, depending on your perspective. If you wish to propagate more plants, you can simply cut the branch that rooted, dig up the offspring by the roots, and transplant it wherever you wish. Or, your can simply leave it alone if you want to expand the mother plant.
When to Prune Forsythia Bushes
Pruning of forsythia bushes is best done just after they have finished putting on their flower display in spring because they bloom on the prior year's growth. If you prune them either too late or too early, you could lose flower buds and end up with a poor display.
Begin by pruning 1/4 to 1/3 of the oldest branches, cutting them right down to the ground. This will encourage new growth and a more compact form. Beyond this "renewal" pruning, you can also selectively cut newer branches to improve upon the overall shape of your forsythia plants.
Keep in mind that annual pruning is by no means mandatory. If you are happy with your forsythia shrubs as they are, you may wish to go several years between prunings. Note also that there is an additional incentive for pruning forsythia shrubs just after their spring blooms start to fade, beyond wishing not to interrupt their blooming cycle. This is the time when it is easiest to tell the newer branches apart from the older. Only the older branches will have blooms. The first-year branches will not have any yet, so you have a graphic reminder to avoid pruning them (it is the growth of these fresh, new branches that you want to foster).
Uses of Fosythia in Landscape Design
Border forsythias, as the name suggests, are often used to define property boundaries. They can be grown along a fence (to dress it up), or they can be planted to form a border all on their own. These beautiful flowering shrubs are also often used as a "living wall" privacy fence for summer and fall, after they have fully leafed out. In addition, they can be used as specimens for spring, for erosion control on slopes, and in foundation plantings. The weeping type (F. suspensa) can be trained to grow as a vine on a trellis or planted behind a retaining wall and allowed to cascade over the side.
For a more novel use of this plant, you can force forsythia by cutting branches and bringing them indoors in late winter. Like forcing pussy willows, this is a great way for the impatient to gain an early taste of springtime.