Plant Taxonomy of Forsythia Bushes:
The plant taxonomy of the forsythia bushes with which I deal in this article is Forsythia x intermedia. This is a hybrid of greenstem (F. viridissima) and a weeping type (F. suspensa). The plants are sometimes given the common name, "border forsythias" or, more rarely, "golden bells."
Forsythias are deciduous flowering shrubs.
USDA Plant Hardiness Zones:
Forsythia plants are hardy to planting zone 5.
Characteristics of Forsythia Bushes:
These early bloomers sport the vibrant yellow flowers that have become a fixture of our spring dreams. Their flowers precede their leaves. They are fast-growing shrubs with an upright and arching form. Sunrise forsythia (Forsythia x intermedia 'Sunrise') is more compact than many forsythia shrubs, growing 4-6 feet tall with a spread of 3-5 feet. By contrast, Forsythia x intermedia 'Meadowlark' grows 8-10 feet tall. In between is Forsythia x intermedia 'Northern Gold', at 6-8 feet tall.
One knock against this shrub is that it is a one-hit wonder, providing great color while in bloom in spring but little else for the rest of the year. Admittedly, one 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 forsythia will sometimes surprise you with nice purplish leaves in autumn).
If you were consistent in denying plants a spot in your landscape based on this objection, however, you'd end up missing out on some of the most magnificent specimens of the landscaping world.
See below under "When to Prune Forsythia Bushes." 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. Through regular pruning, you can shape forsythia bushes to conform to a more regular shape if you so choose.
Even if you don't prune your shrub regularly, you may wish to keep an eye on its spread, at least. For, when one of the branches makes contact with the soil, there is a good chance that it will put down roots on the spot. You can look at this offspring of the original shrub as either a bonus or an intruder, depending on your perspective:
- It's a bonus if you wish to propagate the plant, because you can simply cut the branch in question (thereby severing ties with the parent plant), dig up the offspring by the roots, and transplant it wherever you wish (or simply leave it alone if you want a bigger display and have sufficient space).
- But it's an intruder if you have a small yard and prefer well-behaved plants that don't spread on their own.
Sun and Soil Requirements:
Forsythia plants grow best in full sun and a 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.
When to Prune Forsythia Bushes:
Pruning of forsythia bushes is best done just after they've finished putting on their flower display in spring because they bloom on the prior year's growth (pruning either too late or too early interrupts the growth/blooming cycle).
Begin by pruning 1/4 to 1/3 of oldest branches, pruning them right down to the ground. This will encourage new growth and a more compact form. Beyond this "renewal" or "rejuvenation" pruning, you can also selectively cut newer branches in order to improve upon the overall shape of your forsythia plants. [Note: Some authors draw a distinction between rejuvenation and renewal pruning, reserving the former term to denote a more drastic operation, whereby the entire plant is cut right down to the ground.]
Remember that annual pruning is by no means mandatory. If you're happy with your forsythia shrubs as they are, you may wish to go several years between prunings. Note also that there's 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's easiest to tell the newest branches apart from the older. Only the older branches will have blooms; the first-year branches won't have any yet, so you have a graphic reminder to avoid pruning them.
Uses for Forsythia Shrubs in Landscape Design:
Border forsythias, as the name suggests, are often used to demarcate property boundaries. They are also often used as a "living wall" privacy fence for summer and fall, after they have fully leafed out. They can also be used as specimens for spring and for erosion control on slopes.