Forsythias are a genus of deciduous flowering shrubs that belong to the olive family. These low-maintenance, fast-growing shrubs feature an upright, arching form. They are known for their long branches that fill with brilliant yellow blooms early in the spring. The flowers precede their leaves, which means you get a good look at the blooms with no foliage to block your view.
Bees and butterflies love forsythia, and they provide a cheerful backdrop, border, or centerpiece for any yard. Some smaller forsythia varieties only stand a couple of feet tall with a slightly wider spread while many of the larger varieties can reach around 10 feet in height and spread.
Forsythias are fast-growing shrubs that can grow as much as 24 inches in a year, especially the larger varieties. They are best planted in late fall or early spring while the plants are still dormant, but gardeners in frost-free climates can plant them in winter, as well.
|Botanical Name||Forsythia spp.|
|Common Name||Forsythia, golden bells|
|Plant Type||Deciduous shrub|
|Mature Size||2–10 feet tall, depending on variety|
|Sun Exposure||Full sun to part shade|
|Soil Type||Loose, medium moisture, well-draining soil|
|Soil pH||5.0–8.0 (acidic to alkaline)|
|Hardiness Zones||5 to 8 (USDA)|
Forsythia bushes are often used as a living privacy wall in the summer and fall after they have fully leafed out. In addition, they can be used for erosion control on slopes and in foundation plantings. The weeping type (Forsythia suspensa) can even be trained to grow as a vine on a trellis or planted behind a retaining wall and allowed to cascade over the side.
Forsythias are fairly tolerant of poor garden soil, and they have some drought tolerance once they’re established. As long as you situate them somewhere that gets a lot of sunlight, they should grow well for you. The biggest burden when growing forsythia is to keep these fast-growing shrubs pruned to maintain the desired shape and size. But even this can be ignored if you like a somewhat wild-looking shrub, as many people do. An unkempt look can be entirely appropriate for shrub borders along wooded areas.
Forsythia bushes grow best with at least six hours of direct sun on most days. If your plant gets less sun than this, it might not produce as many flowers.
Forsythias prefer loose, well-draining soil. However, these tough plants show some tolerance for clay soil, too. They have a good tolerance for both acidic and alkaline pH levels.
The bushes grow best in moderately moist soil, but they can handle some drought. Water new transplants regularly until they're established. And then only water if you have an extended period with no rainfall.
Temperature and Humidity
Forsythias prefer slightly humid climates. If it's too dry they might not flower, and if it's too moist they might wilt. They're happiest when the temperature is between 55 and 70 degrees Fahrenheit, but they're fairly hardy in colder temperatures. However, many varieties do not respond well when winter temperatures fall below minus 5 degrees Fahrenheit. Flowering for the following spring may be absent or reduced, though the plant generally recovers and returns to normal flowering a year later. Northern gardeners will want to make sure to choose a variety known to have good hardiness in their climate zone.
Don't use fertilizer until your forsythia bush is about a year old and appears healthy. Then, spread about a cup of granular fertilizer at the shrub's base every few weeks in the spring and summer.
There are many species varieties within the forsythia genus, offering varying sizes and shapes. The varieties known as 'intermedia' are hybrid plants achieved by crossing weeping forsythia (F. suspensa) and greenstem forsythia (F. viridissima), with traits that are "intermediate" between the two parents.
Some favorites forsythias include:
- Forsythia x intermedia 'Sunrise' is a compact shrub, growing around 4 to 6 feet tall and wide. Its flower buds are able to withstand colder winter temperatures than many other forsythia varieties.
- Forsythia x intermedia 'Meadowlark' grows around 7 to 10 feet tall with a similar spread. It's known for having very few issues with pests and diseases.
- Forsythia x intermedia 'Kolgold' matures at around 4 to 5 feet in height and spread. It sports larger flowers than most forsythia bushes, at roughly 1 inch across.
- Forsythia x intermedia 'Lynwood Variety' has somewhat larger yellow flowers and the leaves turn an attractive yellow with purple tinges in fall.
- Forsythia 'Courtasol' is a dwarf shrub that reaches just 1 to 2 feet tall with a spread of around 1 to 4 feet. It produces profuse light yellow flowers in the early spring.
- Forsythia suspensa is the pure species known as weeping forsythia. It has pendulous branches that can grow as long as 10 feet; they can be trained up a trellis if you wish.
- Forsythia 'Arnold Dwarf' is a low-growing, spreading shrub that grows only 2 to 3 feet tall, but spreads nicely. Though it does not flower as profusely as other varieties, it is an excellent ground cover plant for large areas.
- Forsythia x 'New Hampshire Gold' is an excellent cold-hardy shrub, hardy through zone 3. It grows 4 to 5 feet tall and has attractive red color in the fall.
- Forsythia 'Northern Sun' is another good shrub for colder climates (zones 4 and south). It grows 10 feet tall and 9 feet wide, with clear yellow flowers.
If you wish to propagate more forsythia plants, you can simply take a stem cutting, root it, and transplant it wherever you wish. You also can allow the parent plant to spread on its own. When a branch makes contact with the soil, it will often put down roots on the spot, creating a new shrub.
To root a cutting, take a 4- to 10-inch long stem cutting after flowering is completing and when the shrub has leaves. Remove the bottom leaves, then plant the cutting in a moistened mixture of peat moss, perlite, and sand. Roots will grow from the buried nodes.
Mist the cuttings daily until the roots are about 1 inch in length, which will take at least a month. At this point, transplant the cuttings into individual pots for continued growing. Grow the plant in a pot in a controlled outdoor environment for one or two seasons before planting it in a garden location.
If left to their own devices, forsythia bushes can take on a rather wild-looking shape, as branches shoot out in random directions. Many people prefer this wild look, and annual pruning is by no means mandatory. If you're happy with your bush's shape, you can go for several years without pruning.
However, if you like a neater look, you can prune your bush to conform to a more organized shape. Pruning of forsythia bushes is best done just after they have finished blooming in the spring because the following spring's flowers will bloom on wood produced the previous year. Thus, if you prune past the end of July, you run the risk of losing all the flowers for the following spring. This won't kill the plant, but it means you'll have drab shrubs for a year.
Begin by pruning roughly a quarter to a third 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.
Common Pests/ Diseases
Forsythia shrubs can be prone to knobby galls forming along the stems, and fungal twig blights. Both problems are best treated by removing affected stems. Twig blights can be prevented by keeping the plant well pruned to improve air circulation, and by applying a fungicide.
Unseasonable frost can kill the flower buds in climate zones that are borderline with the plant's hardiness rating. A variety rated for zone 5, for example, may occasionally lose its flowers in a zone 5 garden if an early cold spell hits. This will almost never kill the plant, and the flowers generally return after a year of no blooms.