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 add as many 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. Forsythias are fairly tolerant of poor garden soil, and they have some drought tolerance once 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. A natural look can be entirely appropriate for shrub borders alongside wooded areas.
Light
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.
Soil
Forsythias prefer loose, well-draining soil—however, these tough plants show tolerance for clay soil, too. They are not particularly picky about their pH levels and can thrive in both acidic and alkaline soil blends. Good drainage is important, however, so amend compact soils as needed.
Water
The bushes grow best in moderately moist soil, but they can handle some drought once they’re established. Water new forsythia plants regularly (at least 2 inches of water a week) until they’re established, 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 as well (however, many varieties do not respond well when winter temperatures fall below minus 5 degrees Fahrenheit). If exposed to prolonged periods of extreme cold, 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.
Fertilizer
Don’t fertilize your forsythia bush until it is about a year old and appears to be in good health. At that point, you can spread approximately a cup of granular fertilizer at the shrub’s base every few weeks throughout the spring and summer.
Types of Forsythia
There are many varietals within the forsythia genus, offering different 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 of the most common forsythias include:
Forsythia x intermedia ‘Sunrise’: This compact shrub grows to be between 4 and 6 feet tall and wide. Its flower buds are able to withstand colder winter temperatures than many other forsythia varieties.Forsythia x intermedia ‘Meadowlark’: A varietal that 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’: A shrub that 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’: This varietal that boasts larger yellow flowers and leaves that turn an attractive yellow with purple tinges in fall.Forsythia ‘Courtasol’: A dwarf shrub, it 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 suspens: The pure species known as weeping forsythia has pendulous branches that can grow as long as 10 feet, which can be trained up a trellis if you wish.Forsythia ‘Arnold Dwarf’: This low-growing, spreading shrub reaches only 2 to 3 feet tall, but spreads nicely. Though it does not flower as profusely as other varieties, it’s an excellent ground cover plant for larger areas.Forsythia x ‘New Hampshire Gold’: An excellent cold-hardy shrub, hardy through zone three. It grows 4 to 5 feet tall and boasts an attractive red color in the fall.Forsythia ‘Northern Sun’: A good shrub for colder climates (zones 4 and south), it grows 10 feet tall and 9 feet wide, with clear yellow flowers.
Pruning Forsythia
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. KenWiedemann / Getty Images 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.
Propagating Forsythia
Propagating forsythia plants is the best way to multiply your supply, short of heading to a nursery to get more mature plants. The ideal way to propagate forsythia is through a stem cutting in early to mid-summer. Here’s how: An even easier way to create new forsythia shrubs is by layering. Find a long branch on the existing shrub, bend it so that a node touches the ground, and gently scrape away the bark above and below the node. Secure the bent branch with a rock so it touches the soil, and wait. Roots should form along the layered branch, and you can then cut the branch from the parent shrub, dig up the rooted branch, and plant in a new location.
Common Plant Diseases
Forsythia shrubs can be prone to knobby galls forming along the stems, as well as 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.
How to Get Forsythia to Bloom
If you find yourself missing out on forsythia’s signature bright blooms, there may be a few causes to blame. One of the most common issues for a lack of blooms is improper pruning. Forsythia set bloom on old wood, so any pruning should be done before that happens. Prune immediately after blooming in spring. If you wait until late summer or early fall, you run the risk of pruning off next year’s flowers, which will leave you with a rather bare bush for the following season. Another reason why your forsythia bush may not be blooming adequately is due to a lack of light. Forsythia bushes needs at least six hours of light daily (on average—a few days here or there with less won’t be a huge issue). If you have a few pesky bushes that just aren’t blooming, take some time to observe how much light your plant gets. If you can, trim back nearby trees that may be blocked the light to allow more sun to reach your bush.
