If you want the vibrant early yellow that Forsythia offers, but don’t really have the space for a 10′ x 10′ shrub, consider one of the smaller or dwarf cultivars. These include a new Proven Winners introduction, Show Off™ Sugar Baby, which is supposed to top out at 30″ and bloom profusely. Slightly larger (36″ x 36″) is Starlet, in the same series. Forsythia x intermedia ‘Courdijau’, sold as ‘Golden Peep,’ comes from a French breeding program, and is listed as growing 30″ high by 36″ wide. Forsythia x intermedia ‘Courtacour’ (Goldilocks) is from the same source, and features a slightly richer yellow and a spikier habit than “Golden Peep.” It also grows a little higher to 36″. Gold Tide (Forsythia x ‘Courtasol‘) is described as a fast grower that will reach 36″ in height and up to 6’ laterally. Any of these cultivars might be a good choice for a shrub border or for a tight foundation planting with full sun.
Frankly, many of the common Forsythias are not that interesting when out of flower (I’m being kind with this assessment). Some F. x intermedia cultivars do provide fall color, (F. x intermedia ‘New Hampshire Gold’ is a good example)but their summer and winter forms are less than exciting. Few Forsythia are really attractive in winter, but there are some forms with ornamental foliage that are worth considering.
‘Fiesta’ is a variegated form with red stems. I’ve been unable to find an illustration of this plant in winter, but the summer leaf variegation – lemon and lime – looks quite showy against the cherry-red stems. The flowers are typical. ‘Citrus Swizzle’ also has variegated leaves, and it has a more formal, patterned structure to its branches that would make it worthy of garden space even if it didn’t bloom (it’s a sport of F. viridissima ‘Bronxensis’, described in some references as a sparse bloomer.) There are several variegated forms of F. x intermedia that seem to come to life in fall, including ‘Susan Gruninger’, ‘Fords Freeway‘, and ‘Albovariegata‘. A cut-leaved cultivar, ‘Tremonia,’ was discovered in Germany and distributed in the United States by Boston’s Arnold Arboretum. F. viridissima var. koreana ‘Kumson’ is an especially interesting plant, first brought to the attention of Western nurseries in 1999. Unlike the patterns exhibited by the other Forsythias mentioned here, Kumson’s variegation is confined to the veins of the leaves, resulting in an eye-popping network of creamy white over dark green. There’s nothing else quite like it in the genus, or even in temperate horticulture.
Fit the Forsythia to the garden. The late Donald Wyman, Horticulturist at the Arnold Arboretum for many years, had this to say about the treatment of Forsythias in the landscape:
Unfortunately many public plantings of Forsythias are sadly mutilated because of lack of intelligent care in pruning. Forsythias should be given plenty of room in which to grow and expand. They should not be crowded closely together for any reason except to make a good, dense bank planting where the whole object is to cover the ground. Many times when a single bush is used, it will be placed only two or three feet from a walk when actually it should be placed 8 to 10 feet from the walk, in order to give the plant plenty of room to expand fully at maturity. If the plants are pruned from the side, this necessarily cuts off the lovely drooping branches and spoils the entire effect, leaving only the unsightly base and a few branches ending prematurely in mid-air when they should be allowed to arch gracefully to the ground.
You can read this quotation, and much more about the horticultural history of Forsythias, here. Special thanks to Forestfarm Nursery and Hoot Owl Hollow Nursery, both of whom sell many of the cultivars recommended here, and who kindly gave permission for the use of photographs from their catalog.