Just when you don’t think you can stand another minute of bare branches or dead, brown-gray foliage, spring heralds its arrival in a burst of dazzling yellow. All over town, forsythias reassure us that the growing season really is at hand.
Originally from eastern Asia, where they have been cultivated for centuries, forsythias were collected for western gardens in the early 1800s. Most current garden varieties are hybrids of two species, Forsythia suspensa and F. viridissima. The problem is that the resulting cultivars aren’t reliably hardy in much of Colorado.
Happily plant breeders have been hard at work. ‘Northern Gold’ and ‘Northern Sun’ are both the product of a cross that includes a very hardy (but not very showy) Korean species. The resulting bushes retain the spectacular floral display of their other parentage, and survive down to USDA zone 4, or even 3 with a thick mulch or good snow cover. That’s plenty of hardiness for the Front Range. ‘Meadowlark’ is another cultivar hardy to zone 4.
Grown for their early spring flowers, the shrubs aren’t all that ornamental the rest of the year. Finely toothed green leaves three to five inches long and one inch wide turn a dull purple right before they fall. The bare winter branches tend to look messy rather than attractive. Situate the shrubs where they can recede into the background once their bloom is over.
Forsythias come in a variety of sizes and shapes, but the most hardy ones are all rather large; given enough time, they can reach to the eaves and spread ten feet or more. Not every yard has enough space for this spring beauty.
Besides adding yet another garden chore to the list, excessive pruning can ruin the shape of the plant and reduce flowering. Since the flower buds are set during the previous growing season, any pruning should be done immediately after bloom, before the plants leaf out. Every spring, cut out about a third of the old wood at the base of the plant to retain a natural appearance and encourage new growth.
Other requirements are simple—full sun, amended garden soil, and “average” water. Irrigate regularly (or choose a drought-resistant alternative such as Golden Currant). The plants are rarely bothered by insect pests, and they are listed as deer and rabbit resistant (although a hungry deer will eat pretty much anything).