Forsythia

Closely related to the lilacs are the Forsythias, of which there are 11 species and quite a number of hybrids and cultivars. All but one are native to cold parts of Asia- mainly Siberia, Korea, and China. The genus is frequently mispronounced- people usually say For-SITH-ee-uh and the correct pronunciation is For-SYTHE-ee-uh. William Forsyth (1737-1804) was a very prominent Scottish botanist and one of the founding members of the Royal Horticultural Society. The genus is named for him.

Forsythias normally grow anywhere from 3-10 ft. tall and 6-8 ft. wide. Occasionally, they can be as much as 20 ft. tall. The brilliant yellow flowers appear in early spring, often when there is still snow on the ground. Blooming lasts for 10-14 days, and when flowering is finished the leaves emerge. You would think that for something so closely related to lilacs that they would be fragrant, but they are completely devoid of scent. 

Forsythia are highly adaptable, very easy going shrubs and they are great for both beginners and experienced gardeners. Give them full sun and well drained soil to be at their best. Although they can tolerate drought and neglect like lilacs can, they respond better to good moisture conditions and love. They are not as long lived as lilacs, lasting only about 40 years, but should be given a well chosen spot. Forsythias will not sucker like lilacs do but they have very extensive root systems and digging out an established plant (either dead or alive) is difficult.

So the question is, where do you plant a Forsythia? Full sun for sure. They aren’t prone to pest or disease issues but they have little tolerance for shade. Ideally, you want them in a spot where you will be able to see them from your kitchen window or another good vantage point because they are one of the first shrubs to flower, but it when they do flower it may not yet be nice enough to be out and about in the garden. They also benefit from being in a sheltered location, especially where snow might drift up and help protect the branches.

Given their moderate to large size, they are a hard thing to just discreetly “tuck in” somewhere. Finding a good spot, however, is critical if you want them to flower. Forsythias can handle both salt spray and pollution and they are good candidates for city gardeners. The leaves, though not especially flashy, will sometimes color up in the fall- the color is variable, and can range from yellow to plum purple.

They will absolutely tolerate being pruned, but beward that bad pruning makes them look unnatural, especially in winter. We do not recommend shearing forsythias into hedges or balls. Every few years, going in and removing any and all wood that is older than three to four years is a good idea because they can become quite “twiggy” with age.

Cutting a few branches (discreetly) in late February or early March and using them for forcing is also fun. Just put them in a vase of water in a warm room and they’ll soon burst into flower, often several weeks or a month before they are blooming outside! These branches will often form roots in the vase, and these can easily be planted if you wish. Forsythia is one of the easiest shrubs to propagate from cuttings or layering, and branches stuck in the ground and kept moist will usually grow.

The first Forsythia to reach European shores ended up in Holland in 1833. Others soon followed, and Dutch botanists discovered that they hybridized quite easily. This led to a number of varieties being developed, all of varying hardiness due to very diverse parentage. Most of these forsythias claimed parentage heavily from Forsythia ovata, which is native to Korea and very hardy. The hybrids, dubbed Forsythia x intermedia were very hit and miss until the ‘Lynwood’ variety was introduced.

Still available and sometimes called ‘Lynwood Gold’, this variety was soon the darling of the gardening world. It was vigorous and flowered profusely, it was reasonably compact, and it was extremely cold hardy. From this one, dozens of new hybrids and cultivars have been developed. The ‘Lynwood’ forsythia soon made its way over to North America, and tests eventually proved that it was hardy to about zone 4, possibly zone 3 in a protected spot.

An interesting thing was soon proved about these shrubs. While the shrub itself is largely hardy, they are not entirely “bud hardy”. This means that the plant itself can tolerate much colder temperatures than the developing flower buds. This year’s blossoms appear on last year’s wood, so the flower buds actually develop over the previous growing season. The plant itself might be hardy to 30 or 40 below; the flower buds may only be hardy to -25.

This means that if we have a particularly harsh winter, the shrub itself will survive but it will not bloom. In cold climates such as the prairies, you will sometimes see forsythias that only bloom on the very bottom branches. This is where the branches were buried by snow and thus protected from the worst of winter gales, while the upper branches are devoid of blossoms.

Out of the two dozen or so cultivars of forsythia available to gardeners, only a very few of them are bud hardy enough to be worth trying on the Canadian prairies. By the far the most reliable is ‘Northern Gold’. In 1962 at the Ottawa Experimental Farm, a cross was made between Forsythia ovata and a variety called ‘Ottawa’. One of those seedlings was very compact and vigorous and flowered better than any forsythia they had ever seen. It was also much, much hardier. Official trials began at the Morden Research Station in 1971, and it was the hardiest and best forsythia they had ever worked with. It was introduced to the public in the early eighties and remains a top seller and is without question the most reliable. It grows 6-8 ft. tall and wide, but is occasionally as tall as 10 ft.  ‘Northern Gold’ is bud hardy to -39 Celsius, which means that if we have a week in January where it -48 due to wind chill, you’re likely going to lose some blooms. Don’t worry about it; it happens. This is still by far your best choice.

Your second best choice is ‘Meadowlark’. A joint introduction from the Universities of North and South Dakota, this variety is a bit more compact than ‘Northern Gold’ and resembles it so closely you are unlikely to be able to tell them apart. It is a vigorous grower, bud hardy to -35 Celsius, and the leaves often color up yellow in fall.

‘Northern Sun’ is occasionally offered, and it was introduced from the University of Minnesota. It grows 8-10 ft. tall and wide and is very sturdy, being bud hardy to -30 Celsius.

When you go to a garden center in the spring, you will often find other varieties of forsythia being offered, but for the most part, they are not recommended. Even if they survive, the probability of ever seeing flowers on them reliably is remote. Both ‘New Hampshire Gold’ (zone 4 at best) and ‘Kumson’ (a variegated form that is stunning but definitely not hardy) have been offered locally, as well as several of the weeping forms of forsythia, but none of them are recommendedon the Prairies. ‘Happy Centennial’, which is short and wide and almost a ground cover, as well as ‘Golden Peep’, a very cute little dwarf, have also been offered as “marginally hardy”. These have also been unsuccessful on the Canadian prairies.

Another common forsythia is a variety released from American plant breeding company Proven Winners, called ‘Show-Off’. Extremely compact and maxing out at around 5 ft. tall, it has extra large, very showy flowers and has been heavily marketed. It is listed as being hardy to zone 3, which it technically is, but it is not reliably bud hardy.

Overall, our best recommendation for reliable flowers is to plant ‘Northern Gold’.