The standard advice for pruning spring-blooming shrubs is to prune them no later than two weeks after they’re done blooming. This is because most spring-flowering shrubs, at least, all those commonly grown, develop their flower buds on the previous year’s wood. So if you prune them in high summer, or autumn, you are cutting off the wood that has the next spring’s flowers.
Pruning forsythia in March has its advantages
However, it is far easier to see the structure of the shrub you are pruning in late winter, when the temperatures have moderated somewhat but the shrub hasn’t leafed out or started blooming yet. And, in the case of forsythia, you can bring the prunings indoors, stick them in a container of water, and, in about a week, have forsythia blooming in the house. These in the photo were cut about a week ago, on one of those nice days just before winter returned.
Since the forsythia outside will be blooming in another week (or two, weather depending), some people might wonder, “Why bother?” I can only speak for myself. At a time when the mild weather has vanished and interminable gray days with flurries have taken its place, forsythia blooming in the house is incredibly cheering. And if past experience holds true, it will not dampen in the least my appreciation of forsythia blooming outside later this month.
And I’ve accomplished two goals at once: I thinned out a shrub that needed it and brought in blooms for the house. According to this article, forsythia branches can be brought in as early as January. Hmph. Maybe if there’s a spring thaw about then. I personally can’t bring myself to do much more than run down the driveway to our rural mailbox and run back with the mail when the wind is blowing and the snow is flying. Not to mention that the branches that need pruning might be under snow. Also, the closer in time to the natural blooming of the shrub, the better the results.
The fact that forsythia blooms on old wood is one reason why some northern gardeners get little or no bloom on their shrubs. (The other big reason is growing in the shade. Unless you pruned all the flowering branches off. Duh.) Those delicate little buds don’t always make it through the winter. I was sure glad I found this out before I plunked down my plastic for the forsythia of my childhood, ‘Lynwood Gold.’ ‘Lynwood Gold’ is rated hardy to Zone 4, but it’s only bud-hardy to Zone 5–in a good year. I grow ‘Meadowlark,’ which is supposedly bud hardy to -35. (That’s minus. thirty-five. degrees. Fahrenheit.) Fortunately, I haven’t had to personally verify this. You can also look for ‘Northern Gold, ‘Northern Sun,’ ‘Vermont Sun,’ ‘New Hampshire Gold,’ or ‘Ottawa,’ which are all supposed to be bud-hardy to Zone 4.
For those of you who save all your back issues of gardening magazines, here’s some more information on forcing branches:
- Ann Lovejoy, “Boughing to Spring,” in Horticulture (February 1994), pp. 44-48
- Wayne Winterrowd, “A Harvest of Winter Color,” in Horticulture (November 1998), p. 32-38