I have one of each of the above, both 4yrs old and I cannot get either to bloom yet. Both in partial shade, moist soil. Never been pruned. each one is approx. 3feet tall.
How do I get them to bloom?
We live in Ottawa.
Thank you for contacting the Toronto Master Gardeners with your inquiry.
Both Forsythia and Bridal Wreath Spirea are shrubs that bloom in the Spring on old wood. This means that this year’s growth brings next year’s flowers. If you pruned your shrub in summer or fall, or you trim it to rigid dimensions, you have removed the growth that would have produced flowers. Since you mentioned that you haven’t pruned them then this is not the issue.
It could be the placement of your shrubs in your yard. Forsythias and Spireas bloom best in full sun (this means at least 6 hours), though they will take part shade. However, if yours is deeply shaded, it will not be as flamboyant as it would be in a sunnier position.
Too much nitrogen will turn your shrubs a full and lovely green, but they won’t bloom. If your shrubs are surrounded by lawn, the high nitrogen fertilizer you use on your grass may be hindering bud production. Adding more phosphorus, like bone meal, can help offset this.
A last reason for non-blooming is when the shrubs have gone through a particularly harsh winter, which damages the flower buds. Toronto’s hardiness zone is a 6b-7a, much milder than your area which is now classified as 5b. It is very likely that your flower buds were killed off due to insufficient snow fall or an unexpected spring frost.
If you still are having problems getting your Forsythia and Bridal Wreath to flower you may wish to contact the Master Gardeners in your area. Here is their link.