Question of the Week: February 17, 2022
“When should I fertilize my spring-flowering shrubs and vines? Will they bloom better if I feed them now?”
This is not the time to apply fertilizer to spring-flowering shrubs and vines. Their buds are already in place and will soon be expanding (if they’re not already doing so). Feeding now would not help that.
Spring and early summer feedings…
As soon as they have finished blooming this spring apply a high-nitrogen (for sandy soils) or all-nitrogen (for clay soils) lawn-type fertilizer to promote strong growth of new stems and leaves. If they need any pruning and shaping, that’s the time to do that, too.
Repeat that application two months later. That would put you into early summer. They will still be growing strongly at that time.
Early fall feedings…
If you are going to apply a fertilizer to stimulate flower bud setting on these spring-blooming shrubs and vines, that would be made in early September and it would be of a product containing a higher percentage of phosphorus, middle number of the 3-number analysis.
However, there is an important side issue. Clay soils tend to accumulate phosphorus to excessive levels. (Not as commonly a problem in sandy soils that don’t retain nutrients.)
Before you start adding high-phosphate fertilizers, have your soil tested every few years to be sure that’s not happening. If it is, just switch back to the same fertilizer you used in the spring.