Roses failing to bloom? Here are 4 possible reasons why.
“Many of my roses, such as David Austin, are blooming less after August but growing lush without any buds. What is the reason for these blind shoots?”
— Benjamin Anderson, Winnetka
It has been an extraordinary season for roses at the Chicago Botanic Garden this year, with lots of flowers continuing even at this late date, which is not typical. Your roses should have been performing in a similar manner. There may be issues in your garden or how you have been caring for them.
Roses perform best in full sun, so if the shade levels in your garden have increased because of adjacent trees or large shrubs, then you will generally see reduced flowering.
The amount of shade will increase over the course of the growing season as plants grow taller and denser.
I see increasing shade in many gardens affecting the performance of full sun-loving plants, resulting in reduced flowering and thinning foliage. On the other hand, the foliage of shade-loving plants, such as hosta and pachysandra, in too much sun will typically start to yellow and burn (turn brown).
Plants that are overfertilized will put on lots of lush, green growth at the expense of flowers. Roses do feed heavily, but if overfertilized, will put on lots of growth with no flowers or greatly reduced flowering.
If the roses are grafted, non-flowering rootstock suckers could be taking over the plants, although this would tend to occur more sporadically on a couple of plants in a large planting of roses, versus all of the plants.
If you can eliminate shade, overfertilizing and rootstock suckers as causes for the lack of flowers, then you may have an infestation of rose midge.
The adult rose midge is a very small insect which most gardeners will not be able to see and looks somewhat like a mosquito. The female deposits eggs in or under the new leaf tips of a developing bud; the larvae look like very small white worms feeding on the base of the developing bud, which stops its development and often causes it to turn black and fall off.
This stem will not produce a flower for another bloom cycle, and when repeated throughout a rose planting, there will be an absence of flowers like in your garden. You will need to implement a preventive spray program next year, if you determine rose midge to be the problem with your roses.