When growing roses (Rosa spp.), it's natural for petals to fall off your roses when blossoms die away at the end of a bloom period. Yet if you discover your roses are continually dropping petals before the flower has completely bloomed or soon afterward, it can indicate a problem. Petals might be falling off your roses for several reasons, including pests, weather and diseases. Once you identify the cause, you can take steps to address the issue, and therefore ensure your rose bushes are healthy and produce quality blooms all season long.
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Petals can fall off roses prematurely due to weather conditions, pest infestations or fungal disease. Roses naturally start to lose petals as the blooms get older.
Changing Weather Conditions
If weather conditions change rapidly from cool and damp to hot and dry, it can affect roses and cause petals to drop. Blossoms might partially open and then wilt and fall off when exposed to irregular weather patterns. Providing rose bushes with an additional layer of mulch and applying a potash-rich fertilizer or phosphate rock and green sand can lessen the impact of fluctuating temperatures and fortify your rose bushes.
Thrips on Roses
Thrips are small insects with extended bodies that eat bud bases and petals. They prevent buds from opening and cause blooms to be misshaped as petals weaken and fall. Thrips also damage rose leaves, causing yellow flecks, twisting and distorted appearances. Although they can be found on any rose bush variety, they frequently infest light-colored roses, such as white and pastels.
Check the petals for yellow-brown lines and tiny dark dots or bumps to confirm the pest's presence. Prune buds affected with thrips using disinfected pruning shears. Apply an insecticide to the entire bush to eliminate the insect. More than one application might be required to eradicate them from your rose bush entirely.
Rose Midges on Roses
While not common, rose midges can damage your growing rose bushes, affecting the rose buds and preventing the buds from opening, so they eventually brown and fall off. Rose midges are very small and somewhat resemble a mosquito. Look for very small white fly larvae that resemble a caterpillar near the base of the bud as the adult females lay their eggs in sepals of new flowers and in leaf buds. Midges can also be found among petals and sepals on an infected bush.
Pruning the rose bush can help control rose midges. Remove and dispose of all buds infested with midges. Spray the entire rose bush with an insecticide that contains either neem or spinosad. Both of these products will effectively eliminate midges from your rose bush.
Botrytis Blight Fungal Disease
Botrytis blight is a fungal disease that affects rose bush flowers, generally showing up during periods of cool, damp weather. The infection thwarts buds from opening, and over time, the buds become brown or shadowy gray in color and petals fall. It can cause leaves to form soft, brown spots. You might also notice cankers growing on the canes of your rose bush.
Cut off the infected buds. There is no treatment for the disease. As weather conditions change and turn hot and dry, the remaining, healthy flowers should dry and eventually open.
Christie Gross has been writing since 1998. Her work writing public policy platforms for elected officials nationwide has been featured in national and local newspapers under various client pen names. Gross has a Bachelor of Arts in English and political science, as well as a Master of Public Administration from the University of Delaware.