Advice for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County
MGCC Help Desk Response: Thank you for contacting the UC Master Gardener Program Help Desk with your question about the change in the appearance of your rose blossoms.
The most common reason for a change in the appearance of rose blossoms is root stock take over, and we suspect this may be the case with your rose. It is not unusual for the rootstock rose to send up suckers and even take over the preferred rose.
Many roses are grafted. This means that a bud from a preferred species is grafted to the rootstock of a different species usually known for its vigor and longevity. Any shoots that grow from stems above the graft union will produce flowers from the preferred species. But any shoot that grows from stems or below the graft union will produce flowers from the rootstock. The two will usually differ in flowers and foliage form and color. You can trace the canes from the rootstock to their point of origination and remove them; otherwise, they will eventually replace the preferred species.
Here are some helpful links to UC information on rose care:
If rootstock takeover doesn't appear to be the cause of the change in your rose blossoms, please give us a call and let us know and we can discuss further.
Help Desk of the UC Master Gardener Program of Contra Costa County (SLH)
Note: UC Master Gardeners Program of Contra Costa's Help Desk is available almost year-round to answer your gardening questions. Except for a few holidays (e.g., last 2 weeks December), we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 2380 Bisso Lane, Concord, CA 94520. We can also be reached via telephone: (925) 608-6683, email: firstname.lastname@example.org, or on the web at http://ccmg.ucanr.edu/Ask_Us/. MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog.