Last January I had a dying rose. It only produced 2 new flowers. Now I currently have 2 bushes side by side with 11 dying flowers which are growing new buds out of them. One flower has a minimum of 9 new buds growing out of it. I've never seen this before. Is this common? The location is in Huntington Beach CA, close to the ocean, and nothing but yearly pruning is done.
Botanically, roses have 5 petals (but few with 4 petals).
Gardeners have selected and cultivated roses with mutations (stamens that become petals), and to build new cultivar, they selected roses that tend to mutate easily. These roses also don't produce fruits, so there is less adaptation and natural stability.
Thus it is not unexpected that roses could have additional defects, especially in the flowers.
This is a classic case of what's called proliferation - the cause is not fully known, but has been attributed to damage of some sort (like sudden frost), though there is no certainty regarding this anomaly other than its being down to disrupted DNA. It may occur on just one flower and never happen again, or on one or two flowers occasionally. I can certainly see what appear to be two normal flowers to the left of the second picture. However, if most of the bush does it all the time, then the likely cause is a virus and the plant should be removed and burned. More info below