Certified GKH Gardening Expert
The brown edges on the petals can be caused by a few different things. Sometimes it is just the age of the bloom and the edges of the petals will start to turn brown as the bloom ages and dies. If the blooms are new blooms, it could be a bit of light frost or cold damage if you have had some cold nights. The rose bush just cannot get enough moisture to the edges of the petals to protect them from being bitten by the cold and frost. It can also be caused by windy conditions that cause a bit of wind burn to the edges of the petals for the same lack of moisture to the delicate petal edges as mentioned previously. Also, if the temps have been very hot where you are, mid 90's to 100's, the petal edges can get a bit cooked. Again, this is due to the inability to get enough moisture to the edges of the delicate petals. Sometimes it can be caused by a fungus or insect problem, but these will usually show distress to more than just the petal edges, the entire bud or bloom will be affected. If the brown edges are a bit crispy, then the wind, heat or cold is usually the problem leading to the brown edges.