Does anybody know why the edges of the bloom will always turn black and then brown. Here is a link to a photo
Thank you.
What is the variety? That looks like sunburn, but have you checked inside the bud for thrip?
Dave, there are many answers to that question, and some of them may or may not apply to the particular rose in question. Taboo did that religiously here in Southern California. With some, it is likely genetic. Extreme heat or intense sun combined with dark color can lead to excessive heat build-up at the petal tips where the tissue is smaller, thinner, causing it to burn. Softer petals can also be more easily heat damaged.
Water stress can cause similar petal damage. Though the plant is sitting in water, if prevailing conditions cause it to transpire more water, faster, than it can take up, temporary water stress can result and the more tender parts of the blooms can burn. Excessive salt levels in the soil can draw water out of the plant resulting in flower and leaf burn. As that increases to dangerous levels, soft new tips can be dried out. You will often see that occur after fertilizing. If the soil and plant don’t have sufficient water in them and fertilizer is applied, you’re basically watering the plant with salty water and drawing more water out of the plant than putting in it.
I’d imagine, all else being equal, the petal tip burn you’re describing is more likely on darker varieties exposed to hotter sun for longer periods. You will probably see it worst on those whose petals try to point and reflex, creating a spot of intensified heat. The easiest ‘cure’ is to either avoid the darker colors and those whose petals take on that formation, or plant them where they will receive shade or filtered light during the hottest part of the day. If there is some way to provide that shade at those times, it may work. I knew an avid exhibitor here in Southern California who used to have dozens of the portable gazebos she would erect and move around her garden just for that purpose to insure she would have perfect blooms for rose shows.
The photo you posted shows the darkening at the petal points. If it happens along the margins of them, it’s more likely due to water stress/salt build-up, excessive heat from temperatures or brilliant sun, or too soft petal textures for the conditions and culture they endure. Kim
Its Black Magic. Its especially common in reds with excess pelargonidin, and those specific red types can produce russet and orange-red more easily. Likewise, the older roses heavy in cyanin, usually those with the heavy damask scent, tend to also do this. Its the reds that that are more even-toned or heavy in peonin that tend to stray from this trait. The trait itself can be a blessing or a blemish, depending upon circumstance and/or variety specifics. You will note that even Playboy will open up with little black tips in cooler weather. Its not from scorch, in this example. My rose bred from Playboy, Shadow Ninja, will get black edges in hot, humid weather. It is also not scorch. Food for thought…