I have a rose bush that is sickly, but the one next to it is ok. What should I do? Mara C.
Denver County Colorado roses
The brown and crispy outer edges of those leaves suggest your rose may be suffering from a "scorch" issue. It has been very hot since early July and your roses look like they front a brick wall which gives off reflected heat and makes for a particularly hot microclimate. That rose might not be getting enough water to compensate. It's possible there is just enough site difference between the two plants to account for the difference in color and leaves, but it's more likely that there is something about the watering or soil that explains the difference. You'll have do some investigation.
Before and after you water, stick a probe (like a screwdriver) into the soil around the base of the roses and get a sense of soil moisture. Is it the same for both roses? Does it percolate down or does it pool up? Pull the mulch back, so you can get a good look.
If the water behaves differently, hunt for causes: is an irrigation head delivering different amounts of water because of water is blocked by another plant, or a head is mis-aligned, or because the spray nozzle is clogged? Put out low containers (like tuna fish cans) by each rose and measure the water in each. Is it the same?
If all the irrigation is in good order, and you are providing about an inch and half or so per week in high summer, you could consider whether the soil might be too wet around that rose. Plants - particularly those growing in clay soil - can suffer from too much water as well as too little so it's possible, although less likely, that the scorch is because of too much water or there's some problem with drainage (is there a downspout nearby? does that rose get overspray from another irrigation head? etc.)
If you haven't been regularly fertilizing your rose, you might try giving that rose a hit of fertilizer at half-strength to see if it greens up. September normally is the time you want to start encouraging plants to go dormant in preparation for cold weather events, but in this case it might be useful to know whether the light green color on that rose is due to a nutrient deficiency. If the plant greens up following an application of general purpose fertilizer, you'll know next year to provide a little more fertilizer than you did this year.