I do not understand why many of my rosebushes are losing their leaves. I have a lot of totally bare canes!
When I try to figure out the cause of leaf loss in any shrub, I try and go through the following possibilities: 1. Is it going into dormancy? Obviously not in the case of your roses, given where you are and the time of the year it is. 2. Is there a nutrient deficiency? Probably not. It would be unusual to get leaf drop without other pretty obvious signs of deficiency - poor growth, poor blooming, yellowing, etc. 3. What about pests, bugs and animals? Pests and bugs that eat the leaves should leave tell tale signs. But spider mites can be difficult to identify to the unsuspecting gardener. Again, there well be signs that things are not right - the leaves yellow, and appear dry before they fall off. If you look at the underside of the leaves, there will be what appears to be a "spider web" type material, except that the strains are much finer. You may even see the mites crawling about. And certain types of pets may make a habit of micturating around certain specific bushes to "mark" their territories. If this only happers occassionally, it may do no harm. But if it's a frequent occurrence, especially if accompanied with stresses of relative water shortage, it may be a problem. 4. Then there are the diseases. The most troublesome ones for roses are black spots and mildew. Black spots are obvious - it declares itself with those black roundish spots on the leaves. The leaves then turn yellow and fall off. But black spots tend to be a progressive disease. Initially a few leaves will be affected. Then, through cycles of rain and wetness, the spores of the initial lesions spread to adjoining leaves. Mildew is seen as a powdery residual or coating on the leaves. The powdery type is worse in dry conditions. 5. Watering - too much or too little. Roses love water, but not too much. Too much water drowns the plants - depriving the roots of oxygen. And increasing the risk of rot. Too little water causes severe stress and force the plants into dormancy by dropping it's leaves. Worse, the roots could dry up completely and the roses would die. You can easily figure out if this is a problem, if you dig a little test hole near the root ball of your roses - if water droplets can be squeezed out of the soil, it's too wet. It would be very obvious it it's too dry. You might as well fill the hole up completely with water and time how long it takes for the water to drain away completely. That way, you can also figure out what the underlying drainage problem is - too slow or too fast. An alternative is to invest in a moisture meter - those are actually quick cheap, less than $10 usually. 6. If all those seem to be in order - then I start to wonder if the problem is "iatrogenic". I.e., the result of something that I have done, albeit with good intentions. Have I used any herbicides in the vicinity of the shrubs recently? Or has my neighbour used it and potentially caused an overspray of the chemical? Did I go overboard with all that fertiliser? I am not sure if any of the above will provide you with an answer. But it should give you enough investigative work to fill up a chapter or two of a Sherlock Holme mystery novel. My take is that if I don't find any answer after exploring all of the above, then, it's on to the post mortem - i.e. shovel prune those roses.
Thank you Ron: I shall investigate options 3, 4, and 5 tomorrow. The roses have bloomed beautifully. Yet, as I said, I have great amounts of bare cane among most of the ones planted in the ground. The ones planted in the 1/2 wine barrels are fine. It must be the watering. I will look into it. Holly
