Monday, January 18, 2010
A critical date has passed in the pruning of my garden; one quarter of the time has elapsed, and only one eighth of the plants are now completed. Despite a push this week to reach the goal of 1000 pruned roses, just over 500 are finished.
Darrell spent a day with us on Thursday, and we made progress. As Darrell put it, 'I didn't realize that weeding would be involved as well.' The only thing I could think to say was that if I told everyone the naked truth, no one would come to help!
Teresa spent three days here this week, and worked with me yesterday all afternoon in the rain. An intense experience, as she put it! The Hybrid Teas and Floribundas are at least fairly easy to prune, but weeding as we go along has slowed the process. Soon we finish the modern HT beds and move to the old HTs where all of the weeding has been done, thanks to the Friends of Vintage Gardens. Most of those beds are now mulched with rice straw, as well.
True, we've begun with a very difficult section, the modern HT beds which were not pruned last year. And, that section, thanks to three years of heaping rich compost on the beds has become a haven for weeds, despite the three thorough weedings we did last year. Time for a less fertile mulch, for which I will forever be grateful to Michael and Pamela Temple who brought me 80 bales of rice straw. It turns to glue in the rain and seizes up like vegetable concrete when dry, so the weeds have little chance.
Rose Garden Cleanup
I've had some questions about other aspects of the winter cleanup process that need to be addressed. Perhaps the most critical is whether or not to do a dormant spray, and what to use. What we know about rose diseases and how they start up has improved in recent years through research at the University of California at Berkeley. It has long been believed that the spores of the fungi that afflict roses, Blackspot, Powdery Mildew, Rust and Downy Mildew, remain alive on the leaves that drop to the ground over the winter. Rose gardeners have long believed that even a fragment of a leaf can harbor these spores which, in proximity to the plants, cause rapid re-infection in the spring. NOT SO! The UC studies showed that leaves that are dead, no longer green, will carry few or no live fungal spores. This is excellent news, since it means that we can leave rose foliage on the ground to become a part of the soil, and feed soil organisms as they break down. Green foliage can still host live spores, but those leaves will die within some days of becoming detatched from the plants. A good way to insure their demise, and to keep the garden looking tidy after pruning, is to cover the ground with mulch of some sort, which will smother and kill of the remaining living cells in the leaves.
Spores will remain viable on leaves that are green and not stripped from the plant. This is why stripping off last year's leaves is so important to keeping the plants healthy. It's a tedious process, but one that is made less onerous by doing a light pruning. Cutting the plants back by 1/4 or so all over will remove the outer canopy which is where most foliage is found. Now here finally is a reason why pruning may make the plants healthier.
Some spores will also continue to live on the green stems of the plant. But fungal spores are everywhere in the air during the growing season, drifting onto rose plants and waiting for the ideal conditions of warmth, humidity and moderate night time temperatures. Dormant sprays may help to destroy hangers on, but will have little affect on spores that drift in during the growing season.
To Spray or Not to Spray...
I have practiced dormant spraying for many years, particularly on the crops of roses we sell at Vintage Gardens; these plants need to be completely free of disease as they ship out to customers. But, in recent years I have given up dormant spraying in my garden, as I find that the really critical time to prevent disease is after the growing season begins. That's when lots more fungal spores begin to drift in on the air.
Copper has been my preferred choice for a fungicide. It is widely used in the fruit tree industry, and like the other effective metallic sprays, Manganese and Zinc, can be applied in forms that are acceptable for organic farmers and gardeners. Liquid forms of copper for fruit tree application are widely available, but oddly enough, most garden centers and nurseries have never heard of using them on roses, and will often steer you away from them and toward the non-organic fungicides which are more toxic. All three of these metals have been used in various fomulations of fungicides, and I have employed them all.
Blackspot and Powdery Mildew are easy to prevent with copper sprays. Downy Mildew can be controlled as well, but in Coastal California, where conditions can be ideal for the spread of this sometimes virulent disease, repeated applications may be necessary, particularly during the growing period in the spring in advance of the bloom.
Rust is another matter. I have found Zinc and Manganese to be tolerable successful if used before signs of the disease appear. But these are not easy to obtain, and not 100% effective. In our coastal climate Rust is a big problem. It can be best controlled in my opinion by stripping affected leaves during the bloom season. However, one easy way to avoid it altogether is to be ruthless in removing varieties of roses that seem particularly susceptible. Peace is an excellent example of a Rust lover. In general, Hybrid Teas are much more prone to rust, along with their 19th century parents, the Hybrid Perpetuals. Bourbon roses get it as well, though not all. It is in the Teas and Chinas that we find prolific, year-round bloomers that seem not at all sensitive to Rust. If you're faced with a plague of Rust, rethink your garden, and start growing these delightful groups of roses that may solve the problem. I once believed, as many do, that Rugosa roses were completely disease free, and indeed they may be. However I've found that they can be completely defoilated by Rust near the coast. I continue to grow and love them, but understand that some years I may be in for a clash of orange and magenta where I have them planted!
What to Use and How Much?
Inevitably I am asked which sprays to use and how much. Beyond my favoring the metallic sprays, I give no advice. What is available to you, where you live, what diseases tend to be your bugaboos, which product you are using, involved variables that to advise with good judgement would take research and consultation that I have not enough time to pursue. Vendors of dormant sprays should be able to advise you, or they should not be selling the stuff. Sadly, there is too little knowledge to be found in most markets that sell chemicals. And, much of it is out of date or too limited. One thing to keep in mind is that copper can be used throughout the growing season. Sales people will contradict this, but you need only read the instructions on a bottle of liquid copper to see that it can be used during the growing season even on delicate leafy vegetables. The key thing to look at is concentrations that are given for various stages in the growing year.
If you want my real opinion, that's it. Get rid of roses that are prone to disease in your climate; replace them with types that will be less disease prone. Strip the leaves from the plants in the winter. Strip diseased leaves during the growing season.
Ever Green—What This Blog's All About
I'm often asked for reccommendations for roses that are evergreen. Knowing how prone hybrid roses are to various diseases, I wonder why this is desirable? There are plenty of good evergreen plants for every climate that are tough and disease free, and roses don't need to be among them. However Teas and Chinas will tend to be evergreen in mild-winter climates, and these may indeed be worthy of trying. In California, where Rust can be problematic, the Teas and Chinas may afford the best choices. In my own climate, where frost and even freezing occurs every year, the Teas and Chinas shed their leaves to a great extent; usually leaving only a light outer canopy of new foliage which can be quickly sheered off to eliminate the chance of the spread of fungi from one year to the next.