Q. Dear Peter, I like to mulch my rose bushes during those months that we have lower freezing temperatures, which our area is more prone to have. Is there any difference between using fir/pine needles and using deciduous leaves (usually ground up by my mower) to mulch tender plants? Betty Jones – Graham, WA
A. Most of the modern roses and grafted roses will appreciate some winter protection from our worst winter weather. They may make it through some mild winters but during our “zone defining” winters there can be some dieback on some varieties of roses. I have rugosa hybrids and an eglantine rose (old rose) that don’t require any winter protection. Our local rose society is a good knowledge base for what varieties grow well or need protection in our region (http://www.tacomarosesociety.org/). Consider attending one of their regular meetings. There are many materials that are recommended for protecting roses. These materials are usually mounded around the base to about a foot high to protect the graft union and the lower buds of the rose. The simplest and probably oldest method is to bring soil from another part of the garden and mound it around the base of the plants. I say from another section of the garden because you don’t want to pull up soil from around the plant itself since you will expose the feeder roots to winter damage. Wood chip mulch, manure, compost, sand, hay as well as leaves and needles have all been recommended at one time or another. The lighter of these measures will require chicken wire ring to keep them from blowing away. As far as I know there are no studies as to the thermal resistance value of these various methods but there are a few things to consider in your choice between leaves and needles. To prevent disease problems during the winter you need to keep excessive moisture away from the canes. Because of the amount of rain we get the chopped leaves have a better chance of matting down and becoming water logged. This means using well draining mulch. Therefore given the choice the needles may be superior. You can also get the benefits of both by mixing them up so that the needles keep the leaves from matting down and getting water logged.