Winter and Roses - - A Time to Rest
by Jolene Adams, Roses Chair
Winter is the time that roses rest. Or, they are supposed to! In California, many of our microclimates are too warm for dormancy – not enough chill hours to force the roses to stop growing and blooming.
All deciduous trees and shrubs are dropping leaves now – your modern roses should too. But many of us will need to force them to defoliate and go to sleep by spraying a copper and sulfur oil spray (dormant spray) on them to help leaf drop occur.
The dormant spray is also good for eliminating spores from rose diseases and smothering insect eggs that are hidden in the cracks and crevices of the bark on the rose stems. Sulfur is a necessary ingredient in rose nutrition so don’t worry about using too much – spray the whole bush, tops and undersides of leaves, stems and base, until the spray drips off. You can also mist the ground around the rose.
Sanitation in the rose bed is important in winter – our rainy season. Dead leaves and petals lying on the damp soil will harbor molds and mildews that attack roses, and give refuge to the eggs and larvae of many insects. Beneficial insects don’t overwinter on roses, so what is left are the “not good guys”.
Late winter is pruning time – a necessary step in good gardening with modern roses. They need to have a lot of the old growth trimmed back, spindly growth removed, older canes cut off at the base so that the stored food in the root system can start new growth in the Spring.
Cutting limbs off trees and shrubs stimulates new growth - so prune after the last possible hint of freezing temps - or in January for coastal and lowland gardeners.
When pruning, remove the top growth by at least half – more if the rose is a robust grower. Strip off any remaining leaves. Old canes will have greyish bark, newer canes will have green skin - not bark. You want to remove the old ones and save big, juicy new ones.
Look closely at the stem - find a leaf scar (like a smiley face) on the outside face of the cane, and cut at an angle. Make sure the high side of the cut is on the outside. Slanted cuts like this also help reduce fungal infections by forcing moisture to roll off the cut surface.
After pruning, spray once more with a calcium polysulfide solution (another dormant spray - smells like rotten eggs) to coat the remaining stems.
Remember - Stop, and Smell the Roses!