Q: In February, I always spray my roses with oil and lime sulphur mix, but my Westerland roses are still covered with glossy green leaves and new shoots. Do I spray anyway? Also, tradition says that roses get pruned when the forsythia blossoms, but the Westerlands are already growing. Can I prune now?
Ariel Bowers
A: Westerland roses are reputed to be extremely disease-resistant and I question whether the lime sulphur-dormant oil is really necessary for them. It's significant that after a year of growth and a nasty cold snap the leaves are still glossy green.
Lime sulphur can burn rose leaves, but leaf burn is unlikely to kill rose bushes. Still, the new shoots may be susceptible. If they do get burnt, you'll probably get some dieback and growth will stop until the dormant buds lower down the stem begin to shoot.
If the rose were mine, I'd probably neglect the spraying for this year. It would be a learning experience to wait, watch and see what happens. You may find your Westerland roses have a good, natural fungal resistance, which operates with no help from you.
As for the pruning, you can go ahead with it immediately. These are vigorous roses and will bounce back quickly.
The rationale behind waiting to prune roses till the buds swell and the advice about lime sulphur burns is based on the behaviour of roses in the past.
Severe winter cold can cause dieback on roses. If they've already been pruned, the dieback is likely to attack further into the bush.
The warning about lime sulphur applies to most, if not all, older rose varieties that have much thinner leaves than the new generations of disease-resistant roses.
Q: I recently noticed that the large azalea bush at the front of our apartment building has green moss growing on it branches. My potted Japanese maple tree on my balcony has the same problem. Any suggestions?
Carol Moon
A: Moss doesn't actually kill the branches it grows on - it just uses them as a holdfast while it carries on photosynthesis and absorbs moisture from rain and the air.
But because it does best in places where there's little air movement, moss tends to grow where branches are overcrowded. Moss also favours older branches that are starting to die back.
Pruning some older, mossy branches away will encourage the growth of vigorous new branches and let light and air circulation into the bush.
You might remove some of the moss by hand from your maple tree. It shouldn't be difficult since the tree is fairly small. But because moss spores drift around on the air, the moss will re-grow every winter. That's just part of rainforest living.
Q: I have a Wisley Blue clematis in a pot with a small trellis. Should I prune it now, and, if so, how much should I cut off? It looks quite unruly."
Valerie Ahwee
A: This is the perfect time to prune your Wisley Blue.
Just cut all the top growth down to 30 to 45 centimetres above ground level to strong buds. New, strong growth will be quick to emerge. If any old, dead leaves are still hanging about, they should be removed and composted.
Anne Marrison is happy to answer garden questions. Send them to [email protected].
