Rose guru Ludwig Taschner’s inbox always overflows with gardening queries – and his answers could help you, too!
home August 2014
Q: My roses are still flowering – must I prune them?
A: The short answer is yes, but to understand why, here’s the explanation: Usually, frost in June causes the flowers and leaves to drop. But when this doesn’t happen, the roses keep on growing, especially if they’re being watered. However, roses are deciduous plants that react to short and long days. If the leaves that were produced during the short-day period didn’t drop off, when the days become longer, the plant gets the urge to produce new leaves and will ignore the older leaves. The old leaves are still producing sugar and carbohydrates, resulting in a concentration of these food sources which attracts spider mites.
The mites multiply exponentially and it doesn’t take long for them to invade the new long-day leaves. Such an invasion can hamper the bush for the rest of the season. Therefore, if you haven’t yet pruned your roses, do so now! Delaying for another week or two is not detrimental but will result in your roses flowering later than is usual.
Q: Last season, the new growth on my roses was often stunted and deformed and didn’t produce good flowers. What could have caused this?
A: It was very likely caused by thrips, which has become the biggest pest for roses. It won’t kill the roses but affects new growth and flowers. As larvae, thrips are almost invisible and that is when they do the damage, penetrating new growth and buds and sucking out the sap. By the time the damage is noticeable, it’s too late to do anything about it. Many gardeners say that once they’ve drenched the roses with Koinor (2ml per litre of water per rose), growth improves. It seems that there are organisms in the soil that inhibit root development and drenching with Koinor not only prevents aphids and sucking insects such as thrips on the new leaves, but also creates a more favourable balance in the soil. This is best done at the end of August when the roses are sprouting.
Q: Do all roses flower at the same time or can I plant varieties that flower at different times so that there are always blooms in my garden?
A: Indeed there are early-flowering varieties that flower one to two weeks earlier than most other varieties, such as ‘Duftwolke’, ‘Just Joey’, ‘Lyndal Dawn’ and ‘Pernille Poulsen’. Roses that flower a week or two later include ‘Deloitte & Touche’, ‘The Grannies’, ‘Bella Rosa’, ‘Yankee Doodle’ and ‘Flower Power’. However, this marked difference applies to the first flowering flush in spring only, and is balanced out with subsequent growing and flowering.