Laying the foundation for the Autumn flush
Now is the time to prepare your roses for the autumn flush.
Rose growers all look forward to the autumn flush with great anticipation. This is when the softer coloured roses, especially the pale apricots and pearly pinks, come into their own. The cooler temperatures are kinder to them and the blooms also last longer. February is the month to lay the foundations for this autumn flush.
The heat in February can be a killer and the loss of water through transpiration is intense. Roses that are shooting and setting new buds draw up a lot of water and the quality of flush is definitely affected by too little water. Roses should be watered deeply at least twice a week and this can be increased to three times a week if there is no rain and temperatures remain consistently high.
If you have an automatic irrigation system, then set it so that the roses receive about 20 litres of water a week, delivered in small amounts on a daily basis, or every second or third day. Put a rain gauge in place and time how long it takes to reach the 15mm mark. If there is regular rain, bear in mind that 15mm represents one deep watering. Anything less than that means that you should still water your roses.
Overhead sprinkling or hosing down the leaves helps to cool down the environment around the roses and relieves some of the heat stress. With hot night time temperatures watering in the early evening will also cool down the garden and won’t encourage black spot because the leaves dry off quickly.
Monitor the roses at the edge of beds or on slight slopes to make sure that they are getting enough water and that it is not simply running off. Mulching is absolutely essential, not only to keep the roots cool and moist for longer but also to protect the beneficial soil life. Any kind of organic material can be used – I recently saw pine cones being used as very attractive mulch.
Your roses will also need a boost of Vigorosa or some other rose fertiliser but, if it is hot and dry, it is advisable to apply fertiliser only towards the end of February when the temperatures are usually lower. You don’t want to encourage new growth when it is very hot because this puts extra stress on a plant. Sprinkle the fertiliser evenly around the plant, watering it in well.
As per my advice in January, spray preventatively for black spot in rainy weather and monitor for red spider in hot, dry weather. Chronos, Rose Protector or Dithane can be used to control black spot. Use a sticker-like Spray Stay and combine it with Ludwig’s Insect Spray for added pest and powdery mildew control.
Light infestations of red spider can be controlled by using Ludwig’s Insect Spray, or hosing the underside of the leaves. Heavier infestations can be eradicated with Milbeknock followed, within a week, by Ludwig’s Spider Mite. If you applied Koinor as a drench at the beginning of the season it is now time for another application.
Remove all spent blooms regularly, disbud hybrid teas if you want good quality cutting blooms and remove the centre from candelabras.
Article by Ludwig Taschner