Winter pruning stimulates root activity and sprouting of dormant eyes. The speed of development is partially dependent on temperature, but also on the water and nutrients available. It is obvious that watering and feeding should commence fairly soon after pruning has been completed.
- Water the bed or soil around the rose bushes thoroughly, especially if watering has been applied sparingly over the past weeks during dormancy.
- Check the soil condition in the rose bed by digging with a garden fork and getting a feel of the soil structure at root level. The soil should crumble in your hand. If it is hard and lumpy, air and water have difficulty penetrating down to the roots, resulting in poor root development. Poor soil condition is remedied by introducing organic material such as compost, old manure, peanut shells, and milled pine bark, even partially decomposed leaves and lawn clippings. Mix this material with the soil by digging it over to the depth of the fork tines. Try not to loosen strong roots: reposition the fork if it meets resistance from roots.
Be careful not to raise the soil level in a rose bed year after year by introducing compost and mulch. This can cause the root system eventually to be settled too deeply, where the soil remains too cold and wet for the development of micro-organisms.
The roots of roses should be encouraged to grow downwards and to find the best level for developing a fine hair root system. This is the best time of year to help establish such growth habits. Digging out a plant that has performed poorly can show whether it has been too deeply covered. If so, there are two ways of addressing the problem. Either simply remove most of the composted top layer in the rose bed down to the correct level – where the bud union or knob is just covered with soil – and then loosen the topsoil, so that remaining compost can penetrate down to the deeper level where the main roots are embedded. If insufficient composted soil remains at this level, remove a further layer of about 10 cm, restore some of the compost, and proceed to dig it in. Alternatively, dig up the rose bush, cut away roots that have formed higher up and above the bud union and replant the rose after having dug over the bed and mixed the good topsoil with some of the subsoil.
- The first fertilizing of the season is carried out soon after pruning. If organics are also being dug into the soil, it is easier to spread both fertilizer and organics over the soil surface and to dig them in together. If, however, the existing mulch has decomposed and now consists of a thin layer of compost, spread just the fertilizer over the old mulch and mix together with the top 10 cm of soil. See here for the recommended fertilizing procedure.
- Water well again after having dug over the soil. Any loosened roots must be well embedded in the soil, and this can only be achieved with heavy watering. See watering instructions
- Spray with lime sulphur, Ludwig’s Insect Spray or Oleum, although this is not essential if you have adhered to a regular spraying programme throughout the season. One part of lime sulphur is diluted with five parts of water. If pernicious scale is present on the lower parts of the stems, mix 100 ml of Ludwig’s Insect Spray or Oleum in 10 litres of water and add 10 ml of Metasystox or Ripcord for best results.
- The rose or stalk borer wasp seems to smell open cut wounds, and if they are in the vicinity they awaken and will drill down the soft pith found in the centre of a rose stem. Such holes are not detrimental or cause die back and if you have sprayed diligently with an insecticide during the season, the borer will likely have been eradicated from the garden. If not, it is best to seal all cuts with Steriseal, ordinary PVC paint or with a little clay.
- Mulch keeps the soil cool and retains moisture, but a thick application early in the season when temperatures are still low actually prevents the soil from warming up. It is better to start a fresh layer of mulch towards the end of August.
- From now on, water the rose bed weekly, increasing to twice weekly once the roses show rapid growth and temperatures have increased.
- Pest control of roses becomes necessary in early September in all regions.