By mid-August you should be almost done with your rose pruning. Don't worry if you haven't quite gotten there. One very wet year, I finally managed to finish my pruning in September – not ideal but the roses still bloomed in November. In fact you could not tell the difference between the ones pruned in June and those in September!
This column I will talk a bit about fertilising roses and what you need to do to have great roses. Fertilising roses is like pruning, it needs to be done to get the best results but if you are a week or two late, it is not the end of the world. There is also a lot of information out there so I want to present a straightforward guide to fertilising roses.
First, why do we need to fertilise roses?
Easy, because a well fed rose is a healthy rose and will perform much better than one that is hungry. A bit like humans really in that if we are hungry, we are more susceptible to diseases.
There is a huge array of fertilisers on the market for a wide range of plants including roses. Almost all with have the letters NPK on the bag with numbers beside them. NPK stands for (N) Nitrogen, (P) Phosphorus, and (K) Potassium and is the percentage of the element in the fertiliser. Nitrogen promotes vegetative growth in plants, Phosphorus promotes root and shoot growth and Potassium promotes fruit and flowering in plants.
There are also other elements in fertilisers like sulphur, manganese, calcium, boron and iron. All are required for good growth and flowering even if in very small quantities. Knowing what NPK stands for will help when reading bags of fertiliser as you can decide which is best for your garden. Generally anything for flowering plants will be suitable to fertiliser your roses with – there are even branded rose fertilisers available.
First Application on the Roses
In late August and into September, you want to get your first application on as the roses are coming into growth. Read the application rates on whatever you use and always apply fertiliser to damp soils, scattering around the plants and then hoeing in lightly. If applying fertilisers when the soil is dry, you can end up with the fertiliser burning the roots and the plants will sulk.
You then want to do similar applications in December after the first flush of blooms and again no later than the end of February. After this time, let the roses prepare for winter and the canes harden up. Sometimes fertiliser is applied with a summer trim when the roses are cut back, fed and watered to get them coming away into flower. This often done after the Christmas holiday season when our roses are not always looked after. I'll cover summer trimming in another column.
Checking the Soil
In April, you may want to check the pH of your soil. pH is the measure of acidity and for roses, they like a slightly acidic soil of around 6 on the scale. Remember 1 is acid and 14 is alkaline. Use lime to raise the pH of soils, dolomite lime is good as it works faster.
When planting roses, you can use a bit of blood and bone in the hole but nothing else. Anything strong will burn the new roots. You can also put some blood and bone around the plants at pruning time.
Happy fertilising!