The array of fertilizers available at your local garden center can be a little confusing. So if you have no clue as to what's best for your own particular situation, you might end up choosing either the wrong solution... or paying far too much for a "specialist" type. So let's sort out what you (and your roses)actually need.
All fertilizers will show the ratio of these 3 important elements. N stands for Nitrogen, and this is what helps a plant grow big healthy foliage. P stands for Phospherus, and this element is used by plants to strengthen their root system, which helps with higher crop yields (and more flowers!). And finally, K, which is Potassium. This helps a plant maintain oveall health and vigor. Plants that are lacking in Potassium will be smaller and produce less.
Knowing this, it makes sense that a fertilizer with a ratio of N:12 P:4 K:4 will be great for "leafy" type crops (perhaps cabbage, cauliflower etc). And another fertilizer with the ratio of N:4 P:12 K:4 is going to benefit crops that rely more on their root system. Potatoes for example.
Do You Need Specialist Fertilizers?
You will see many different variations on this in your garden center. Fertilizers that claim to be specially formulated for roses, camellias, vegetables, tomatoes etc etc. And to be honest, this is really nothing more than a way to increase the price dramatically, they are what you would call VAP or Value Added Products. Slap a label on them to say they are for Tomatoes, put them into a smaller container, and double the price. Buit don't be fooled into thinking you have to get these.
All you need to do is check the label to see what elements they have increased, and match that as closely as you can with any of the cheaper more generalized fertilizers, and perhaps do a little "mix and matching" of your own.
For example, most fertilizers that are specifically for flowering planst such as roses, have a higher concentration of the N and P, and less of the K, compared to a more balanced general fertilizer. But if you wanted to increase those elements, then Potash is very high in P (wood ash will give you plenty of this!) and Blood and Bone is high in N and P.
As a price comparison, I looked at Yates Blood and Bone, which worked out at $2.60 per KG. Compare that to Neutrog "Sudden Impact for Roses" which is $4.40 per KG and even more if you buy less than a 10kg pail. Yet both of these are roughly equivalent. So for me, I would be using Blood and Bone, with perhaps a top up of general purpose fertilizer and/or compost at the start of the flowering season.
There is nothing more satisfying than creating your own compost. And, it is every bit as good as any commercially bought fertilizer. Better in fact, as it also adds much more than the basic nutrients to your soil. This is black gold, and when we moved into our new house last year, I even went to the trouble of bagging up as much of my compost as I could to bring with me. The bags were heavy but worth it to me, as creating more compost is going to take 6 months.
If I think back to my first compost heaps, they were total failures. Either they dried out and didn't rot down, or they got waterlogged and slimy. It seemed I could never find that balance. Turns out, I had three main problems.
1. I wasn't keeping the material at the correct moisture content
2. My heap wasn't big enough to generate the required heat.
3. I had no idea that I was meant to layer different types of waste.
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