Sitting in a traffic jam yesterday, I spied a rather elegant window box through the car window, and I was there long enough for some deeper thought. I took out my trusty mobile and captured the scene.
I liked the combination of white shuttered window with the black planter. I also liked the contrast of the attractively marked pelargonium leaves with the bright scarlet flower heads – but I knew that there could have been more.
For a plant to flower its little head off, it must have access to the right kind of plant food, and here the right kind of fertiliser balance is less nitrogen and more potassium.
Not all plant foods are the same, and the NPK ratio is written on the side of the pack. The NPK ratio of the one that I always recommend for a flowering plant is 12:7:19 which is perfect.
However, the one concern than I did have while I sat there in the traffic queue was that the planted (presumably metal) was sitting straight onto the concrete windowsill.
This is not a good idea for a couple of reasons.
The main one is that as the sun shines on the windowsill, it will heat up and this heat is then radiated upwards (like a night storage heater) through the pot. The net result is that the soil dries out very quickly and the roots could ‘cook’. Actually, the same temperature transfer happens in winter, but this time it’s a chill that’s travelling; and cold roots are not happy roots, believe me!
The remedy is to create an air barrier between the bottom of the pot and the stone windowsill and this breaks the transfer of heat/cold very nicely.
Garden centres do sell pot feet, but if these are not your bag, then you can simply elevate your container by using short wooden dowels that you can slot in at each end of the pot. If you cut them carefully and paint them black, then they will remain relatively hidden.
A word of caution, make sure that in doing this you don’t block up any drainage holes as this will create another folly.
At that point, the traffic moved.
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