Fertiliser can be expensive. It can be time-consuming to apply. It can also use valuable resources and even contribute to environmental pollution. So here’s some great news: in many cases, slavish devotion to its application is not only unnecessary, but cutting down on its use can give you far better results. You just need to know how to feed wisely.
Plants are truly amazing, in that, unlike animals, they can simply manufacture their own food. Functioning as living solar panels, they trap the energy from solar radiation and convert it into the sugars that fuel their growth via the miracle of photosynthesis. However, while plants can indeed create their own food, they do require small amounts of certain minerals to make their cells and the chemicals they contain. In most plants these are accessed by simply pumping them out of the soil (basically a mix of minerals, water, air and microbial life) via the action of their roots. They do this all the time when in active growth, without any need for human intervention.
Their requirement for additional fertiliser applications only comes into play when the growing media their roots are in is deficient in these key minerals. In fact, paradoxically, over-feeding can not only result in soft, sappy plant growth that is more vulnerable to environmental stresses, such as drought, cold, heat and pest attack, but can also cause the pollution of water courses. Yes, even the organic feeds.
Fortunately, UK garden soils tend to be far richer than agricultural soils, so if you maintain good soil health, for many plants extra additions of fertiliser are not strictly necessary. This is particularly the case for large, established plants, such as shrubs and trees, as well as most hardy perennials. The easiest way to maintain good soil health is by regular applications of organic matter to boost populations of friendly soil micro-organisms and replace any minerals lost from the system by harvesting and pruning. This can be done by simply adding a 10cm layer of homemade compost over the surface of the ground every autumn.
However, if the growing media a plant’s roots are in is naturally low in these essential minerals, such as many peat or plant-fibre-based blends, they will indeed require additional applications to top-up these levels. This is particularly the case for quick-growing plants in small containers of such compost, so pretty much any bedding species or annual vegetables in window boxes, patio pots and hanging baskets.
One solution that may help is to use a soil-based potting mix, such as John Innes, which will contain a far higher mineral content, and thus need less frequent topping up. Much like vitamin supplements in people, applying fertiliser correctly can transform the growth of plants suffering from a deficiency, but if they already have access to all they need, additions are at best unnecessary, at worst potentially problematic. So feed wisely to save yourself time and money, and potentially get better results for your plot and the planet.