March is the best time to feed trees, shrubs and hedges with a balanced fertiliser (such as growmore or blood, fish and bone). This is because your trees and shrubs will be emerging from their winter dormant period.
Fertilisers are a concentrated source of plant nutrients in chemical or organic form. Some also contain trace elements, which plants only need in tiny amounts.
Most fertilisers are based on the three major plant nutrients:
Nitrogen (N): For green leafy growth
Phosphorus (P): For healthy root and shoot growth
Potassium (K): For flowering, fruiting and general hardiness
If you look on any packet of fertiliser they should quote their N:P:K ratio. For example, a ratio of 7:7:7 indicates a balanced fertiliser (Vitax Growmore), but a ratio of 5:5:10 would indicate a high potassium fertiliser (in this case Vitax Rose Food).
Fertilisers will either be organic (derived from plant or animal) or inorganic (man-made).
Organic fertilisers: contain plant nutrients in organic form. They tend to be slower acting, as large organic molecules have to be broken down by soil organisms before the nutrients within them are released for plant use. However, organic fertilisers are a “traditional” choice and whilst they have been used for hundreds of years they still remain popular due to their results. Dried blood, fish blood & bone, seaweed extract, bone meal and poultry manure pellets are all example of this type of fertiliser.
Inorganic fertilisers: are synthetic, artificial forms of plant nutrients. They are usually more concentrated and faster acting than organic fertilisers. Examples include modern brands such as Miracle-Gro, Phostrogen, Tomorite as well as Growmore, Sulphate of Ammonia, Sulphate of Potash and Superphosphate
Within each category (organic or inorganic) there are further options…
Slow release fertilisers: These degrade slowly, usually under the influence of soil micro-organisms to release their nutrients. These are best used when the soil is warm as that will speed up the leaching of the nutrients into the soil. An example is bone meal.
Compound fertilisers: These contain a mixture of different nutrients, and may be balanced (containing similar proportions of all the major plant nutrients) or may supply more of some nutrients than others, as per the requirements of different crops. They may be organic or inorganic, or contain both. Most fertilisers labelled ‘all purpose’ will be a compound fertiliser.
Straight fertilisers: These contain only one or mainly one nutrient. They are usually used to provide different nutrients at different times of the year, or to correct particular nutrient deficiency. You can find these altogether in our specialist fertiliser area.
Controlled release fertilisers: These are almost always granules of inorganic fertilisers coated with a porous material such as sulphur or synthetic resin. Water enters the granule and the fertilisers leach out into the surrounding soil. The warmer the soil, the faster the leaching; this corresponds to plant growth which is faster in warm weather. By varying the thickness of the coating granules can be designed to feed plants for different periods of time. These are useful in baskets and containers where the access to soil nutrients is limited to that basket volume of compost.
Always read the label of any fertiliser before you use it and wear gardening gloves if you intend to handle it. Follow the directions on the packet but assuming you go for grow more or blood, fish and bone we recommend you sprinkle the fertiliser over the root area before hoeing it into the top layer of the soil surface. This will particularly benefit young, weak, damaged or heavily pruned plants.
For help selecting the right fertiliser for your plants just ask one of our team when you next visit us.