Quick facts
A plant does not eat compost. It takes up dissolved ions through its roots. So why not supply those directly and skip the middleman?
Because the middleman does most of the work. Soil organisms — bacteria, fungi, springtails, worms — break organic matter down slowly, and in doing so glue mineral particles into crumbs. Those crumbs create the pore spaces that let water drain and air reach the roots. Mycorrhizal fungi extend a plant's effective root system many times over in exchange for sugars. None of that happens in soil fed only from a bag.
Feed a plant and you get a season. Feed a soil and you get a garden.
The practical version: get organic matter onto your soil every year, in whatever form you can get, and stop damaging the structure you are building.
The cheapest and best source, made from your own waste. Keep a rough balance of greens (grass clippings, kitchen waste, soft prunings) and browns (cardboard, autumn leaves, straw), moist but covered, and turn it occasionally for air. Here the usual fault is too wet and too airless — add more cardboard than you think you need. Expect nine to eighteen months in a cool heap.
Horse, cattle or poultry manure stacked at least a year, until dark, crumbly and inoffensive. Higher in nutrients than compost and excellent on vegetable ground and hungry shrubs. Ask what the pasture was treated with — persistent herbicide residues survive composting and distort beans, potatoes and tomatoes.
Autumn leaves stacked in a wire cage, or bagged with a few holes punched in, and left two years. Fungi rather than bacteria do this work, so it is slow and cool. Low in nutrients but superb structure, and the natural match for woodland plants.
Crops grown to be cut down and left. On empty vegetable ground over winter, field beans (Vicia faba) and winter rye (Secale cereale) hold nutrients that would otherwise leach away in the rain, and their roots keep the structure open. Phacelia tanacetifolia is fast, easy and good for bees if you let some flower. Cut them before they seed and leave the residue on the surface.
A soil conditioner — compost, manure, leafmould — improves structure, water-holding and biology, and supplies nutrients slowly. A fertiliser supplies concentrated nutrients and does nothing for structure. Borders that receive organic matter annually rarely need one.
The three numbers on a fertiliser bag are the percentages of nitrogen, phosphorus and potassium.
A fertiliser is warranted in four situations:
Use a balanced general fertiliser such as blood, fish and bone in spring, a high-potash feed for flowering and fruiting, and stop there. Excess nitrogen produces soft growth that wind burns and aphids find first.
Digging inverts the soil profile, breaks up fungal networks, burns off organic matter and brings a fresh batch of weed seed to the light. No-dig stops doing it: clear the weeds, lay compost on the surface, and plant into that. Worms do the incorporation, and weeding drops sharply after the first year.
The enemy it really addresses is compaction. Compacted soil has no pore space, so it neither drains nor holds air, and roots stop at the pan. On wet Irish clay it is easy to cause and slow to undo. Permanent beds no wider than you can reach across, boards when you must work in winter, and a rule against walking on cultivated ground will do more than any product.
Common mistakes
If you would like a second opinion on a border that has never performed, our team is happy to look at photographs when you call into the nursery.
First and foremost, you will need to consider the quantity of plants required to achieve a full looking hedge. We usually recommend 2.5 plants per linear metre for a fully mature hedge. For a semi mature hedge, you can plant 2 plants per metre.
However, different types of hedging plants have different growth habits, so the quantities of plants you may need could vary. it is always best to check with your local nursery.
