When do you use fertilisers?
If you keep the soil fertile by adding lots of bulky organic matter (well-rotted manure, compost, leaf mould) you shouldn’t have to worry about adding fertilisers. However, there are certain circumstances when it’s helpful:
- To raise nutrient levels in a poor or new soil.
- To get higher yields from hungry crops such as potatoes, cabbages & squashes.
- In containers where the nutrients in compost are used up quickly.
- Top dressings of fertiliser can be added once the plants have established.
- As an instant plant ‘pick-me-up’ sprayed on as foliar feeds.
Rich in potash (potassium or K – great for flowering), comfrey also contains high levels of Nitrogen (N) for leaves and Phosphorous (P) for roots. The variety Bocking 14 is the best one to plant as a fertiliser as it’s less invasive. Comfrey can be difficult to get hold of in Ireland and is usually obtained by asking fellow gardeners, though you may find it in local markets (I’ve been reliably informed there’s a market stall in Kilkenny Farmers Market that often sells it). The Organic Centre sometimes stock root cuttings and in the UK it’s available online from The Organic Gardening Catalogue.
Wilted Comfrey leaves can be placed around plants as a mulch or used as a liner in potato and tomato trenches. They can also be added to compost heaps (but only in small batches as they can go slimy). Be careful not to add any roots or flower heads or you may have comfrey popping up where you don’t want it.
A rich Comfrey brew is made by packing leaves into an old dustbin, about half way up, then placing a board on top, weighed down and a lid added. A hole can be drilled in the bottom of the bin and a jar placed under to catch the drips or a tap added. The resulting liquid should be diluted 10 – 20 times with water before use. Avoid getting it on your skin.
Nettles are high in nitrogen (so great for anything in the cabbage family). Young nettle leaves are cut in the spring (wearing a thick pair of gloves!) and made the same way as Comfrey tea. An easier method is to half fill a bucket with compacted nettles and cover with water. Use the liquid when it starts to smell.
Alternatively wrap some nettles up in a sheet of muslin or old net curtain, tie and hang in your water-butt. Change the bag frequently as the leaves break down so that the feed doesn’t become too strong.