When finely ground and sterilised, bones provide a slowly available source of 'organic' phosphate, which is safe to handle. As a bonus, they also provide a useful level of slowly available 'organic' nitrogen.
Bonemeal is a particularly good pre-planting fertiliser for roses, shrubs, trees and other woody plants, encouraging strong and healthy root growth, leading to quick establishment. Vegetables, especially peas, potatoes, onions and root crops benefit from it and a regular dressing encourages the vigour and colour of outdoor bulbs and plants.
It may be applied all the year round as a base dressing before sowing and planting. Sprinkle it evenly over the whole area 140 grams per sq metre (4oz per square yard) and work into the top 10cm (4 inches) of soil with a fork. When planting roses, trees and shrubs, mix 140 grams (4oz) with the soil from the planting hole before planting. As a top dressing to established plants, sprinkle it evenly amongst bushes and flowers, between rows of vegetables or over the whole area covered by the branch spread of trees and shrubs. Hoe or rake in and, if dry, water well for maximum benefit.