Cultivated soils, particularly in old gardens frequently suffer from compaction, bad drainage, broken and fragmented structure and devoid of organic matter, usually through bad management in the past, these conditions are incapable of supporting a population of worms, therefore before worms are introduced, these conditions must be remedied. Once this has been achieved, a population of worms can be introduced.
There are two species of soil dwelling worm currently available, these are Lumbricus terrestris and Eisenia hortensis.
Lumbricus terrestris is the large worm that most people are familiar with, it is a slow breeding worm that likes to live in deep undisturbed soils, it also throws worm casts onto the surface and can be seen on grass, particularly after warm rain at night, giving it one of its common names of “Dew worm”
This worm should only be introduced into areas where it will not be disturbed on a regular basis and where the casts on the surface will not cause a problem, many of these worms are deliberately killed because of the “problem” of casts on the lawn.
Eisenia hortensis in contrast, is a comparatively rapid breeder, lives in the top 12 inches of soil and does not throw casts to the surface, making it a good choice for lawn areas, areas likely to be disturbed and areas where the soil is not very deep.
Both species will need ongoing feed in the form of organic matter either as a mulch or not collecting the grass clippings once in a while.
Both worms are a good source of food for wildlife and can be most beneficial in this way.
Once the worms have been introduced, the use of herbicides and pesticides should not be carried out for at least 12 months and preferably not at all.
Any worms purchased to be introduced into the soil should never be just scattered on the surface in the belief they will burrow down – they won’t! If left on the surface they are likely to be picked off by the local bird population or even killed off by the sun and ultra violet light.
With both species they should be “planted” dig trowel depth holes, a couple every square metre, water the hole, put in a little natural compost, NOT potting compost, add a few worms and break up the removed soil and put back on top.
In new areas used for shrubs etc, this should be done before any mulch is spread and in lawn areas, before turf or seed are laid, if worms are being introduced to an established garden then there is no choice but to dig the holes through the mulch or grass. The quantity of worms per hole is really down to the customer but as a guide, 2 or 3 Lumbricus terrestris and with Eisenia hortensis, a very small handful or a very large pinch!
What quantity should be planted?
The quantity of worms required is not an exact science, as a rough guide you should be aiming for the following:
Eisenia hortensis – up to 20 worms per square metre, this can be increased or decreased according to budget but not by more than +50% or -50%.
Lumbricus terrestris – this would be around 5 worms per square metre minimum but again the same rule applies as above.
The quantities are governed by surface area NOT depth.
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