Plants such as sweet peas or Liliums require significant depth for their roots and the best way to achieve this is by bastard trenching:
- Mark out the area required with string and divide it into strips about one metre wide.
- In a trench about 300mm across, remove topsoil to a depth of about 250mm and pile it to one side of the bed.
- Dig over the bottom soil, breaking it up and adding organic matter such as well-rotted kraal manure or compost, together with a handful of bone meal per running metre.
- When this section of trench is totally dug over, move your line another 300mm and dig a second trench to a depth of 250mm, this time moving the loosened soil into the first trench.
- Loosen the bottom soil in the second trench, again adding manure or compost and organic bone meal.
- At this point, start a third trench, moving its topsoil to the second trench and so on, until the entire bed is renched, finally putting the topsoil from the first trench onto the loosened base of the last trench.
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| Trenching Divide your garden bed into a grid, dig up 250mm of topsoil in one block and place it to one side of the bed (A); loosen the soil below this (B) and dig in the recommended fertilizers. |
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| Now dig the next trench, removing 250mm of topsoil and using it to fill in the first trench (C). Repeat the process of enriching and loosening the soil. |
